feat: big refactor to fight fundamental crashes

Some rather foundational things were fundamentally broken, especially related to the initialization procedures of fields / cached properties.

- We completely revamped `bl_cache`, fixing many to-be-discovered bugs.
- We completely streamlined `BLField` property logic into reusable
  `bl_cache.BLProp` and `bl_cache.BLPropType`.
- We implemented `BLInstance` superclass to handle ex. deterministic
  persistance of dynamic enum items, and other nuanced common
  functionality that was being duplicated raw.
- We implemented inter `cached_bl_property` / `BLField` dependency
  logic, including the ability to invalidate dynamic enums without
  @on_value_changed logic. This **greatly** simplifies a vast quantity
  of nodes that were traditionally very difficult to get working due to
  the sharp edges imposed by needing manual invalidation logic.
- We gave `ExprSocket` a significant usability upgrade, including
  thorough parsing logic in the `SocketDef`.

It's not that existing nodes are as such broken, but their existing bugs
are now going to cause problems a lot faster.
Which is a good thing.

BREAKING CHANGE: Closes #13. Closes #16. Big work on #64. Work on #37.

src/blender_maxwell/contracts/__init__.py

@@ -36,6 +36,7 @@ from .bl import (
 	PresetName,
 	SocketName,
 )
+from .bl_types import BLEnumStrEnum
 from .operator_types import (
 	OperatorType,
 )
@@ -64,6 +65,9 @@ __all__ = [
 	'ManagedObjName',
 	'PresetName',
 	'SocketName',
+	'BLEnumStrEnum',
+	'BLInstance',
+	'InstanceID',
 	'OperatorType',
 	'PanelType',
 ]

src/blender_maxwell/contracts/bl_types.py

@@ -0,0 +1,28 @@
+# blender_maxwell
+# Copyright (C) 2024 blender_maxwell Project Contributors
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import typing as typ
+
+
+####################
+# - Blender Enum (w/EnumProperty support)
+####################
+class BLEnumStrEnum(typ.Protocol):
+	@staticmethod
+	def to_name(value: typ.Self) -> str: ...
+
+	@staticmethod
+	def to_icon(value: typ.Self) -> str: ...

src/blender_maxwell/node_trees/maxwell_sim_nodes/bl_socket_map.py

@@ -44,7 +44,7 @@ def socket_def_from_bl_isocket(
 		## -> Accounts for any combo of shape/MathType/PhysicalType.
 		if blsck_info.socket_type == ct.SocketType.Expr:
 			return sockets.ExprSocketDef(
-				shape=blsck_info.size.shape,
+				size=blsck_info.size,
 				mathtype=blsck_info.mathtype,
 				physical_type=blsck_info.physical_type,
 				default_unit=ct.UNITS_BLENDER[blsck_info.physical_type],

src/blender_maxwell/node_trees/maxwell_sim_nodes/contracts/__init__.py

@@ -50,6 +50,7 @@ from .flow_kinds import (
 	LazyArrayRangeFlow,
 	LazyValueFuncFlow,
 	ParamsFlow,
+	ScalingMode,
 	ValueFlow,
 )
 from .flow_signals import FlowSignal
@@ -116,6 +117,7 @@ __all__ = [
 	'LazyArrayRangeFlow',
 	'LazyValueFuncFlow',
 	'ParamsFlow',
+	'ScalingMode',
 	'ValueFlow',
 	'FlowSignal',
 ]

src/blender_maxwell/node_trees/maxwell_sim_nodes/contracts/flow_kinds/__init__.py

@@ -18,7 +18,7 @@ from .array import ArrayFlow
 from .capabilities import CapabilitiesFlow
 from .flow_kinds import FlowKind
 from .info import InfoFlow
-from .lazy_array_range import LazyArrayRangeFlow
+from .lazy_array_range import LazyArrayRangeFlow, ScalingMode
 from .lazy_value_func import LazyValueFuncFlow
 from .params import ParamsFlow
 from .value import ValueFlow
@@ -29,6 +29,7 @@ __all__ = [
 	'FlowKind',
 	'InfoFlow',
 	'LazyArrayRangeFlow',
+	'ScalingMode',
 	'LazyValueFuncFlow',
 	'ParamsFlow',
 	'ValueFlow',

src/blender_maxwell/node_trees/maxwell_sim_nodes/contracts/flow_kinds/array.py

@@ -96,7 +96,8 @@ class ArrayFlow:
 		msg = f'Tried to correct unit of unitless LazyDataValueRange "{corrected_unit}"'
 		raise ValueError(msg)
 
-	def rescale_to_unit(self, unit: spu.Quantity) -> typ.Self:
+	def rescale_to_unit(self, unit: spu.Quantity | None) -> typ.Self:
+		## TODO: Cache by unit would be a very nice speedup for Viz node.
 		if self.unit is not None:
 			return ArrayFlow(
 				values=float(spux.scaling_factor(self.unit, unit)) * self.values,
@@ -104,8 +105,8 @@ class ArrayFlow:
 				is_sorted=self.is_sorted,
 			)
 
+		if unit is None:
+			return self
+
 		msg = f'Tried to rescale unitless LazyDataValueRange to unit {unit}'
 		raise ValueError(msg)
-
-	def rescale_to_unit_system(self, unit: spu.Quantity) -> typ.Self:
-		raise NotImplementedError

src/blender_maxwell/node_trees/maxwell_sim_nodes/contracts/flow_kinds/flow_kinds.py

@@ -62,6 +62,9 @@ class FlowKind(enum.StrEnum):
 	Params = enum.auto()
 	Info = enum.auto()
 
+	####################
+	# - Class Methods
+	####################
 	@classmethod
 	def scale_to_unit_system(
 		cls,
@@ -85,3 +88,43 @@ class FlowKind(enum.StrEnum):
 
 		msg = 'Tried to scale unknown kind'
 		raise ValueError(msg)
+
+	####################
+	# - Computed
+	####################
+	@property
+	def flow_kind(self) -> str:
+		return {
+			FlowKind.Value: FlowKind.Value,
+			FlowKind.Array: FlowKind.Array,
+			FlowKind.LazyValueFunc: FlowKind.LazyValueFunc,
+			FlowKind.LazyArrayRange: FlowKind.LazyArrayRange,
+		}[self]
+
+	@property
+	def socket_shape(self) -> str:
+		return {
+			FlowKind.Value: 'CIRCLE',
+			FlowKind.Array: 'SQUARE',
+			FlowKind.LazyArrayRange: 'SQUARE',
+			FlowKind.LazyValueFunc: 'DIAMOND',
+		}[self]
+
+	####################
+	# - Blender Enum
+	####################
+	@staticmethod
+	def to_name(v: typ.Self) -> str:
+		return {
+			FlowKind.Capabilities: 'Capabilities',
+			FlowKind.Value: 'Value',
+			FlowKind.Array: 'Array',
+			FlowKind.LazyArrayRange: 'Range',
+			FlowKind.LazyValueFunc: 'Lazy Value',
+			FlowKind.Params: 'Parameters',
+			FlowKind.Info: 'Information',
+		}[v]
+
+	@staticmethod
+	def to_icon(_: typ.Self) -> str:
+		return ''

src/blender_maxwell/node_trees/maxwell_sim_nodes/contracts/flow_kinds/lazy_array_range.py

@@ -15,6 +15,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import dataclasses
+import enum
 import functools
 import typing as typ
 from types import MappingProxyType
@@ -33,6 +34,25 @@ from .lazy_value_func import LazyValueFuncFlow
 log = logger.get(__name__)
 
 
+class ScalingMode(enum.StrEnum):
+	Lin = enum.auto()
+	Geom = enum.auto()
+	Log = enum.auto()
+
+	@staticmethod
+	def to_name(v: typ.Self) -> str:
+		SM = ScalingMode
+		return {
+			SM.Lin: 'Linear',
+			SM.Geom: 'Geometric',
+			SM.Log: 'Logarithmic',
+		}[v]
+
+	@staticmethod
+	def to_icon(_: typ.Self) -> str:
+		return ''
+
+
 @dataclasses.dataclass(frozen=True, kw_only=True)
 class LazyArrayRangeFlow:
 	r"""Represents a linearly/logarithmically spaced array using symbolic boundary expressions, with support for units and lazy evaluation.
@@ -84,7 +104,7 @@ class LazyArrayRangeFlow:
 	start: spux.ScalarUnitlessComplexExpr
 	stop: spux.ScalarUnitlessComplexExpr
 	steps: int
-	scaling: typ.Literal['lin', 'geom', 'log'] = 'lin'
+	scaling: ScalingMode = ScalingMode.Lin
 
 	unit: spux.Unit | None = None
 
@@ -295,9 +315,9 @@ class LazyArrayRangeFlow:
 			A `jax` function that takes a valid `start`, `stop`, and `steps`, and returns a 1D `jax` array.
 		"""
 		jnp_nspace = {
-			'lin': jnp.linspace,
-			'geom': jnp.geomspace,
-			'log': jnp.logspace,
+			ScalingMode.Lin: jnp.linspace,
+			ScalingMode.Geom: jnp.geomspace,
+			ScalingMode.Log: jnp.logspace,
 		}.get(self.scaling)
 		if jnp_nspace is None:
 			msg = f'ArrayFlow scaling method {self.scaling} is unsupported'

src/blender_maxwell/node_trees/maxwell_sim_nodes/node_tree.py

@@ -430,17 +430,40 @@ class MaxwellSimTree(bpy.types.NodeTree):
 ####################
 # - Post-Load Handler
 ####################
-def initialize_sim_tree_node_link_cache(_: bpy.types.Scene):
+@bpy.app.handlers.persistent
+def initialize_sim_tree_node_link_cache(_):
 	"""Whenever a file is loaded, create/regenerate the NodeLinkCache in all trees."""
 	for node_tree in bpy.data.node_groups:
 		if node_tree.bl_idname == 'MaxwellSimTree':
 			node_tree.on_load()
 
 
+@bpy.app.handlers.persistent
+def populate_missing_persistence(_) -> None:
+	"""For all nodes and sockets with elements that don't have persistent elements computed, compute them.
+
+	This is used when new dynamic enum properties are added to nodes and sockets, which need to first be computed and persisted in a context where setting properties is allowed.
+	"""
+	# Iterate over MaxwellSim Trees
+	for node_tree in [
+		_node_tree
+		for _node_tree in bpy.data.node_groups
+		if _node_tree.bl_idname == ct.TreeType.MaxwellSim.value and _node_tree.is_active
+	]:
+		# Iterate over MaxwellSim Nodes
+		# -> Excludes ex. frame and reroute nodes.
+		for node in [_node for _node in node_tree.nodes if hasattr(_node, 'node_type')]:
+			node.regenerate_dynamic_field_persistance()
+			for bl_sockets in [node.inputs, node.outputs]:
+				for bl_socket in bl_sockets:
+					bl_socket.regenerate_dynamic_field_persistance()
+
+
 ####################
 # - Blender Registration
 ####################
 bpy.app.handlers.load_post.append(initialize_sim_tree_node_link_cache)
+bpy.app.handlers.load_post.append(populate_missing_persistence)
 ## TODO: Move to top-level registration.
 
 BL_REGISTER = [

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/analysis/extract_data.py

@@ -67,8 +67,7 @@ class ExtractDataNode(base.MaxwellSimNode):
 	####################
 	# - Properties
 	####################
-	extract_filter: enum.Enum = bl_cache.BLField(
-		prop_ui=True,
+	extract_filter: enum.StrEnum = bl_cache.BLField(
 		enum_cb=lambda self, _: self.search_extract_filters(),
 	)
 

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/analysis/math/filter_math.py

@@ -126,10 +126,10 @@ class FilterMathNode(base.MaxwellSimNode):
 	bl_label = 'Filter Math'
 
 	input_sockets: typ.ClassVar = {
-		'Expr': sockets.ExprSocketDef(active_kind=ct.FlowKind.Array),
+		'Expr': sockets.ExprSocketDef(active_kind=ct.FlowKind.LazyValueFunc),
 	}
 	output_sockets: typ.ClassVar = {
-		'Expr': sockets.ExprSocketDef(active_kind=ct.FlowKind.Array),
+		'Expr': sockets.ExprSocketDef(active_kind=ct.FlowKind.LazyValueFunc),
 	}
 
 	####################
@@ -141,12 +141,8 @@ class FilterMathNode(base.MaxwellSimNode):
 	)
 
 	# Dimension Selection
-	dim_0: enum.Enum = bl_cache.BLField(
-		None, prop_ui=True, enum_cb=lambda self, _: self.search_dims()
-	)
-	dim_1: enum.Enum = bl_cache.BLField(
-		None, prop_ui=True, enum_cb=lambda self, _: self.search_dims()
-	)
+	dim_0: enum.StrEnum = bl_cache.BLField(enum_cb=lambda self, _: self.search_dims())
+	dim_1: enum.StrEnum = bl_cache.BLField(enum_cb=lambda self, _: self.search_dims())
 
 	####################
 	# - Computed
@@ -259,14 +255,14 @@ class FilterMathNode(base.MaxwellSimNode):
 			# Determine Whether to Declare New Loose Input SOcket
 			if (
 				current_bl_socket is None
-				or current_bl_socket.shape is not None
+				or current_bl_socket.size is not spux.NumberSize1D.Scalar
 				or current_bl_socket.physical_type != pinned_physical_type
 				or current_bl_socket.mathtype != wanted_mathtype
 			):
 				self.loose_input_sockets = {
 					'Value': sockets.ExprSocketDef(
 						active_kind=ct.FlowKind.Value,
-						shape=None,
+						size=spux.NumberSize1D.Scalar,
 						physical_type=pinned_physical_type,
 						mathtype=wanted_mathtype,
 						default_unit=pinned_unit,

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/analysis/math/map_math.py

@@ -364,10 +364,10 @@ class MapMathNode(base.MaxwellSimNode):
 	bl_label = 'Map Math'
 
 	input_sockets: typ.ClassVar = {
-		'Expr': sockets.ExprSocketDef(active_kind=ct.FlowKind.Array),
+		'Expr': sockets.ExprSocketDef(active_kind=ct.FlowKind.LazyValueFunc),
 	}
 	output_sockets: typ.ClassVar = {
-		'Expr': sockets.ExprSocketDef(active_kind=ct.FlowKind.Array),
+		'Expr': sockets.ExprSocketDef(active_kind=ct.FlowKind.LazyValueFunc),
 	}
 
 	####################

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/analysis/math/operate_math.py

@@ -71,22 +71,22 @@ class OperateMathNode(base.MaxwellSimNode):
 	bl_label = 'Operate Math'
 
 	input_sockets: typ.ClassVar = {
-		'Expr L': sockets.ExprSocketDef(active_kind=ct.FlowKind.Array),
-		'Expr R': sockets.ExprSocketDef(active_kind=ct.FlowKind.Array),
+		'Expr L': sockets.ExprSocketDef(active_kind=ct.FlowKind.LazyValueFunc),
+		'Expr R': sockets.ExprSocketDef(active_kind=ct.FlowKind.LazyValueFunc),
 	}
 	output_sockets: typ.ClassVar = {
-		'Expr': sockets.ExprSocketDef(active_kind=ct.FlowKind.Array),
+		'Expr': sockets.ExprSocketDef(active_kind=ct.FlowKind.LazyValueFunc),
 	}
 
 	####################
 	# - Properties
 	####################
-	category: enum.Enum = bl_cache.BLField(
-		prop_ui=True, enum_cb=lambda self, _: self.search_categories()
+	category: enum.StrEnum = bl_cache.BLField(
+		enum_cb=lambda self, _: self.search_categories()
 	)
 
-	operation: enum.Enum = bl_cache.BLField(
-		prop_ui=True, enum_cb=lambda self, _: self.search_operations()
+	operation: enum.StrEnum = bl_cache.BLField(
+		enum_cb=lambda self, _: self.search_operations()
 	)
 
 	def search_categories(self) -> list[ct.BLEnumElement]:

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/analysis/math/transform_math.py

@@ -62,8 +62,8 @@ class TransformMathNode(base.MaxwellSimNode):
 	####################
 	# - Properties
 	####################
-	operation: enum.Enum = bl_cache.BLField(
-		prop_ui=True, enum_cb=lambda self, _: self.search_operations()
+	operation: enum.StrEnum = bl_cache.BLField(
+		enum_cb=lambda self, _: self.search_operations()
 	)
 
 	def search_operations(self) -> list[ct.BLEnumElement]:

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/analysis/viz.py

@@ -209,7 +209,7 @@ class VizNode(base.MaxwellSimNode):
 	####################
 	input_sockets: typ.ClassVar = {
 		'Expr': sockets.ExprSocketDef(
-			active_kind=ct.FlowKind.Array,
+			active_kind=ct.FlowKind.LazyValueFunc,
 			symbols={_x := sp.Symbol('x', real=True)},
 			default_value=2 * _x,
 		),
@@ -225,31 +225,33 @@ class VizNode(base.MaxwellSimNode):
 	#####################
 	## - Properties
 	#####################
-	viz_mode: enum.Enum = bl_cache.BLField(
-		prop_ui=True, enum_cb=lambda self, _: self.search_viz_modes()
-	)
-	viz_target: enum.Enum = bl_cache.BLField(
-		prop_ui=True, enum_cb=lambda self, _: self.search_targets()
-	)
-
-	# Mode-Dependent Properties
-	colormap: image_ops.Colormap = bl_cache.BLField(
-		image_ops.Colormap.Viridis, prop_ui=True
-	)
-
-	#####################
-	## - Mode Searcher
-	#####################
-	@property
-	def data_info(self) -> ct.InfoFlow | None:
+	@bl_cache.cached_bl_property()
+	def input_info(self) -> ct.InfoFlow | None:
 		info = self._compute_input('Expr', kind=ct.FlowKind.Info)
 		if not ct.FlowSignal.check(info):
 			return info
 
 		return None
 
+	viz_mode: enum.StrEnum = bl_cache.BLField(
+		enum_cb=lambda self, _: self.search_viz_modes(),
+		cb_depends_on={'input_info'},
+	)
+	viz_target: enum.StrEnum = bl_cache.BLField(
+		enum_cb=lambda self, _: self.search_targets(),
+		cb_depends_on={'viz_mode'},
+	)
+
+	# Mode-Dependent Properties
+	colormap: image_ops.Colormap = bl_cache.BLField(
+		image_ops.Colormap.Viridis,
+	)
+
+	#####################
+	## - Searchers
+	#####################
 	def search_viz_modes(self) -> list[ct.BLEnumElement]:
-		if self.data_info is not None:
+		if self.input_info is not None:
 			return [
 				(
 					viz_mode,
@@ -258,14 +260,11 @@ class VizNode(base.MaxwellSimNode):
 					VizMode.to_icon(viz_mode),
 					i,
 				)
-				for i, viz_mode in enumerate(VizMode.valid_modes_for(self.data_info))
+				for i, viz_mode in enumerate(VizMode.valid_modes_for(self.input_info))
 			]
 
 		return []
 
-	#####################
-	## - Target Searcher
-	#####################
 	def search_targets(self) -> list[ct.BLEnumElement]:
 		if self.viz_mode is not None:
 			return [
@@ -302,20 +301,14 @@ class VizNode(base.MaxwellSimNode):
 		input_sockets_optional={'Expr': True},
 	)
 	def on_any_changed(self, input_sockets: dict):
+		self.input_info = bl_cache.Signal.InvalidateCache
+
 		info = input_sockets['Expr'][ct.FlowKind.Info]
 		params = input_sockets['Expr'][ct.FlowKind.Params]
 
 		has_info = not ct.FlowSignal.check(info)
 		has_params = not ct.FlowSignal.check(params)
 
-		# Reset Viz Mode/Target
-		has_nonpending_info = not ct.FlowSignal.check_single(
-			info, ct.FlowSignal.FlowPending
-		)
-		if has_nonpending_info:
-			self.viz_mode = bl_cache.Signal.ResetEnumItems
-			self.viz_target = bl_cache.Signal.ResetEnumItems
-
 		# Provide Sockets for Symbol Realization
 		## -> This happens if Params contains not-yet-realized symbols.
 		if has_info and has_params and params.symbols:
@@ -325,7 +318,7 @@ class VizNode(base.MaxwellSimNode):
 				self.loose_input_sockets = {
 					sym.name: sockets.ExprSocketDef(
 						active_kind=ct.FlowKind.LazyArrayRange,
-						shape=None,
+						size=spux.NumberSize1D.Scalar,
 						mathtype=info.dim_mathtypes[sym.name],
 						physical_type=info.dim_physical_types[sym.name],
 						default_min=(
@@ -340,22 +333,13 @@ class VizNode(base.MaxwellSimNode):
 						),
 						default_steps=50,
 					)
-					for sym in sorted(
-						params.symbols, key=lambda el: info.dim_names.index(el.name)
-					)
+					for sym in params.sorted_symbols
 					if sym.name in info.dim_names
 				}
 
 		elif self.loose_input_sockets:
 			self.loose_input_sockets = {}
 
-	@events.on_value_changed(
-		prop_name='viz_mode',
-		run_on_init=True,
-	)
-	def on_viz_mode_changed(self):
-		self.viz_target = bl_cache.Signal.ResetEnumItems
-
 	#####################
 	## - Plotting
 	#####################
@@ -374,12 +358,15 @@ class VizNode(base.MaxwellSimNode):
 		self, managed_objs, props, input_sockets, loose_input_sockets, unit_systems
 	):
 		# Retrieve Inputs
+		lazy_value_func = input_sockets['Expr'][ct.FlowKind.LazyValueFunc]
 		info = input_sockets['Expr'][ct.FlowKind.Info]
 		params = input_sockets['Expr'][ct.FlowKind.Params]
 
 		has_info = not ct.FlowSignal.check(info)
 		has_params = not ct.FlowSignal.check(params)
 
+		# Invalid Mode | Target
+		## -> To limit branching, return now if things aren't right.
 		if (
 			not has_info
 			or not has_params
@@ -388,18 +375,21 @@ class VizNode(base.MaxwellSimNode):
 		):
 			return
 
-		# Compute Data
-		lazy_value_func = input_sockets['Expr'][ct.FlowKind.LazyValueFunc]
-		symbol_values = (
-			loose_input_sockets
-			if not params.symbols
-			else {
-				sym: loose_input_sockets[sym.name]
+		# Compute LazyArrayRanges for Symbols from Loose Sockets
+		## -> These are the concrete values of the symbol for plotting.
+		## -> In a quite nice turn of events, all this is cached lookups.
+		## -> ...Unless something changed, in which case, well. It changed.
+		symbol_values = {
+			sym: (
+				loose_input_sockets[sym.name]
 				.realize_array.rescale_to_unit(info.dim_units[sym.name])
 				.values
+			)
 			for sym in params.sorted_symbols
 		}
-		)
+
+		# Realize LazyValueFunc w/Symbolic Values, Unit System
+		## -> This gives us the actual plot data!
 		data = lazy_value_func.func_jax(
 			*params.scaled_func_args(
 				unit_systems['BlenderUnits'], symbol_values=symbol_values
@@ -408,6 +398,9 @@ class VizNode(base.MaxwellSimNode):
 				unit_systems['BlenderUnits'], symbol_values=symbol_values
 			),
 		)
+
+		# Replace InfoFlow Indices w/Realized Symbolic Ranges
+		## -> This ensures correct axis scaling.
 		if params.symbols:
 			info = info.rescale_dim_idxs(loose_input_sockets)
 
@@ -417,6 +410,7 @@ class VizNode(base.MaxwellSimNode):
 				lambda ax: VizMode.to_plotter(props['viz_mode'])(data, info, ax),
 				bl_select=True,
 			)
+
 		if props['viz_target'] == VizTarget.Pixels:
 			managed_objs['plot'].map_2d_to_image(
 				data,

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/base.py

@@ -20,17 +20,15 @@ Attributes:
 	MANDATORY_PROPS: Properties that must be defined on the `MaxwellSimNode`.
 """
 
-## TODO: Check whether input_socket_sets and output_socket_sets have the right shape? Or just use a type checker...
-
+import enum
 import typing as typ
-import uuid
 from collections import defaultdict
 from types import MappingProxyType
 
 import bpy
 import sympy as sp
 
-from blender_maxwell.utils import bl_cache, logger
+from blender_maxwell.utils import bl_cache, bl_instance, logger
 
 from .. import contracts as ct
 from .. import managed_objs as _managed_objs
@@ -40,10 +38,20 @@ from . import presets as _presets
 
 log = logger.get(__name__)
 
+####################
+# - Types
+####################
+Sockets: typ.TypeAlias = dict[str, sockets.base.SocketDef]
+Preset: typ.TypeAlias = dict[str, _presets.PresetDef]
+ManagedObjs: typ.TypeAlias = dict[ct.ManagedObjName, type[_managed_objs.ManagedObj]]
+
 MANDATORY_PROPS: set[str] = {'node_type', 'bl_label'}
 
 
-class MaxwellSimNode(bpy.types.Node):
+####################
+# - Node
+####################
+class MaxwellSimNode(bpy.types.Node, bl_instance.BLInstance):
 	"""A specialized Blender node for Maxwell simulations.
 
 	Attributes:
@@ -58,100 +66,111 @@ class MaxwellSimNode(bpy.types.Node):
 		locked: Whether the node is currently 'locked' aka. non-editable.
 	"""
 
+	####################
+	# - Properties
+	####################
+	node_type: ct.NodeType
+	bl_label: str
+
+	# Features
 	use_sim_node_name: bool = False
-	## TODO: bl_description from first line of __doc__?
 
-	# Sockets
-	input_sockets: typ.ClassVar[dict[str, sockets.base.SocketDef]] = MappingProxyType(
-		{}
-	)
-	output_sockets: typ.ClassVar[dict[str, sockets.base.SocketDef]] = MappingProxyType(
-		{}
-	)
-	input_socket_sets: typ.ClassVar[dict[str, dict[str, sockets.base.SocketDef]]] = (
-		MappingProxyType({})
-	)
-	output_socket_sets: typ.ClassVar[dict[str, dict[str, sockets.base.SocketDef]]] = (
-		MappingProxyType({})
+	# Declarations
+	input_sockets: typ.ClassVar[Sockets] = MappingProxyType({})
+	output_sockets: typ.ClassVar[Sockets] = MappingProxyType({})
+
+	input_socket_sets: typ.ClassVar[dict[str, Sockets]] = MappingProxyType({})
+	output_socket_sets: typ.ClassVar[dict[str, Sockets]] = MappingProxyType({})
+
+	managed_obj_types: typ.ClassVar[ManagedObjs] = MappingProxyType({})
+	presets: typ.ClassVar[dict[str, Preset]] = MappingProxyType({})
+
+	## __init_subclass__ Computed
+	bl_idname: str
+
+	####################
+	# - Fields
+	####################
+	sim_node_name: str = bl_cache.BLField('')
+
+	# Loose Sockets
+	loose_input_sockets: dict[str, sockets.base.SocketDef] = bl_cache.BLField({})
+	loose_output_sockets: dict[str, sockets.base.SocketDef] = bl_cache.BLField({})
+
+	# UI Options
+	preview_active: bool = bl_cache.BLField(False)
+	locked: bool = bl_cache.BLField(False, use_prop_update=False)
+
+	# Active Socket Set
+	active_socket_set: enum.StrEnum = bl_cache.BLField(
+		enum_cb=lambda self, _: self.socket_sets_bl_enum()
 	)
 
-	# Presets
-	presets: typ.ClassVar[dict[str, dict[str, _presets.PresetDef]]] = MappingProxyType(
-		{}
+	@classmethod
+	def socket_sets_bl_enum(cls) -> list[ct.BLEnumElement]:
+		return [
+			(socket_set_name, socket_set_name, socket_set_name, '', i)
+			for i, socket_set_name in enumerate(cls.socket_set_names())
+		]
+
+	# Active Preset
+	active_preset: enum.StrEnum = bl_cache.BLField(
+		enum_cb=lambda self, _: self.presets_bl_enum()
 	)
 
-	# Managed Objects
-	managed_obj_types: typ.ClassVar[
-		dict[ct.ManagedObjName, type[_managed_objs.ManagedObj]]
-	] = MappingProxyType({})
+	@classmethod
+	def presets_bl_enum(cls) -> list[ct.BLEnumElement]:
+		return [
+			(
+				preset_name,
+				preset_def.label,
+				preset_def.description,
+				'',
+				i,
+			)
+			for i, (preset_name, preset_def) in enumerate(cls.presets.items())
+		]
 
-	def reset_instance_id(self) -> None:
-		self.instance_id = str(uuid.uuid4())
+	####################
+	# - Managed Objects
+	####################
+	@bl_cache.cached_bl_property(depends_on={'sim_node_name'})
+	def managed_objs(self) -> dict[str, _managed_objs.ManagedObj]:
+		"""Access the constructed managed objects defined in `self.managed_obj_types`.
 
-	# BLFields
-	blfields: typ.ClassVar[dict[str, str]] = MappingProxyType({})
-	ui_blfields: typ.ClassVar[set[str]] = frozenset()
+		Managed objects are special in that they **don't keep any non-reproducible state**.
+		In fact, all managed object state can generally be derived entirely from the managed object's `name` attribute.
+		As a result, **consistency in namespacing is of the utmost importance**, if reproducibility of managed objects is to be guaranteed.
+
+		This name must be in sync with the name of the managed "thing", which is where this computed property comes in.
+		The node's half of the responsibility is to push a new name whenever `self.sim_node_name` changes.
+		"""
+		if self.managed_obj_types:
+			return {
+				mobj_name: mobj_type(self.sim_node_name)
+				for mobj_name, mobj_type in self.managed_obj_types.items()
+			}
+
+		return {}
 
 	####################
 	# - Class Methods
 	####################
 	@classmethod
-	def _assert_attrs_valid(cls) -> None:
-		"""Asserts that all mandatory attributes are defined on the class.
-
-		The list of mandatory objects is sourced from `base.MANDATORY_PROPS`.
-
-		Raises:
-			ValueError: If a mandatory attribute defined in `base.MANDATORY_PROPS` is not defined on the class.
-		"""
-		for cls_attr in MANDATORY_PROPS:
-			if not hasattr(cls, cls_attr):
-				msg = f'Node class {cls} does not define mandatory attribute "{cls_attr}".'
-				raise ValueError(msg)
-
-	@classmethod
-	def declare_blfield(
-		cls, attr_name: str, bl_attr_name: str, prop_ui: bool = False
-	) -> None:
-		cls.blfields = cls.blfields | {attr_name: bl_attr_name}
-
-		if prop_ui:
-			cls.ui_blfields = cls.ui_blfields | {attr_name}
-
-	@classmethod
-	def set_prop(
-		cls,
-		prop_name: str,
-		prop: bpy.types.Property,
-		no_update: bool = False,
-		update_with_name: str | None = None,
-		**kwargs,
-	) -> None:
-		"""Adds a Blender property to a class via `__annotations__`, so it initializes with any subclass.
+	def socket_set_names(cls) -> list[str]:
+		"""Retrieve the names of socket sets, in an order-preserving way.
 
 		Notes:
-			- Blender properties can't be set within `__init_subclass__` simply by adding attributes to the class; they must be added as type annotations.
-			- Must be called **within** `__init_subclass__`.
+			Semantically similar to `list(set(...) | set(...))`.
 
-		Parameters:
-			name: The name of the property to set.
-			prop: The `bpy.types.Property` to instantiate and attach..
-			no_update: Don't attach a `self.on_prop_changed()` callback to the property's `update`.
+		Returns:
+			List of socket set names, without duplicates, in definition order.
 		"""
-		_update_with_name = prop_name if update_with_name is None else update_with_name
-		extra_kwargs = (
-			{
-				'update': lambda self, context: self.on_prop_changed(
-					_update_with_name, context
-				),
-			}
-			if not no_update
-			else {}
-		)
-		cls.__annotations__[prop_name] = prop(
-			**kwargs,
-			**extra_kwargs,
-		)
+		return (_input_socket_set_names := list(cls.input_socket_sets.keys())) + [
+			output_socket_set_name
+			for output_socket_set_name in cls.output_socket_sets
+			if output_socket_set_name not in _input_socket_set_names
+		]
 
 	@classmethod
 	def _gather_event_methods(cls) -> dict[str, typ.Callable[[], None]]:
@@ -169,6 +188,7 @@ class MaxwellSimNode(bpy.types.Node):
 			for attr_name in dir(cls)
 			if hasattr(method := getattr(cls, attr_name), 'event')
 			and method.event in set(ct.FlowEvent)
+			## Forbidding blfields prevents triggering __get__ on bl_property
 		]
 		event_methods_by_event = {event: [] for event in set(ct.FlowEvent)}
 		for method in event_methods:
@@ -176,22 +196,6 @@ class MaxwellSimNode(bpy.types.Node):
 
 		return event_methods_by_event
 
-	@classmethod
-	def socket_set_names(cls) -> list[str]:
-		"""Retrieve the names of socket sets, in an order-preserving way.
-
-		Notes:
-			Semantically similar to `list(set(...) | set(...))`.
-
-		Returns:
-			List of socket set names, without duplicates, in definition order.
-		"""
-		return (_input_socket_set_names := list(cls.input_socket_sets.keys())) + [
-			output_socket_set_name
-			for output_socket_set_name in cls.output_socket_sets
-			if output_socket_set_name not in _input_socket_set_names
-		]
-
 	####################
 	# - Subclass Initialization
 	####################
@@ -204,64 +208,20 @@ class MaxwellSimNode(bpy.types.Node):
 		"""
 		log.debug('Initializing Node: %s', cls.node_type)
 		super().__init_subclass__(**kwargs)
-		cls._assert_attrs_valid()
+
+		# Check Attribute Validity
+		cls.assert_attrs_valid(MANDATORY_PROPS)
 
 		# Node Properties
-		## Identifiers
 		cls.bl_idname: str = str(cls.node_type.value)
-		cls.set_prop('instance_id', bpy.props.StringProperty, no_update=True)
-		cls.set_prop('sim_node_name', bpy.props.StringProperty, default='')
-
-		## Special States
-		cls.set_prop('preview_active', bpy.props.BoolProperty, default=False)
-		cls.set_prop('locked', bpy.props.BoolProperty, no_update=True, default=False)
-
-		## Event Method Callbacks
 		cls.event_methods_by_event = cls._gather_event_methods()
 
-		## Active Socket Set
-		if len(cls.input_socket_sets) + len(cls.output_socket_sets) > 0:
-			socket_set_names = cls.socket_set_names()
-			cls.set_prop(
-				'active_socket_set',
-				bpy.props.EnumProperty,
-				name='Active Socket Set',
-				items=[
-					(socket_set_name, socket_set_name, socket_set_name)
-					for socket_set_name in socket_set_names
-				],
-				default=socket_set_names[0],
-			)
-		else:
-			cls.active_socket_set = None
-
-		## Active Preset
-		## TODO: Validate Presets
-		if cls.presets:
-			cls.set_prop(
-				'active_preset',
-				bpy.props.EnumProperty,
-				name='Active Preset',
-				description='The currently active preset',
-				items=[
-					(
-						preset_name,
-						preset_def.label,
-						preset_def.description,
-					)
-					for preset_name, preset_def in cls.presets.items()
-				],
-				default=next(cls.presets.keys()),
-			)
-		else:
-			cls.active_preset = None
-
 	####################
-	# - Events: Default
+	# - Events: Sim Node Name | Active Socket Set | Active Preset
 	####################
 	@events.on_value_changed(
 		prop_name='sim_node_name',
-		props={'sim_node_name'},
+		props={'sim_node_name', 'managed_objs'},
 		stop_propagation=True,
 	)
 	def _on_sim_node_name_changed(self, props):
@@ -273,7 +233,7 @@ class MaxwellSimNode(bpy.types.Node):
 		)
 
 		# Set Name of Managed Objects
-		for mobj in self.managed_objs.values():
+		for mobj in props['managed_objs'].values():
 			mobj.name = props['sim_node_name']
 
 		## Invalidate Cache
@@ -290,7 +250,10 @@ class MaxwellSimNode(bpy.types.Node):
 		self._sync_sockets()
 
 	@events.on_value_changed(
-		prop_name='active_preset', props=['presets', 'active_preset']
+		prop_name='active_preset',
+		run_on_init=True,
+		props={'presets', 'active_preset'},
+		stop_propagation=True,
 	)
 	def _on_active_preset_changed(self, props: dict):
 		if props['active_preset'] is not None:
@@ -313,6 +276,9 @@ class MaxwellSimNode(bpy.types.Node):
 				## TODO: Account for FlowKind
 				bl_socket.value = socket_value
 
+	####################
+	# - Events: Preview | Plot
+	####################
 	@events.on_show_plot(stop_propagation=False)
 	def _on_show_plot(self):
 		node_tree = self.id_data
@@ -339,6 +305,9 @@ class MaxwellSimNode(bpy.types.Node):
 			for mobj in self.managed_objs.values():
 				mobj.hide_preview()
 
+	####################
+	# - Events: Lock
+	####################
 	@events.on_enable_lock()
 	def _on_enabled_lock(self):
 		# Set Locked to Active
@@ -354,11 +323,8 @@ class MaxwellSimNode(bpy.types.Node):
 		self.locked = False
 
 	####################
-	# - Loose Sockets w/Events
+	# - Events: Loose Sockets
 	####################
-	loose_input_sockets: dict[str, sockets.base.SocketDef] = bl_cache.BLField({})
-	loose_output_sockets: dict[str, sockets.base.SocketDef] = bl_cache.BLField({})
-
 	@events.on_value_changed(prop_name={'loose_input_sockets', 'loose_output_sockets'})
 	def _on_loose_sockets_changed(self):
 		self._sync_sockets()
@@ -516,23 +482,6 @@ class MaxwellSimNode(bpy.types.Node):
 		self._prune_inactive_sockets()
 		self._add_new_active_sockets()
 
-	####################
-	# - Managed Objects
-	####################
-	@bl_cache.cached_bl_property(persist=True)
-	def managed_objs(self) -> dict[str, _managed_objs.ManagedObj]:
-		"""Access the managed objects defined on this node.
-
-		Persistent cache ensures that the managed objects are only created on first access, even across file reloads.
-		"""
-		if self.managed_obj_types:
-			return {
-				mobj_name: mobj_type(self.sim_node_name)
-				for mobj_name, mobj_type in self.managed_obj_types.items()
-			}
-
-		return {}
-
 	####################
 	# - Event Methods
 	####################
@@ -733,7 +682,7 @@ class MaxwellSimNode(bpy.types.Node):
 			)
 		)
 
-	@bl_cache.cached_bl_property(persist=False)
+	@bl_cache.cached_bl_property()
 	def _dependent_outputs(
 		self,
 	) -> dict[
@@ -904,7 +853,7 @@ class MaxwellSimNode(bpy.types.Node):
 	####################
 	# - Property Event: On Update
 	####################
-	def on_prop_changed(self, prop_name: str, _: bpy.types.Context) -> None:
+	def on_prop_changed(self, prop_name: str) -> None:
 		"""Report that a particular property has changed, which may cause certain caches to regenerate.
 
 		Notes:
@@ -916,10 +865,6 @@ class MaxwellSimNode(bpy.types.Node):
 			prop_name: The name of the property that changed.
 		"""
 		if hasattr(self, prop_name):
-			# Invalidate UI BLField Caches
-			if prop_name in self.ui_blfields:
-				setattr(self, prop_name, bl_cache.Signal.InvalidateCache)
-
 			# Trigger Event
 			self.trigger_event(ct.FlowEvent.DataChanged, prop_name=prop_name)
 		else:
@@ -952,16 +897,16 @@ class MaxwellSimNode(bpy.types.Node):
 			layout.enabled = False
 
 		if self.active_socket_set:
-			layout.prop(self, 'active_socket_set', text='')
+			layout.prop(self, self.blfields['active_socket_set'], text='')
 
 		if self.active_preset is not None:
-			layout.prop(self, 'active_preset', text='')
+			layout.prop(self, self.blfields['active_preset'], text='')
 
 		# Draw Name
 		if self.use_sim_node_name:
 			row = layout.row(align=True)
 			row.label(text='', icon='FILE_TEXT')
-			row.prop(self, 'sim_node_name', text='')
+			row.prop(self, self.blfields['sim_node_name'], text='')
 
 		# Draw Name
 		self.draw_props(context, layout)
@@ -1029,24 +974,20 @@ class MaxwellSimNode(bpy.types.Node):
 		Notes:
 			Run by Blender when a new instance of a node is added to a tree.
 		"""
+		# Initialize Sockets
+		## -> Ensures the availability of static sockets before items/methods.
+		## -> Ensures the availability of static sockets before items/methods.
+		self._sync_sockets()
+
 		# Initialize Instance ID
-		## This is used by various caches from 'bl_cache'.
+		## -> This is used by various caches from 'bl_cache'.
+		## -> Also generates (first-time) the various enums.
 		self.reset_instance_id()
 
 		# Initialize Name
-		## This is used whenever a unique name pointing to this node is needed.
-		## Contrary to self.name, it can be altered by the user as a property.
+		## -> Ensures the availability of sim_node_name immediately.
 		self.sim_node_name = self.name
 
-		# Initialize Sockets
-		## This initializes any nodes that need initializing
-		self._sync_sockets()
-
-		# Apply Preset
-		## This applies the default preset, if any.
-		if self.active_preset:
-			self._on_active_preset_changed()
-
 		# Event Methods
 		## Run any 'DataChanged' methods with 'run_on_init' set.
 		## Semantically: Creating data _arguably_ changes it.

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/bounds/bound_cond_nodes/absorbing_bound_cond.py

@@ -61,7 +61,7 @@ class AdiabAbsorbBoundCondNode(base.MaxwellSimNode):
 	####################
 	input_sockets: typ.ClassVar = {
 		'Layers': sockets.ExprSocketDef(
-			shape=None,
+			size=spux.NumberSize1D.Scalar,
 			mathtype=spux.MathType.Integer,
 			abs_min=1,
 			default_value=40,
@@ -71,14 +71,13 @@ class AdiabAbsorbBoundCondNode(base.MaxwellSimNode):
 		'Simple': {},
 		'Full': {
 			'σ Order': sockets.ExprSocketDef(
-				shape=None,
+				size=spux.NumberSize1D.Scalar,
 				mathtype=spux.MathType.Integer,
 				abs_min=1,
 				default_value=3,
 			),
 			'σ Range': sockets.ExprSocketDef(
-				shape=(2,),
-				mathtype=spux.MathType.Real,
+				size=spux.NumberSize1D.Vec2,
 				default_value=sp.Matrix([0, 1.5]),
 				abs_min=0,
 			),

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/bounds/bound_cond_nodes/pml_bound_cond.py

@@ -64,7 +64,7 @@ class PMLBoundCondNode(base.MaxwellSimNode):
 	####################
 	input_sockets: typ.ClassVar = {
 		'Layers': sockets.ExprSocketDef(
-			shape=None,
+			size=spux.NumberSize1D.Scalar,
 			mathtype=spux.MathType.Integer,
 			abs_min=1,
 			default_value=12,
@@ -74,37 +74,37 @@ class PMLBoundCondNode(base.MaxwellSimNode):
 		'Simple': {},
 		'Full': {
 			'σ Order': sockets.ExprSocketDef(
-				shape=None,
+				size=spux.NumberSize1D.Scalar,
 				mathtype=spux.MathType.Integer,
 				abs_min=1,
 				default_value=3,
 			),
 			'σ Range': sockets.ExprSocketDef(
-				shape=(2,),
+				size=spux.NumberSize1D.Vec2,
 				mathtype=spux.MathType.Real,
 				default_value=sp.Matrix([0, 1.5]),
 				abs_min=0,
 			),
 			'κ Order': sockets.ExprSocketDef(
-				shape=None,
+				size=spux.NumberSize1D.Scalar,
 				mathtype=spux.MathType.Integer,
 				abs_min=1,
 				default_value=3,
 			),
 			'κ Range': sockets.ExprSocketDef(
-				shape=(2,),
+				size=spux.NumberSize1D.Vec2,
 				mathtype=spux.MathType.Real,
 				default_value=sp.Matrix([0, 1.5]),
 				abs_min=0,
 			),
 			'α Order': sockets.ExprSocketDef(
-				shape=None,
+				size=spux.NumberSize1D.Scalar,
 				mathtype=spux.MathType.Integer,
 				abs_min=1,
 				default_value=3,
 			),
 			'α Range': sockets.ExprSocketDef(
-				shape=(2,),
+				size=spux.NumberSize1D.Vec2,
 				mathtype=spux.MathType.Real,
 				default_value=sp.Matrix([0, 1.5]),
 				abs_min=0,

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/inputs/constants/physical_constant.py

@@ -59,7 +59,6 @@ class PhysicalConstantNode(base.MaxwellSimNode):
 
 	size: spux.NumberSize1D = bl_cache.BLField(
 		enum_cb=lambda self, _: self.search_sizes(),
-		prop_ui=True,
 	)
 
 	####################
@@ -75,7 +74,7 @@ class PhysicalConstantNode(base.MaxwellSimNode):
 		return [
 			spux.NumberSize1D.from_shape(shape).bl_enum_element(i)
 			for i, shape in enumerate(self.physical_type.valid_shapes)
-			if spux.NumberSize1D.supports_shape(shape)
+			if spux.NumberSize1D.has_shape(shape)
 		]
 
 	####################

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/inputs/scene.py

@@ -16,11 +16,11 @@
 
 """Implements `SceneNode`."""
 
-import enum
 import typing as typ
 
 import bpy
 import sympy as sp
+import sympy.physics.units as spu
 
 from blender_maxwell.utils import bl_cache, logger
 from blender_maxwell.utils import extra_sympy_units as spux
@@ -45,7 +45,11 @@ class SceneNode(base.MaxwellSimNode):
 	input_sockets: typ.ClassVar = {
 		'Frames / Unit': sockets.ExprSocketDef(
 			mathtype=spux.MathType.Integer,
-			default_value=24,
+			default_value=48,
+		),
+		'Unit': sockets.ExprSocketDef(
+			default_unit=spu.ps,
+			default_value=1,
 		),
 	}
 	output_sockets: typ.ClassVar = {
@@ -60,7 +64,7 @@ class SceneNode(base.MaxwellSimNode):
 	####################
 	# - Properties: Frame
 	####################
-	@property
+	@bl_cache.cached_bl_property()
 	def scene_frame(self) -> int:
 		"""Retrieve the current frame of the scene.
 
@@ -71,6 +75,7 @@ class SceneNode(base.MaxwellSimNode):
 
 	@property
 	def scene_frame_range(self) -> ct.LazyArrayRangeFlow:
+		"""Retrieve the current start/end frame of the scene, with `steps` corresponding to single-frame steps."""
 		frame_start = bpy.context.scene.frame_start
 		frame_stop = bpy.context.scene.frame_end
 		return ct.LazyArrayRangeFlow(
@@ -79,69 +84,20 @@ class SceneNode(base.MaxwellSimNode):
 			steps=frame_stop - frame_start + 1,
 		)
 
-	####################
-	# - Property: Time Unit
-	####################
-	active_time_unit: enum.Enum = bl_cache.BLField(
-		enum_cb=lambda self, _: self.search_units(), prop_ui=True
-	)
-
-	def search_units(self) -> list[ct.BLEnumElement]:
-		return [
-			(sp.sstr(unit), spux.sp_to_str(unit), sp.sstr(unit), '', i)
-			for i, unit in enumerate(spux.PhysicalType.Time.valid_units)
-		]
-
-	@property
-	def time_unit(self) -> spux.Unit | None:
-		"""Gets the current active unit.
-
-		Returns:
-			The current active `sympy` unit.
-
-			If the socket expression is unitless, this returns `None`.
-		"""
-		if self.active_time_unit is not None:
-			return spux.unit_str_to_unit(self.active_time_unit)
-
-		return None
-
-	@time_unit.setter
-	def time_unit(self, time_unit: spux.Unit | None) -> None:
-		"""Set the unit, without touching the `raw_*` UI properties.
-
-		Notes:
-			To set a new unit, **and** convert the `raw_*` UI properties to the new unit, use `self.convert_unit()` instead.
-		"""
-		if time_unit in spux.PhysicalType.Time.valid_units:
-			self.active_time_unit = sp.sstr(time_unit)
-		else:
-			msg = f'Tried to set invalid time unit {time_unit}'
-			raise ValueError(msg)
-
-	####################
-	# - UI
-	####################
-	def draw_props(self, _: bpy.types.Context, col: bpy.types.UILayout) -> None:
-		"""Draws the button that allows toggling between single and range output.
-
-		Parameters:
-			col: Target for defining UI elements.
-		"""
-		col.prop(self, self.blfields['active_time_unit'], toggle=True, text='Unit')
-
 	####################
 	# - FlowKinds
 	####################
 	@events.computes_output_socket(
 		'Time',
 		kind=ct.FlowKind.Value,
-		input_sockets={'Frames / Unit'},
-		props={'scene_frame', 'active_time_unit', 'time_unit'},
+		input_sockets={'Frames / Unit', 'Unit'},
+		props={'scene_frame'},
 	)
 	def compute_time(self, props, input_sockets) -> sp.Expr:
 		return (
-			props['scene_frame'] / input_sockets['Frames / Unit'] * props['time_unit']
+			props['scene_frame']
+			/ input_sockets['Frames / Unit']
+			* input_sockets['Unit']
 		)
 
 	@events.computes_output_socket(
@@ -159,10 +115,18 @@ class SceneNode(base.MaxwellSimNode):
 BL_REGISTER = [
 	SceneNode,
 ]
+BL_NODES = {ct.NodeType.Scene: (ct.NodeCategory.MAXWELLSIM_INPUTS)}
 
 
+####################
+# - Blender Handlers
+####################
 @bpy.app.handlers.persistent
-def update_scene_node_after_frame_changed(scene, depsgraph) -> None:
+def update_scene_node_after_frame_changed(
+	scene: bpy.types.Scene,  # noqa: ARG001
+	depsgraph: bpy.types.Depsgraph,  # noqa: ARG001
+) -> None:
+	"""Invalidate the cached scene frame on all `SceneNode`s in all active simulation node trees, whenever the frame changes."""
 	for node_tree in [
 		_node_tree
 		for _node_tree in bpy.data.node_groups
@@ -173,9 +137,7 @@ def update_scene_node_after_frame_changed(scene, depsgraph) -> None:
 			for _node in node_tree.nodes
 			if hasattr(_node, 'node_type') and _node.node_type == ct.NodeType.Scene
 		]:
-			node.trigger_event(ct.FlowEvent.DataChanged, prop_name='scene_frame')
+			node.scene_frame = bl_cache.Signal.InvalidateCache
 
 
 bpy.app.handlers.frame_change_post.append(update_scene_node_after_frame_changed)
-
-BL_NODES = {ct.NodeType.Scene: (ct.NodeCategory.MAXWELLSIM_INPUTS)}

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/inputs/wave_constant.py

@@ -49,36 +49,28 @@ class WaveConstantNode(base.MaxwellSimNode):
 	input_socket_sets: typ.ClassVar = {
 		'Wavelength': {
 			'WL': sockets.ExprSocketDef(
-				active_kind=ct.FlowKind.Value,
-				physical_type=spux.PhysicalType.Length,
-				# Defaults
 				default_unit=spu.nm,
 				default_value=500,
 				default_min=200,
 				default_max=700,
-				default_steps=2,
+				default_steps=50,
 			)
 		},
 		'Frequency': {
 			'Freq': sockets.ExprSocketDef(
-				active_kind=ct.FlowKind.Value,
-				physical_type=spux.PhysicalType.Freq,
-				# Defaults
 				default_unit=spux.THz,
 				default_value=1,
 				default_min=0.3,
 				default_max=3,
-				default_steps=2,
+				default_steps=50,
 			),
 		},
 	}
 	output_sockets: typ.ClassVar = {
 		'WL': sockets.ExprSocketDef(
-			active_kind=ct.FlowKind.Value,
 			physical_type=spux.PhysicalType.Length,
 		),
 		'Freq': sockets.ExprSocketDef(
-			active_kind=ct.FlowKind.Value,
 			physical_type=spux.PhysicalType.Freq,
 		),
 	}
@@ -86,7 +78,7 @@ class WaveConstantNode(base.MaxwellSimNode):
 	####################
 	# - Properties
 	####################
-	use_range: bool = bl_cache.BLField(False, prop_ui=True)
+	use_range: bool = bl_cache.BLField(False)
 
 	####################
 	# - UI
@@ -192,6 +184,7 @@ class WaveConstantNode(base.MaxwellSimNode):
 				sci_constants.vac_speed_of_light / (freq.start * freq.unit), spu.um
 			),
 			steps=freq.steps,
+			scaling=freq.scaling,
 			unit=spu.um,
 		)
 
@@ -220,6 +213,7 @@ class WaveConstantNode(base.MaxwellSimNode):
 				sci_constants.vac_speed_of_light / (wl.start * wl.unit), spux.THz
 			),
 			steps=wl.steps,
+			scaling=wl.scaling,
 			unit=spux.THz,
 		)
 

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/mediums/library_medium.py

@@ -109,11 +109,7 @@ class LibraryMediumNode(base.MaxwellSimNode):
 	####################
 	# - Sockets
 	####################
-	input_sockets: typ.ClassVar = {
-		'Generated Steps': sockets.ExprSocketDef(
-			mathtype=spux.MathType.Integer, default_value=2, abs_min=2
-		)
-	}
+	input_sockets: typ.ClassVar = {}
 	output_sockets: typ.ClassVar = {
 		'Medium': sockets.MaxwellMediumSocketDef(),
 		'Valid Freqs': sockets.ExprSocketDef(
@@ -133,9 +129,9 @@ class LibraryMediumNode(base.MaxwellSimNode):
 	####################
 	# - Properties
 	####################
-	vendored_medium: VendoredMedium = bl_cache.BLField(VendoredMedium.Au, prop_ui=True)
-	variant_name: enum.Enum = bl_cache.BLField(
-		prop_ui=True, enum_cb=lambda self, _: self.search_variants()
+	vendored_medium: VendoredMedium = bl_cache.BLField(VendoredMedium.Au)
+	variant_name: enum.StrEnum = bl_cache.BLField(
+		enum_cb=lambda self, _: self.search_variants()
 	)
 
 	def search_variants(self) -> list[ct.BLEnumElement]:
@@ -145,28 +141,28 @@ class LibraryMediumNode(base.MaxwellSimNode):
 	####################
 	# - Computed
 	####################
-	@property
+	@bl_cache.cached_bl_property(depends_on={'vendored_medium', 'variant_name'})
 	def variant(self) -> Tidy3DMediumVariant:
 		"""Deduce the actual medium variant from `self.vendored_medium` and `self.variant_name`."""
 		return self.vendored_medium.medium_variants[self.variant_name]
 
-	@property
+	@bl_cache.cached_bl_property(depends_on={'variant'})
 	def medium(self) -> td.PoleResidue:
 		"""Deduce the actual currently selected `PoleResidue` medium from `self.variant`."""
 		return self.variant.medium
 
-	@property
+	@bl_cache.cached_bl_property(depends_on={'variant'})
 	def data_url(self) -> str | None:
 		"""Deduce the URL associated with the currently selected medium from `self.variant`."""
 		return self.variant.data_url
 
-	@property
+	@bl_cache.cached_bl_property(depends_on={'variant'})
 	def references(self) -> td.PoleResidue:
 		"""Deduce the references associated with the currently selected `PoleResidue` medium from `self.variant`."""
 		return self.variant.reference
 
-	@property
-	def freq_range(self) -> spux.SympyExpr:
+	@bl_cache.cached_bl_property(depends_on={'medium'})
+	def freq_range(self) -> sp.Expr:
 		"""Deduce the frequency range as a unit-aware (THz, for convenience) column vector.
 
 		A rational approximation to each frequency bound is computed with `sp.nsimplify`, in order to **guarantee** lack of precision-loss as computations are performed on the frequency.
@@ -178,8 +174,8 @@ class LibraryMediumNode(base.MaxwellSimNode):
 			spux.terahertz,
 		)
 
-	@property
-	def wl_range(self) -> spux.SympyExpr:
+	@bl_cache.cached_bl_property(depends_on={'freq_range'})
+	def wl_range(self) -> sp.Expr:
 		"""Deduce the vacuum wavelength range as a unit-aware (nanometer, for convenience) column vector."""
 		return sp.Matrix(
 			self.freq_range.applyfunc(
@@ -203,12 +199,12 @@ class LibraryMediumNode(base.MaxwellSimNode):
 			formatted_str = f'{number:.2e}'
 		return formatted_str
 
-	@bl_cache.cached_bl_property()
+	@bl_cache.cached_bl_property(depends_on={'freq_range'})
 	def ui_freq_range(self) -> tuple[str, str]:
 		"""Cached mirror of `self.wl_range` which contains UI-ready strings."""
 		return tuple([self._ui_range_format(el) for el in self.freq_range])
 
-	@bl_cache.cached_bl_property()
+	@bl_cache.cached_bl_property(depends_on={'wl_range'})
 	def ui_wl_range(self) -> tuple[str, str]:
 		"""Cached mirror of `self.wl_range` which contains UI-ready strings."""
 		return tuple([self._ui_range_format(el) for el in self.wl_range])
@@ -279,14 +275,13 @@ class LibraryMediumNode(base.MaxwellSimNode):
 		'Valid Freqs',
 		kind=ct.FlowKind.LazyArrayRange,
 		props={'freq_range'},
-		input_sockets={'Generated Steps'},
 	)
-	def compute_valid_freqs_lazy(self, props, input_sockets) -> sp.Expr:
+	def compute_valid_freqs_lazy(self, props) -> sp.Expr:
 		return ct.LazyArrayRangeFlow(
 			start=props['freq_range'][0] / spux.THz,
 			stop=props['freq_range'][1] / spux.THz,
-			steps=input_sockets['Generated Steps'],
-			scaling='lin',
+			steps=0,
+			scaling=ct.ScalingMode.Lin,
 			unit=spux.THz,
 		)
 
@@ -301,14 +296,13 @@ class LibraryMediumNode(base.MaxwellSimNode):
 		'Valid WLs',
 		kind=ct.FlowKind.LazyArrayRange,
 		props={'wl_range'},
-		input_sockets={'Generated Steps'},
 	)
-	def compute_valid_wls_lazy(self, props, input_sockets) -> sp.Expr:
+	def compute_valid_wls_lazy(self, props) -> sp.Expr:
 		return ct.LazyArrayRangeFlow(
 			start=props['wl_range'][0] / spu.nm,
 			stop=props['wl_range'][0] / spu.nm,
-			steps=input_sockets['Generated Steps'],
-			scaling='lin',
+			steps=0,
+			scaling=ct.ScalingMode.Lin,
 			unit=spu.nm,
 		)
 

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/monitors/eh_field_monitor.py

@@ -43,16 +43,16 @@ class EHFieldMonitorNode(base.MaxwellSimNode):
 	####################
 	input_sockets: typ.ClassVar = {
 		'Center': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			physical_type=spux.PhysicalType.Length,
 		),
 		'Size': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			physical_type=spux.PhysicalType.Length,
 			default_value=sp.Matrix([1, 1, 1]),
 		),
 		'Spatial Subdivs': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			mathtype=spux.MathType.Integer,
 			default_value=sp.Matrix([10, 10, 10]),
 		),

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/monitors/field_power_flux_monitor.py

@@ -41,16 +41,16 @@ class PowerFluxMonitorNode(base.MaxwellSimNode):
 	####################
 	input_sockets: typ.ClassVar = {
 		'Center': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			physical_type=spux.PhysicalType.Length,
 		),
 		'Size': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			physical_type=spux.PhysicalType.Length,
 			default_value=sp.Matrix([1, 1, 1]),
 		),
 		'Samples/Space': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			mathtype=spux.MathType.Integer,
 			default_value=sp.Matrix([10, 10, 10]),
 		),

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/outputs/viewer.py

@@ -19,8 +19,8 @@ import typing as typ
 import bpy
 import sympy as sp
 
+from blender_maxwell.utils import bl_cache, logger
 from blender_maxwell.utils import extra_sympy_units as spux
-from blender_maxwell.utils import logger
 
 from ... import contracts as ct
 from ... import sockets
@@ -73,33 +73,15 @@ class ViewerNode(base.MaxwellSimNode):
 	####################
 	# - Properties
 	####################
-	print_kind: bpy.props.EnumProperty(
-		name='Print Kind',
-		description='FlowKind of the input socket to print',
-		items=[(kind, kind.name, kind.name) for kind in list(ct.FlowKind)],
-		default=ct.FlowKind.Value,
-		update=lambda self, context: self.on_prop_changed('print_kind', context),
-	)
-
-	auto_plot: bpy.props.BoolProperty(
-		name='Auto-Plot',
-		description='Whether to auto-plot anything plugged into the viewer node',
-		default=False,
-		update=lambda self, context: self.on_prop_changed('auto_plot', context),
-	)
-
-	auto_3d_preview: bpy.props.BoolProperty(
-		name='Auto 3D Preview',
-		description="Whether to auto-preview anything 3D, that's plugged into the viewer node",
-		default=True,
-		update=lambda self, context: self.on_prop_changed('auto_3d_preview', context),
-	)
+	print_kind: ct.FlowKind = bl_cache.BLField(ct.FlowKind.Value)
+	auto_plot: bool = bl_cache.BLField(False)
+	auto_3d_preview: bool = bl_cache.BLField(True)
 
 	####################
 	# - UI
 	####################
 	def draw_props(self, _: bpy.types.Context, layout: bpy.types.UILayout):
-		layout.prop(self, 'print_kind', text='')
+		layout.prop(self, self.blfields['print_kind'], text='')
 
 	def draw_operators(self, _: bpy.types.Context, layout: bpy.types.UILayout):
 		split = layout.split(factor=0.4)
@@ -118,7 +100,7 @@ class ViewerNode(base.MaxwellSimNode):
 
 		## Plot Options
 		row = col.row(align=True)
-		row.prop(self, 'auto_plot', text='Plot', toggle=True)
+		row.prop(self, self.blfields['auto_plot'], text='Plot', toggle=True)
 		row.operator(
 			RefreshPlotViewOperator.bl_idname,
 			text='',
@@ -127,7 +109,7 @@ class ViewerNode(base.MaxwellSimNode):
 
 		## 3D Preview Options
 		row = col.row(align=True)
-		row.prop(self, 'auto_3d_preview', text='3D Preview', toggle=True)
+		row.prop(self, self.blfields['auto_3d_preview'], text='3D Preview', toggle=True)
 
 	####################
 	# - Methods

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/outputs/web_exporters/tidy3d_web_exporter.py

@@ -144,7 +144,7 @@ class Tidy3DWebExporterNode(base.MaxwellSimNode):
 	####################
 	# - Computed - Sim
 	####################
-	@bl_cache.cached_bl_property(persist=False)
+	@bl_cache.cached_bl_property()
 	def sim(self) -> td.Simulation | None:
 		sim = self._compute_input('Sim')
 		has_sim = not ct.FlowSignal.check(sim)
@@ -153,7 +153,7 @@ class Tidy3DWebExporterNode(base.MaxwellSimNode):
 			return sim
 		return None
 
-	@bl_cache.cached_bl_property(persist=False)
+	@bl_cache.cached_bl_property()
 	def total_monitor_data(self) -> float | None:
 		if self.sim is not None:
 			return sum(self.sim.monitors_data_size.values())
@@ -188,8 +188,9 @@ class Tidy3DWebExporterNode(base.MaxwellSimNode):
 		If one can't be loaded, return None.
 		"""
 		has_uploaded_task = self.uploaded_task_id != ''
+		has_new_cloud_task = self.new_cloud_task is not None
 
-		if has_uploaded_task:
+		if has_uploaded_task and has_new_cloud_task:
 			return tdcloud.TidyCloudTasks.tasks(self.new_cloud_task.cloud_folder).get(
 				self.uploaded_task_id
 			)
@@ -206,7 +207,7 @@ class Tidy3DWebExporterNode(base.MaxwellSimNode):
 			return tdcloud.TidyCloudTasks.task_info(self.uploaded_task_id)
 		return None
 
-	@bl_cache.cached_bl_property(persist=False)
+	@bl_cache.cached_bl_property()
 	def uploaded_est_cost(self) -> float | None:
 		task_info = self.uploaded_task_info
 		if task_info is not None:
@@ -219,7 +220,7 @@ class Tidy3DWebExporterNode(base.MaxwellSimNode):
 	####################
 	# - Computed - Combined
 	####################
-	@bl_cache.cached_bl_property(persist=False)
+	@bl_cache.cached_bl_property()
 	def is_sim_uploadable(self) -> bool:
 		if (
 			self.sim is not None

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/simulations/sim_domain.py

@@ -43,14 +43,14 @@ class SimDomainNode(base.MaxwellSimNode):
 			abs_min=0,
 		),
 		'Center': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			mathtype=spux.MathType.Real,
 			physical_type=spux.PhysicalType.Length,
 			default_unit=spu.micrometer,
 			default_value=sp.Matrix([0, 0, 0]),
 		),
 		'Size': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			mathtype=spux.MathType.Real,
 			physical_type=spux.PhysicalType.Length,
 			default_unit=spu.micrometer,

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/sources/gaussian_beam_source.py

@@ -54,13 +54,13 @@ class GaussianBeamSourceNode(base.MaxwellSimNode):
 	input_sockets: typ.ClassVar = {
 		'Temporal Shape': sockets.MaxwellTemporalShapeSocketDef(),
 		'Center': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			mathtype=spux.MathType.Real,
 			physical_type=spux.PhysicalType.Length,
 			default_value=sp.Matrix([0, 0, 0]),
 		),
 		'Size': sockets.ExprSocketDef(
-			shape=(2,),
+			size=spux.NumberSize1D.Vec2,
 			mathtype=spux.MathType.Real,
 			physical_type=spux.PhysicalType.Length,
 			default_value=sp.Matrix([1, 1]),
@@ -77,7 +77,7 @@ class GaussianBeamSourceNode(base.MaxwellSimNode):
 			abs_min=0.01,
 		),
 		'Spherical': sockets.ExprSocketDef(
-			shape=(2,),
+			size=spux.NumberSize1D.Vec2,
 			mathtype=spux.MathType.Real,
 			physical_type=spux.PhysicalType.Angle,
 			default_value=sp.Matrix([0, 0]),

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/sources/plane_wave_source.py

@@ -52,13 +52,13 @@ class PlaneWaveSourceNode(base.MaxwellSimNode):
 	input_sockets: typ.ClassVar = {
 		'Temporal Shape': sockets.MaxwellTemporalShapeSocketDef(),
 		'Center': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			mathtype=spux.MathType.Real,
 			physical_type=spux.PhysicalType.Length,
 			default_value=sp.Matrix([0, 0, 0]),
 		),
 		'Spherical': sockets.ExprSocketDef(
-			shape=(2,),
+			size=spux.NumberSize1D.Vec2,
 			mathtype=spux.MathType.Real,
 			physical_type=spux.PhysicalType.Angle,
 			default_value=sp.Matrix([0, 0]),

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/sources/point_dipole_source.py

@@ -42,7 +42,7 @@ class PointDipoleSourceNode(base.MaxwellSimNode):
 	input_sockets: typ.ClassVar = {
 		'Temporal Shape': sockets.MaxwellTemporalShapeSocketDef(),
 		'Center': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			mathtype=spux.MathType.Real,
 			physical_type=spux.PhysicalType.Length,
 			default_value=sp.Matrix([0, 0, 0]),

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/structures/geonodes_structure.py

@@ -42,7 +42,7 @@ class GeoNodesStructureNode(base.MaxwellSimNode):
 		'GeoNodes': sockets.BlenderGeoNodesSocketDef(),
 		'Medium': sockets.MaxwellMediumSocketDef(),
 		'Center': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			mathtype=spux.MathType.Real,
 			physical_type=spux.PhysicalType.Length,
 			default_unit=spu.micrometer,

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/structures/primitives/box_structure.py

@@ -42,14 +42,14 @@ class BoxStructureNode(base.MaxwellSimNode):
 	input_sockets: typ.ClassVar = {
 		'Medium': sockets.MaxwellMediumSocketDef(),
 		'Center': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			mathtype=spux.MathType.Real,
 			physical_type=spux.PhysicalType.Length,
 			default_unit=spu.micrometer,
 			default_value=sp.Matrix([0, 0, 0]),
 		),
 		'Size': sockets.ExprSocketDef(
-			shape=(3,),
+			size=spux.NumberSize1D.Vec3,
 			mathtype=spux.MathType.Real,
 			physical_type=spux.PhysicalType.Length,
 			default_unit=spu.nanometer,

src/blender_maxwell/node_trees/maxwell_sim_nodes/nodes/structures/primitives/sphere_structure.py

@@ -42,14 +42,11 @@ class SphereStructureNode(base.MaxwellSimNode):
 	input_sockets: typ.ClassVar = {
 		'Medium': sockets.MaxwellMediumSocketDef(),
 		'Center': sockets.ExprSocketDef(
-			shape=(3,),
-			mathtype=spux.MathType.Real,
-			physical_type=spux.PhysicalType.Length,
+			size=spux.NumberSize1D.Vec3,
 			default_unit=spu.micrometer,
 			default_value=sp.Matrix([0, 0, 0]),
 		),
 		'Radius': sockets.ExprSocketDef(
-			physical_type=spux.PhysicalType.Length,
 			default_unit=spu.nanometer,
 			default_value=150,
 		),

src/blender_maxwell/node_trees/maxwell_sim_nodes/sockets/base.py

@@ -16,13 +16,11 @@
 
 import abc
 import typing as typ
-import uuid
-from types import MappingProxyType
 
 import bpy
 import pydantic as pyd
 
-from blender_maxwell.utils import bl_cache, logger, serialize
+from blender_maxwell.utils import bl_cache, bl_instance, logger, serialize
 
 from .. import contracts as ct
 
@@ -60,7 +58,7 @@ class SocketDef(pyd.BaseModel, abc.ABC):
 		Parameters:
 			bl_socket: The Blender node socket to alter using data from this SocketDef.
 		"""
-		bl_socket.initializing = False
+		bl_socket.is_initializing = False
 		bl_socket.on_active_kind_changed()
 
 	@abc.abstractmethod
@@ -116,9 +114,12 @@ class SocketDef(pyd.BaseModel, abc.ABC):
 
 
 ####################
-# - SocketDef
+# - Socket
 ####################
-class MaxwellSimSocket(bpy.types.NodeSocket):
+MANDATORY_PROPS: set[str] = {'socket_type', 'bl_label'}
+
+
+class MaxwellSimSocket(bpy.types.NodeSocket, bl_instance.BLInstance):
 	"""A specialized Blender socket for nodes in a Maxwell simulation.
 
 	Attributes:
@@ -128,112 +129,45 @@ class MaxwellSimSocket(bpy.types.NodeSocket):
 		locked: The lock-state of a particular socket, which determines the socket's user editability
 	"""
 
-	# Fundamentals
+	# Properties
+	## Class
 	socket_type: ct.SocketType
 	bl_label: str
 
-	# Style
-	display_shape: typ.Literal[
-		'CIRCLE',
-		'SQUARE',
-		'DIAMOND',
-		'CIRCLE_DOT',
-		'SQUARE_DOT',
-		'DIAMOND_DOT',
-	]
-	## We use the following conventions for shapes:
-	## - CIRCLE: Single Value.
-	## - SQUARE: Container of Value.
-	## - DIAMOND: Pointer Value.
-	## - +DOT: Uses Units
-	socket_color: tuple
-
-	# Options
-	use_prelock: bool = False
-	use_info_draw: bool = False
-
-	# Computed
+	## Computed by Subclass
 	bl_idname: str
 
 	# BLFields
-	blfields: typ.ClassVar[dict[str, str]] = MappingProxyType({})
-	ui_blfields: typ.ClassVar[set[str]] = frozenset()
+	## Identifying
+	is_initializing: bool = bl_cache.BLField(True, use_prop_update=False)
+
+	active_kind: ct.FlowKind = bl_cache.BLField(ct.FlowKind.Value)
+
+	## UI
+	use_info_draw: bool = bl_cache.BLField(False, use_prop_update=False)
+	use_prelock: bool = bl_cache.BLField(False, use_prop_update=False)
+
+	locked: bool = bl_cache.BLField(False, use_prop_update=False)
+
+	use_socket_color: bool = bl_cache.BLField(False, use_prop_update=False)
+	socket_color: tuple[float, float, float, float] = bl_cache.BLField(
+		(0, 0, 0, 0), use_prop_update=False
+	)
 
 	####################
 	# - Initialization
 	####################
-	## TODO: Common implementation of this for both sockets and nodes - perhaps a BLInstance base class?
-	def reset_instance_id(self) -> None:
-		self.instance_id = str(uuid.uuid4())
-
-	@classmethod
-	def declare_blfield(
-		cls, attr_name: str, bl_attr_name: str, prop_ui: bool = False
-	) -> None:
-		cls.blfields = cls.blfields | {attr_name: bl_attr_name}
-
-		if prop_ui:
-			cls.ui_blfields = cls.ui_blfields | {attr_name}
-
-	@classmethod
-	def set_prop(
-		cls,
-		prop_name: str,
-		prop: bpy.types.Property,
-		no_update: bool = False,
-		update_with_name: str | None = None,
-		**kwargs,
-	) -> None:
-		"""Adds a Blender property to a class via `__annotations__`, so it initializes with any subclass.
+	def __init_subclass__(cls, **kwargs: typ.Any):
+		"""Initializes socket properties and attributes for use.
 
 		Notes:
-			- Blender properties can't be set within `__init_subclass__` simply by adding attributes to the class; they must be added as type annotations.
-			- Must be called **within** `__init_subclass__`.
-
-		Parameters:
-			name: The name of the property to set.
-			prop: The `bpy.types.Property` to instantiate and attach..
-			no_update: Don't attach a `self.on_prop_changed()` callback to the property's `update`.
+			Run when initializing any subclass of MaxwellSimSocket.
 		"""
-		_update_with_name = prop_name if update_with_name is None else update_with_name
-		extra_kwargs = (
-			{
-				'update': lambda self, context: self.on_prop_changed(
-					_update_with_name, context
-				),
-			}
-			if not no_update
-			else {}
-		)
-		cls.__annotations__[prop_name] = prop(
-			**kwargs,
-			**extra_kwargs,
-		)
-
-	def __init_subclass__(cls, **kwargs: typ.Any):
 		log.debug('Initializing Socket: %s', cls.socket_type)
 		super().__init_subclass__(**kwargs)
-		# cls._assert_attrs_valid()
-		## TODO: Implement this :)
+		cls.assert_attrs_valid(MANDATORY_PROPS)
 
-		# Socket Properties
-		## Identifiers
 		cls.bl_idname: str = str(cls.socket_type.value)
-		cls.set_prop('instance_id', bpy.props.StringProperty, no_update=True)
-		cls.set_prop(
-			'initializing', bpy.props.BoolProperty, default=True, no_update=True
-		)
-
-		## Special States
-		cls.set_prop('locked', bpy.props.BoolProperty, no_update=True, default=False)
-
-		# Setup Style
-		cls.socket_color = ct.SOCKET_COLORS[cls.socket_type]
-
-		# Setup List
-		cls.set_prop(
-			'active_kind', bpy.props.StringProperty, default=str(ct.FlowKind.Value)
-		)
 
 	####################
 	# - Property Event: On Update
@@ -244,12 +178,7 @@ class MaxwellSimSocket(bpy.types.NodeSocket):
 		Notes:
 			Called by `self.on_prop_changed()` when `self.active_kind` was changed.
 		"""
-		self.display_shape = {
-			ct.FlowKind.Value: 'CIRCLE',
-			ct.FlowKind.Array: 'SQUARE',
-			ct.FlowKind.LazyArrayRange: 'SQUARE',
-			ct.FlowKind.LazyValueFunc: 'DIAMOND',
-		}[self.active_kind]
+		self.display_shape = self.active_kind.socket_shape
 
 	def on_socket_prop_changed(self, prop_name: str) -> None:
 		"""Called when a property has been updated.
@@ -264,7 +193,7 @@ class MaxwellSimSocket(bpy.types.NodeSocket):
 			prop_name: The name of the property that was changed.
 		"""
 
-	def on_prop_changed(self, prop_name: str, _: bpy.types.Context) -> None:
+	def on_prop_changed(self, prop_name: str) -> None:
 		"""Called when a property has been updated.
 
 		Contrary to `node.on_prop_changed()`, socket-specific callbacks are baked into this function:
@@ -275,17 +204,13 @@ class MaxwellSimSocket(bpy.types.NodeSocket):
 			prop_name: The name of the property that was changed.
 		"""
 		## TODO: Evaluate this properly
-		if self.initializing:
+		if self.is_initializing:
 			log.debug(
 				'%s: Rejected on_prop_changed("%s") while initializing',
 				self.bl_label,
 				prop_name,
 			)
 		elif hasattr(self, prop_name):
-			# Invalidate UI BLField Caches
-			if prop_name in self.ui_blfields:
-				setattr(self, prop_name, bl_cache.Signal.InvalidateCache)
-
 			# Property Callbacks: Active Kind
 			if prop_name == 'active_kind':
 				self.on_active_kind_changed()
@@ -469,13 +394,13 @@ class MaxwellSimSocket(bpy.types.NodeSocket):
 		if event in [ct.FlowEvent.EnableLock, ct.FlowEvent.DisableLock]:
 			self.locked = event == ct.FlowEvent.EnableLock
 
-		# Input Socket | Input Flow
-		if not self.is_output and flow_direction == 'input':
+		# Event by Socket Orientation | Flow Direction
+		match (self.is_output, flow_direction):
+			case (False, 'input'):
 				for link in self.links:
 					link.from_socket.trigger_event(event, socket_kinds=socket_kinds)
 
-		# Input Socket | Output Flow
-		if not self.is_output and flow_direction == 'output':
+			case (False, 'output'):
 				if event == ct.FlowEvent.LinkChanged:
 					self.node.trigger_event(
 						ct.FlowEvent.DataChanged,
@@ -487,14 +412,12 @@ class MaxwellSimSocket(bpy.types.NodeSocket):
 						event, socket_name=self.name, socket_kinds=socket_kinds
 					)
 
-		# Output Socket | Input Flow
-		if self.is_output and flow_direction == 'input':
+			case (True, 'input'):
 				self.node.trigger_event(
 					event, socket_name=self.name, socket_kinds=socket_kinds
 				)
 
-		# Output Socket | Output Flow
-		if self.is_output and flow_direction == 'output':
+			case (True, 'output'):
 				for link in self.links:
 					link.to_socket.trigger_event(event, socket_kinds=socket_kinds)
 
@@ -729,19 +652,24 @@ class MaxwellSimSocket(bpy.types.NodeSocket):
 		raise NotImplementedError(msg)
 
 	####################
-	# - Theme
+	# - UI - Color
 	####################
-	@classmethod
-	def draw_color_simple(cls) -> ct.BLColorRGBA:
-		"""Sets the socket's color to `cls.socket_color`.
+	def draw_color(
+		self,
+		_: bpy.types.Context,
+		node: bpy.types.Node,  # noqa: ARG002
+	) -> tuple[float, float, float, float]:
+		"""Draw the socket color depending on context.
+
+		When `self.use_socket_color` is set, the property `socket_color` can be used to control the socket color directly.
+		Otherwise, a default based on `self.socket_type` will be used.
 
 		Notes:
-			Blender calls this method to determine the socket color.
-
-		Returns:
-			A Blender-compatible RGBA value, with no explicit color space.
+			Called by Blender to call the socket color.
 		"""
-		return cls.socket_color
+		if self.use_socket_color:
+			return self.socket_color
+		return ct.SOCKET_COLORS[self.socket_type]
 
 	####################
 	# - UI

src/blender_maxwell/node_trees/maxwell_sim_nodes/sockets/basic/file_path.py

@@ -18,9 +18,13 @@ from pathlib import Path
 
 import bpy
 
+from blender_maxwell.utils import bl_cache, logger
+
 from ... import contracts as ct
 from .. import base
 
+log = logger.get(__name__)
+
 
 ####################
 # - Blender Socket
@@ -32,30 +36,25 @@ class FilePathBLSocket(base.MaxwellSimSocket):
 	####################
 	# - Properties
 	####################
-	raw_value: bpy.props.StringProperty(
-		name='File Path',
-		description='Represents the path to a file',
-		subtype='FILE_PATH',
-		update=(lambda self, context: self.on_prop_changed('raw_value', context)),
-	)
+	raw_value: Path = bl_cache.BLField(Path(), path_type='file')
 
 	####################
 	# - Socket UI
 	####################
 	def draw_value(self, col: bpy.types.UILayout) -> None:
-		col_row = col.row(align=True)
-		col_row.prop(self, 'raw_value', text='')
+		# col_row = col.row(align=True)
+		col.prop(self, self.blfields['raw_value'], text='')
 
 	####################
-	# - Computation of Default Value
+	# - FlowKind: Value
 	####################
 	@property
 	def value(self) -> Path:
-		return Path(bpy.path.abspath(self.raw_value))
+		return self.raw_value
 
 	@value.setter
 	def value(self, value: Path) -> None:
-		self.raw_value = bpy.path.relpath(str(value))
+		self.raw_value = value
 
 
 ####################

src/blender_maxwell/node_trees/maxwell_sim_nodes/sockets/tidy3d/cloud_task.py

@@ -99,18 +99,16 @@ class Tidy3DCloudTaskBLSocket(base.MaxwellSimSocket):
 	socket_type = ct.SocketType.Tidy3DCloudTask
 	bl_label = 'Tidy3D Cloud Task'
 
-	use_prelock = True
-
 	####################
 	# - Properties
 	####################
 	api_key: str = bl_cache.BLField('', prop_ui=True, str_secret=True)
 	should_exist: bool = bl_cache.BLField(False)
 
-	existing_folder_id: enum.Enum = bl_cache.BLField(
+	existing_folder_id: enum.StrEnum = bl_cache.BLField(
 		prop_ui=True, enum_cb=lambda self, _: self.search_cloud_folders()
 	)
-	existing_task_id: enum.Enum = bl_cache.BLField(
+	existing_task_id: enum.StrEnum = bl_cache.BLField(
 		prop_ui=True, enum_cb=lambda self, _: self.search_cloud_tasks()
 	)
 
@@ -299,6 +297,7 @@ class Tidy3DCloudTaskSocketDef(base.SocketDef):
 
 	def init(self, bl_socket: Tidy3DCloudTaskBLSocket) -> None:
 		bl_socket.should_exist = self.should_exist
+		bl_socket.use_prelock = True
 
 
 ####################

src/blender_maxwell/utils/bl_cache/__init__.py

@@ -0,0 +1,36 @@
+# blender_maxwell
+# Copyright (C) 2024 blender_maxwell Project Contributors
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Package providing various tools to handle cached data on Blender objects, especially nodes and node socket classes."""
+
+from .bl_field import BLField
+from .bl_prop import BLProp, BLPropType
+from .cached_bl_property import CachedBLProperty, cached_bl_property
+from .keyed_cache import KeyedCache, keyed_cache
+from .managed_cache import invalidate_nonpersist_instance_id
+from .signal import Signal
+
+__all__ = [
+	'BLField',
+	'BLProp',
+	'BLPropType',
+	'CachedBLProperty',
+	'cached_bl_property',
+	'KeyedCache',
+	'keyed_cache',
+	'invalidate_nonpersist_instance_id',
+	'Signal',
+]

src/blender_maxwell/utils/bl_cache/bl_field.py

@@ -0,0 +1,424 @@
+# blender_maxwell
+# Copyright (C) 2024 blender_maxwell Project Contributors
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Implements various key caches on instances of Blender objects, especially nodes and sockets."""
+
+import functools
+import inspect
+import typing as typ
+
+import bpy
+
+from blender_maxwell import contracts as ct
+from blender_maxwell.utils import bl_instance, logger
+
+from .bl_prop import BLProp
+from .bl_prop_type import BLPropType
+from .signal import Signal
+
+log = logger.get(__name__)
+
+
+StringPropSubType: typ.TypeAlias = typ.Literal[
+	'FILE_PATH', 'DIR_PATH', 'FILE_NAME', 'BYTE_STRING', 'PASSWORD', 'NONE'
+]
+
+StrMethod: typ.TypeAlias = typ.Callable[
+	[bl_instance.BLInstance, bpy.types.Context, str], list[tuple[str, str]]
+]
+EnumMethod: typ.TypeAlias = typ.Callable[
+	[bl_instance.BLInstance, bpy.types.Context], list[ct.BLEnumElement]
+]
+
+DEFAULT_ENUM_ITEMS_SINGLE = [('NONE', 'None', 'No items...', '', 0)]
+DEFAULT_ENUM_ITEMS_MANY = [('NONE', 'None', 'No items...', '', 2**0)]
+
+
+@functools.cache
+def default_enum_items(enum_many: bool) -> list[ct.BLEnumElement]:
+	return DEFAULT_ENUM_ITEMS_MANY if enum_many else DEFAULT_ENUM_ITEMS_SINGLE
+
+
+####################
+# - BLField
+####################
+class BLField:
+	"""A descriptor that allows persisting arbitrary types in Blender objects, with cached reads."""
+
+	def __init__(
+		self,
+		default_value: typ.Any = None,
+		use_prop_update: bool = True,
+		## Static
+		prop_ui: bool = False,  ## TODO: Remove
+		abs_min: int | float | None = None,
+		abs_max: int | float | None = None,
+		soft_min: int | float | None = None,
+		soft_max: int | float | None = None,
+		float_step: int | None = None,
+		float_prec: int | None = None,
+		str_secret: bool | None = None,
+		path_type: typ.Literal['dir', 'file'] | None = None,
+		# blptr_type: typ.Any | None = None,  ## A Blender ID type
+		## TODO: Test/Implement
+		## Dynamic
+		str_cb: StrMethod | None = None,
+		enum_cb: EnumMethod | None = None,
+		cb_depends_on: set[str] | None = None,
+	) -> typ.Self:
+		"""Initializes and sets the attribute to a given default value.
+
+		The attribute **must** declare a type annotation, and it **must** match the type of `default_value`.
+
+		Parameters:
+			default_value: The default value to use if the value is read before it's set.
+			use_prop_update: If True, `BLField` will consent to `bl_instance.on_prop_changed(attr_name)` being run whenever the field is changed.
+				UI changes done to the property via Blender **always** trigger `bl_instance.on_bl_prop_changed`; however, the `BLField` decides whether `on_prop_changed` should be run as well.
+				That control is offered through `use_prop_update`.
+			abs_min: Sets the absolute minimum value of the property.
+				Only meaningful for numerical properties.
+			abs_max: Sets the absolute maximum value of the property.
+				Only meaningful for numerical properties.
+			soft_min: Sets a value which will feel like a minimum in the UI, but which can be overridden by setting a value directly.
+				In practice, "scrolling" through values will stop here.
+				Only meaningful for numerical properties.
+			soft_max: Sets a value which will feel like a maximum in the UI, but which can be overridden by setting a value directly.
+				In practice, "scrolling" through values will stop here.
+				Only meaningful for numerical properties.
+			float_step: Sets the interval (/100) of each step when "scrolling" through the values of a float property, aka. the speed.
+				Only meaningful for float-like properties.
+			float_step: Sets the decimal places of precision to display.
+				Only meaningful for float-like properties.
+			str_secret: Marks the string as "secret", which prevents its save-persistance, and causes the UI to display dots instead of characters.
+				**DO NOT** rely on this property for "real" security.
+				_If in doubt, this isn't good enough._
+				Only meaningful for `str` properties.
+			path_type: Makes the path as pointing to a folder or to a file.
+				Only meaningful for `pathlib.Path` properties.
+				**NOTE**: No effort is made to make paths portable between operating systems.
+				Use with care.
+			str_cb: Method used to determine all valid strings, which presents to the user as a fuzzy-style search dropdown.
+				Only meaningful for `str` properties.
+				Results are not persisted, and must therefore re-run when reloading the file.
+				Otherwise, it is cached, but is re-run whenever `Signal.ResetStrSearch` is set.
+			enum_cb: Method used to determine all valid enum elements, which presents to the user as a dropdown.
+				The caveats with dynamic `bpy.props.EnumProperty`s are **absurdly sharp**.
+				Those caveats are entirely mitigated when using this callback, at the cost of manual resets.
+				Is re-run whenever `Signal.ResetEnumItems` is set, and otherwise cached both persistently and non-persistently.
+			cb_depends_on: Declares that `str_cb` / `enum_cb` should be regenerated whenever any of the given property names change.
+				This allows fully automating the invocation of `Signal.ResetEnumItems` / `Signal.ResetStrSearch` in common cases.
+		"""
+		log.debug(
+			'Initializing BLField (default_value=%s, use_prop_update=%s)',
+			str(default_value),
+			str(use_prop_update),
+		)
+
+		self.use_dynamic_enum = enum_cb is not None
+		self.use_str_search = str_cb is not None
+
+		## TODO: Use prop_flags
+		self.prop_info = {
+			'default': default_value,
+			'use_prop_update': use_prop_update,
+			# Int* | Float*: Bounds
+			'min': abs_min,
+			'max': abs_max,
+			'soft_min': soft_min,
+			'soft_max': soft_max,
+			# Float*: UI
+			'step': float_step,
+			'precision': float_prec,
+			# BLPointer: ID Type
+			#'blptr_type': blptr_type,
+			# Str | Path | Enum: Flag Setters
+			'str_secret': str_secret,
+			'path_type': path_type,
+			# Search: Str
+			'str_search': self.use_str_search,
+			'safe_str_cb': lambda _self, context, edit_text: self.safe_str_cb(
+				_self, context, edit_text
+			),
+			# Search: Enum
+			'enum_dynamic': self.use_dynamic_enum,
+			'safe_enum_cb': lambda _self, context: self.safe_enum_cb(_self, context),
+		}
+
+		# BLProp
+		self.bl_prop: BLProp | None = None
+		self.bl_prop_enum_items: BLProp | None = None
+		self.bl_prop_str_search: BLProp | None = None
+
+		self.enum_cb = enum_cb
+		self.str_cb = str_cb
+
+		self.cb_depends_on: set[str] | None = cb_depends_on
+
+		# Update Suppressing
+		self.suppress_update: dict[str, bool] = {}
+
+	####################
+	# - Descriptor Setup
+	####################
+	def __set_name__(self, owner: type[bl_instance.BLInstance], name: str) -> None:
+		"""Sets up this descriptor on the class, preparing it for per-instance use.
+
+		A `BLProp` is constructed using this descriptor's attribute name on `owner`, and the `self.prop_info` previously created during `self.__init__()`.
+		Then, a corresponding / underlying `bpy.types.Property` is initialized on `owner` using `self.bl_prop.init_bl_type(owner)`
+
+		Notes:
+			Run by Python when setting an instance of a "descriptor" class, to an attribute of another class (denoted `owner`).
+			For more, search for "Python descriptor protocol".
+
+		Parameters:
+			owner: The class that contains an attribute assigned to an instance of this descriptor.
+			name: The name of the attribute that an instance of descriptor was assigned to.
+		"""
+		prop_type = inspect.get_annotations(owner).get(name)
+		self.bl_prop = BLProp(
+			name=name,
+			prop_info=self.prop_info,
+			prop_type=prop_type,
+			bl_prop_type=BLPropType.from_type(prop_type),
+		)
+
+		# Initialize Field on BLClass
+		self.bl_prop.init_bl_type(
+			owner,
+			enum_depends_on=self.cb_depends_on,
+			strsearch_depends_on=self.cb_depends_on,
+		)
+
+		# Dynamic Enum: Initialize Persistent Enum Items
+		if self.prop_info['enum_dynamic']:
+			self.bl_prop_enum_items = BLProp(
+				name=self.bl_prop.enum_cache_key,
+				prop_info={'default': [], 'use_prop_update': False},
+				prop_type=list[ct.BLEnumElement],
+				bl_prop_type=BLPropType.Serialized,
+			)
+			self.bl_prop_enum_items.init_bl_type(owner)
+
+		# Searched Str: Initialize Persistent Str List
+		if self.prop_info['str_search']:
+			self.bl_prop_str_search = BLProp(
+				name=self.bl_prop.str_cache_key,
+				prop_info={'default': [], 'use_prop_update': False},
+				prop_type=list[str],
+				bl_prop_type=BLPropType.Serialized,
+			)
+			self.bl_prop_str_search.init_bl_type(owner)
+
+	def __get__(
+		self,
+		bl_instance: bl_instance.BLInstance | None,
+		owner: type[bl_instance.BLInstance],
+	) -> typ.Any:
+		"""Retrieves the value described by the BLField.
+
+		Notes:
+			Run by Python when the attribute described by the descriptor is accessed.
+			For more, search for "Python descriptor protocol".
+
+		Parameters:
+			bl_instance: Instance that is accessing the attribute.
+			owner: The class that owns the instance.
+		"""
+		# Compute Value (if available)
+		cached_value = self.bl_prop.read_nonpersist(bl_instance)
+		if cached_value is Signal.CacheNotReady or cached_value is Signal.CacheEmpty:
+			if bl_instance is not None:
+				persisted_value = self.bl_prop.read(bl_instance)
+				self.bl_prop.write_nonpersist(bl_instance, persisted_value)
+				return persisted_value
+			return self.bl_prop.default_value  ## TODO: Good idea?
+		return cached_value
+
+	def suppress_next_update(self, bl_instance) -> None:
+		self.suppress_update[bl_instance.instance_id] = True
+		## TODO: Make it a context manager to prevent the worst of surprises
+
+	def __set__(
+		self, bl_instance: bl_instance.BLInstance | None, value: typ.Any
+	) -> None:
+		"""Sets the value described by the BLField.
+
+		In general, any BLField modified in the UI will set `InvalidateCache` on this descriptor.
+		If `self.prop_info['use_prop_update']` is set, the method `bl_instance.on_prop_changed(self.bl_prop.name)` will then be called and start a `FlowKind.DataChanged` event chain.
+
+		Notes:
+			Run by Python when the attribute described by the descriptor is set.
+			For more, search for "Python descriptor protocol".
+
+		Parameters:
+			bl_instance: Instance that is accessing the attribute.
+			owner: The class that owns the instance.
+		"""
+		# Perform Update Chain
+		## -> We still respect 'use_prop_update', since it is user-sourced.
+		if value is Signal.DoUpdate:
+			if self.prop_info['use_prop_update']:
+				bl_instance.on_prop_changed(self.bl_prop.name)
+
+		# Invalidate Cache
+		## -> This empties the non-persistent cache.
+		## -> As a result, the value must be reloaded from the property.
+		## The 'on_prop_changed' method on the bl_instance might also be called.
+		elif value is Signal.InvalidateCache or value is Signal.InvalidateCacheNoUpdate:
+			self.bl_prop.invalidate_nonpersist(bl_instance)
+
+			# Update Suppression
+			if self.suppress_update.get(bl_instance.instance_id):
+				self.suppress_update[bl_instance.instance_id] = False
+
+			# ELSE: Trigger Update Chain
+			elif self.prop_info['use_prop_update'] and value is Signal.InvalidateCache:
+				bl_instance.on_prop_changed(self.bl_prop.name)
+
+		# Reset Enum Items
+		elif value is Signal.ResetEnumItems:
+			# Retrieve Old Items
+			## -> This is verbatim what is being persisted, currently.
+			## -> len(0): Manually replaced w/fallback to guarantee >=len(1)
+			## -> Fallback element is 'NONE'.
+			_old_items: list[ct.BLEnumElement] = self.bl_prop_enum_items.read(
+				bl_instance
+			)
+			old_items = (
+				_old_items
+				if _old_items
+				else default_enum_items(self.bl_prop.is_enum_many)
+			)
+
+			# Retrieve Current Items
+			## -> len(0): Manually replaced w/fallback to guarantee >=len(1)
+			## -> Manually replaced fallback element is 'NONE'.
+			_current_items: list[ct.BLEnumElement] = self.enum_cb(bl_instance, None)
+			current_items = (
+				_current_items
+				if _current_items
+				else default_enum_items(self.bl_prop.is_enum_many)
+			)
+
+			# Compare Old | Current
+			## -> We don't involve non-persistent caches (they lie!)
+			## -> Since we persist the user callback directly, we can compare.
+			if old_items != current_items:
+				# Retrieve Old Enum Item
+				## -> This is verbatim what is being used.
+				## -> De-Coerce None -> 'NONE' to avoid special-cased search.
+				_old_item = self.bl_prop.read(bl_instance)
+				old_item = 'NONE' if _old_item is None else _old_item
+
+				# Swap Enum Items
+				## -> This is the hot stuff - the enum elements are overwritten.
+				## -> The safe_enum_cb will pick up on this immediately.
+				self.suppress_next_update(bl_instance)
+				self.bl_prop_enum_items.write(bl_instance, current_items)
+
+				# Old Item in Current Items
+				## -> It's possible that the old enum key is in the new enum.
+				## -> If so, the user will expect it to "remain".
+				## -> Thus, we set it - Blender sees a change, user doesn't.
+				## -> DO NOT trigger on_prop_changed (since "nothing changed").
+				if any(old_item == item[0] for item in current_items):
+					self.suppress_next_update(bl_instance)
+					self.bl_prop.write(bl_instance, old_item)
+					## -> TODO: Don't write if not needed.
+
+				# Old Item Not in Current Items
+				## -> In this case, fallback to the first current item.
+				## -> DO trigger on_prop_changed (since it changed!)
+				else:
+					_first_current_item = current_items[0][0]
+					first_current_item = (
+						_first_current_item if _first_current_item != 'NONE' else None
+					)
+
+					self.suppress_next_update(bl_instance)
+					self.bl_prop.write(bl_instance, first_current_item)
+
+					if self.prop_info['use_prop_update']:
+						bl_instance.on_prop_changed(self.bl_prop.name)
+
+		# Reset Str Search
+		elif value is Signal.ResetStrSearch:
+			self.bl_prop_str_search.invalidate_nonpersist(bl_instance)
+
+		# General __set__
+		else:
+			self.bl_prop.write(bl_instance, value)
+
+			# Update Semantics
+			if self.suppress_update.get(bl_instance.instance_id):
+				self.suppress_update[bl_instance.instance_id] = False
+
+			elif self.prop_info['use_prop_update']:
+				bl_instance.on_prop_changed(self.bl_prop.name)
+
+	####################
+	# - Safe Callbacks
+	####################
+	def safe_str_cb(
+		self, _self: bl_instance.BLInstance, context: bpy.types.Context, edit_text: str
+	):
+		"""Wrapper around `StringProperty.search` which keeps a non-persistent cache around search results.
+
+		Reset by setting the descriptor to `Signal.ResetStrSearch`.
+		"""
+		cached_items = self.bl_prop_str_search.read_nonpersist(_self)
+		if cached_items is not Signal.CacheNotReady:
+			if cached_items is Signal.CacheEmpty:
+				computed_items = self.str_cb(_self, context, edit_text)
+				self.bl_prop_str_search.write_nonpersist(_self, computed_items)
+				return computed_items
+			return cached_items
+		return []
+
+	def safe_enum_cb(
+		self, _self: bl_instance.BLInstance, context: bpy.types.Context
+	) -> list[ct.BLEnumElement]:
+		"""Wrapper around `EnumProperty.items` callback, which **guarantees** that returned strings will not be GCed by keeping a persistent + non-persistent cache.
+
+		When a persistent cache exists, then the non-persistent cache will be filled at-will, since this is always guaranteed possible.
+		Otherwise, the persistent cache will only be regenerated when `Signal.ResetEnumItems` is run.
+		The original callback won't ever run other than then.
+
+		Until then, `DEFAULT_ENUM_ITEMS_MANY` or `DEFAULT_ENUM_ITEMS_SINGLE` will be used as defaults (guaranteed to not dereference so long as the module is loaded).
+		"""
+		# Compute Value (if available)
+		cached_items = self.bl_prop_enum_items.read_nonpersist(_self)
+		if cached_items is Signal.CacheNotReady or cached_items is Signal.CacheEmpty:
+			if _self is not None:
+				persisted_items = self.bl_prop_enum_items.read(_self)
+				if not persisted_items:
+					computed_items = self.enum_cb(_self, context)
+					_items = computed_items
+				else:
+					_items = persisted_items
+			else:
+				computed_items = self.enum_cb(_self, context)
+				_items = computed_items
+
+			# Fallback for Empty Persisted Items
+			## -> Use [('NONE', ...)]
+			## -> This guarantees that the enum items always has >=len(1)
+			items = _items if _items else default_enum_items(self.bl_prop.is_enum_many)
+
+			# Write Items -> Non-Persistent Cache
+			self.bl_prop_enum_items.write_nonpersist(_self, items)
+			return items
+		return cached_items

src/blender_maxwell/utils/bl_cache/bl_prop.py

@@ -0,0 +1,235 @@
+# blender_maxwell
+# Copyright (C) 2024 blender_maxwell Project Contributors
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Defines `BLProp`, a high-level wrapper for interacting with Blender properties."""
+
+import dataclasses
+import functools
+import typing as typ
+
+from blender_maxwell.utils import bl_instance, logger
+
+from . import managed_cache
+from .bl_prop_type import BLPropInfo, BLPropType
+from .signal import Signal
+
+log = logger.get(__name__)
+
+
+####################
+# - Blender Property (Abstraction)
+####################
+@dataclasses.dataclass(kw_only=True, frozen=True)
+class BLProp:
+	"""A high-level wrapper encapsulating access to a Blender property.
+
+	Attributes:
+		name: The name of the Blender property, as one uses it.
+		prop_info: Specifies the property's particular behavior, including subtype and UI.
+		prop_type: The type to associate with the property.
+			Especially relevant for structured deserialization.
+		bl_prop_type: Identifier encapsulating which Blender property used for data storage, and how.
+	"""
+
+	name: str
+	prop_info: BLPropInfo  ## TODO: Validate / Typing
+	prop_type: type
+	bl_prop_type: BLPropType
+
+	####################
+	# - Computed
+	####################
+	@functools.cached_property
+	def bl_name(self):
+		"""Deduces the actual attribute name at which the Blender property will be available."""
+		return f'blfield__{self.name}'
+
+	@functools.cached_property
+	def enum_cache_key(self):
+		"""Deduces an attribute name for use by the persistent cache component of `EnumProperty.items`.
+
+		For dynamic enums, a persistent cache is not enough - a non-persistent cache must also be used to guarantee that returned strings will not dereference.
+		**Letting dynamic enum strings dereference causes Blender to crash**.
+
+		Use of a non-persistent cache alone introduces a massive startup burden, as _all_ of the potentially expensive `EnumProperty.items` methods must re-run.
+		Should any depend on ex. internet connectivity, which is no longer available, elaborate failure modes may trigger.
+
+		By using this key, we can persist `items` for re-caching on startup, to reap the benefits of both schemes and make dynamic `EnumProperty` usable in practice.
+		"""
+		return self.name + '__enum_cache'
+
+	@functools.cached_property
+	def str_cache_key(self):
+		"""Deduce an internal name for string-search names distinct from the property name.
+
+		Compared to dynamic enums, string-search names are very gentle.
+		However, the mechanism is otherwise almost same, so similar logic makes a lot of sense.
+		"""
+		return self.name + '__str_cache'
+
+	@functools.cached_property
+	def display_name(self):
+		"""Deduce a display name for the Blender property, assigned to the `name=` attribute."""
+		return (
+			'[JSON] ' if self.bl_prop_type == BLPropType.Serialized else ''
+		) + f'BLField: {self.name}'
+
+	@functools.cached_property
+	def is_enum_many(self):
+		return self.bl_prop_type in [BLPropType.SetEnum, BLPropType.SetDynEnum]
+
+	####################
+	# - Low-Level Methods
+	####################
+	def encode(self, value: typ.Any):
+		"""Encode a value for compatibility with this Blender property, using the encapsulated types.
+
+		A convenience method for `BLPropType.encode()`.
+		"""
+		return self.bl_prop_type.encode(value)
+
+	@functools.cached_property
+	def default_value(self) -> typ.Any:
+		return self.prop_info.get('default')
+
+	def decode(self, value: typ.Any):
+		"""Encode a value for compatibility with this Blender property, using the encapsulated types.
+
+		A convenience method for `BLPropType.decode()`.
+		"""
+		return self.bl_prop_type.decode(value, self.prop_type)
+
+	####################
+	# - Initialization
+	####################
+	def init_bl_type(
+		self,
+		bl_type: type[bl_instance.BLInstance],
+		depends_on: frozenset[str] = frozenset(),
+		enum_depends_on: frozenset[str] | None = None,
+		strsearch_depends_on: frozenset[str] | None = None,
+	) -> None:
+		"""Declare the Blender property on a Blender class, ensuring that the property will be available to all `bl_instance.BLInstance` respecting instances of that class.
+
+		- **Declare BLField**: Runs `bl_type.declare_blfield()` to ensure that `on_prop_changed` will invalidate the cache for this property.
+		- **Set Property**: Runs `bl_type.set_prop()` to ensure that the Blender property will be available on instances of `bl_type`.
+
+		Parameters:
+			obj_type: The exact object type that will be stored in the Blender property.
+				**Must** be chosen such that `BLPropType.from_type(obj_type) == self`.
+		"""
+		# Parse KWArgs for Blender Property
+		kwargs_prop = self.bl_prop_type.parse_kwargs(
+			self.prop_type,
+			self.prop_info,
+		)
+
+		# Set Blender Property
+		bl_type.declare_blfield(
+			self.name,
+			self.bl_name,
+			use_dynamic_enum=self.prop_info.get('enum_dynamic', False),
+			use_str_search=self.prop_info.get('str_search', False),
+		)
+		bl_type.set_prop(
+			self.bl_name,
+			self.bl_prop_type.bl_prop,
+			# Property Options
+			name=self.display_name,
+			**kwargs_prop,
+		)  ## TODO: Parse __doc__ for property descs
+
+		for src_prop_name in depends_on:
+			bl_type.declare_blfield_dep(src_prop_name, self.name)
+
+		if self.prop_info.get('enum_dynamic', False) and enum_depends_on is not None:
+			for src_prop_name in enum_depends_on:
+				bl_type.declare_blfield_dep(
+					src_prop_name, self.name, method='reset_enum'
+				)
+
+		if self.prop_info.get('str_search', False) and strsearch_depends_on is not None:
+			for src_prop_name in strsearch_depends_on:
+				bl_type.declare_blfield_dep(
+					src_prop_name, self.name, method='reset_strsearch'
+				)
+
+	####################
+	# - Instance Methods
+	####################
+	def read_nonpersist(self, bl_instance: bl_instance.BLInstance | None) -> typ.Any:
+		"""Read the non-persistent cache value for this property.
+
+		Returns:
+			Generally, the cache value, with two exceptions.
+
+			- `Signal.CacheNotReady`: When either `bl_instance` is None, or it doesn't yet have a unique `bl_instance.instance_id`.
+				Indicates that the instance is not yet ready for use.
+				For nodes, `init()` has not yet run.
+				For sockets, `preinit()` has not yet run.
+
+			- `Signal.CacheEmpty`: When the cache has no entry.
+				A good idea might be to fill it immediately with `self.write_nonpersist(bl_instance)`.
+		"""
+		return managed_cache.read(
+			bl_instance,
+			self.bl_name,
+			use_nonpersist=True,
+			use_persist=False,
+		)
+
+	def read(self, bl_instance: bl_instance.BLInstance) -> typ.Any:
+		"""Read the Blender property's particular value on the given `bl_instance`."""
+		persisted_value = self.decode(
+			managed_cache.read(
+				bl_instance,
+				self.bl_name,
+				use_nonpersist=False,
+				use_persist=True,
+			)
+		)
+		if persisted_value is not Signal.CacheEmpty:
+			return persisted_value
+
+		msg = f"{self.name}: Can't read BLProp from instance {bl_instance}"
+		raise ValueError(msg)
+
+	def write(self, bl_instance: bl_instance.BLInstance, value: typ.Any) -> None:
+		managed_cache.write(
+			bl_instance,
+			self.bl_name,
+			self.encode(value),
+			use_nonpersist=False,
+			use_persist=True,
+		)
+		self.write_nonpersist(bl_instance, value)
+
+	def write_nonpersist(
+		self, bl_instance: bl_instance.BLInstance, value: typ.Any
+	) -> None:
+		managed_cache.write(
+			bl_instance,
+			self.bl_name,
+			value,
+			use_nonpersist=True,
+			use_persist=False,
+		)
+
+	def invalidate_nonpersist(self, bl_instance: bl_instance.BLInstance | None) -> None:
+		managed_cache.invalidate_nonpersist(
+			bl_instance,
+			self.bl_name,
+		)

src/blender_maxwell/utils/bl_cache/bl_prop_type.py

@@ -0,0 +1,755 @@
+# blender_maxwell
+# Copyright (C) 2024 blender_maxwell Project Contributors
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Defines `BLPropType`, which provides stronger lower-level interfaces for interacting with data that can be conformed to work with Blender properties."""
+
+import builtins
+import enum
+import functools
+import inspect
+import pathlib
+import typing as typ
+from pathlib import Path
+
+import bpy
+import numpy as np
+
+from blender_maxwell import contracts as ct
+from blender_maxwell.utils import logger, serialize
+from blender_maxwell.utils.staticproperty import staticproperty
+
+from .signal import Signal
+
+log = logger.get(__name__)
+
+####################
+# - Types
+####################
+BLIDStructs = typ.get_args(ct.BLIDStruct)
+Shape: typ.TypeAlias = None | tuple[int, ...]
+BLPropInfo: typ.TypeAlias = dict[str, typ.Any]
+
+
+@functools.cache
+def _parse_vector_size(obj_type: type[tuple[int, ...]]) -> int:
+	"""Parse the size of an arbitrarily sized generic tuple type, which is representing a vector.
+
+	Parameters:
+		obj_type: The type of a flat, generic tuple integer, representing a static vector shape.
+
+	Returns:
+		The length of any object that has the given type.
+	"""
+	return len(typ.get_args(obj_type))
+
+
+@functools.cache
+def _parse_matrix_size(obj_type: type[tuple[int, ...], ...]) -> tuple[int, int]:
+	"""Parse the rows and columns of an arbitrarily sized generic tuple-of-tuple type, which is representing a row-major matrix.
+
+	Parameters:
+		obj_type: The type of a singly-nested, generic tuple integer, representing a static matrix shape.
+
+	Returns:
+		The rows and columns of any object that has the given type.
+	"""
+	rows = len(typ.get_args(obj_type))
+	cols = len(typ.get_args(typ.get_args(obj_type)[0]))
+
+	for i, col_generic in enumerate(typ.get_args(obj_type)):
+		col_els = typ.get_args(col_generic)
+		if len(col_els) != cols:
+			msg = f'Value {obj_type} has mismatching column length {i} (to column 0)'
+			raise ValueError(msg)
+
+	return (rows, cols)
+
+
+def _is_strenum(T: type) -> bool:  # noqa: N803
+	return inspect.isclass(T) and issubclass(T, enum.StrEnum)
+
+
+####################
+# - Blender Property Type
+####################
+class BLPropType(enum.StrEnum):
+	"""A type identifier which can be directly associated with a Blender property.
+
+	For general use, the higher-level interface `BLProp` is more appropriate.
+
+	This is a low-level interface to Blender properties, allowing for directly identifying and utilizing a subset of types that are trivially representable using Blender's property system.
+	This hard-coded approach is especially required when managing the nuances of UI methods.
+
+	`BLPropType` should generally be treated as a "dumb" enum identifying the low-level representation of an object in a Blender property.
+	Use of `BLPropType.from_type` is encouraged; use of other methods is generally discouraged outside of higher-level encapsulating interfaces.
+
+
+	Attributes:
+		Bool: A boolean.
+		Int: An integer.
+		Float: A floating point number.
+		BoolVector: Between 2 and 32 booleans.
+		IntVector: Between 2 and 32 integers.
+		FloatVector: Between 2 and 32 floats.
+		BoolVector: 2D booleans of 2 - 32 elements per axis.
+		IntVector: 2D integers of 2 - 32 elements per axis.
+		FloatVector: 2D floats of 2 - 32 elements per axis.
+		Str: A simple string.
+		Path: A particular filesystem path.
+		SingleEnum: A single string value from a statically known `StrEnum`.
+		SetEnum: A set of string values, each from a statically known `StrEnum`.
+		SingleDynEnum: A single string value from a dynamically computed set of string values.
+		SetDynEnum: A set of string value, each from a dynamically computed set of string values.
+		BLPointer: A reference to a Blender object.
+			Blender manages correctly reconstructing this reference on startup, and the underlying pointer value is not stable.
+		Serialized: An arbitrary, serialized representation of an object.
+	"""
+
+	# Scalar
+	Bool = enum.auto()
+	Int = enum.auto()
+	Float = enum.auto()
+	## TODO: Support complex
+
+	# Vector
+	BoolVector = enum.auto()
+	IntVector = enum.auto()
+	FloatVector = enum.auto()
+
+	# Matrix
+	BoolMatrix = enum.auto()
+	IntMatrix = enum.auto()
+	FloatMatrix = enum.auto()
+
+	## TODO: Support jaxtyping JAX arrays (as serialized) directly?
+
+	# String
+	Str = enum.auto()
+	Path = enum.auto()
+	## TODO: OS checks for Path
+
+	# Enums
+	SingleEnum = enum.auto()
+	SetEnum = enum.auto()
+
+	SingleDynEnum = enum.auto()
+	SetDynEnum = enum.auto()
+
+	# Special
+	BLPointer = enum.auto()
+	Serialized = enum.auto()
+
+	####################
+	# - Static
+	####################
+	@staticproperty
+	def vector_types() -> frozenset[typ.Self]:
+		"""The set of `BLPropType`s that are considered "vectors"."""
+		BPT = BLPropType
+		return frozenset({BPT.BoolVector, BPT.IntVector, BPT.FloatVector})
+
+	@staticproperty
+	def matrix_types() -> frozenset[typ.Self]:
+		"""The set of `BLPropType`s that are considered "matrices"."""
+		BPT = BLPropType
+		return frozenset({BPT.BoolMatrix, BPT.IntMatrix, BPT.FloatMatrix})
+
+	####################
+	# - Computed
+	####################
+	@functools.cached_property
+	def is_vector(self) -> bool:
+		"""Checks whether this `BLPropType` is considered a vector.
+
+		Returns:
+			A boolean indicating "vectorness".
+		"""
+		return self in BLPropType.vector_types
+
+	@functools.cached_property
+	def is_matrix(self) -> bool:
+		"""Checks whether this `BLPropType` is considered a matrix.
+
+		Returns:
+			A boolean indicating "matrixness".
+		"""
+		return self in BLPropType.matrix_types
+
+	@functools.cached_property
+	def bl_prop(self) -> bpy.types.Property:
+		"""Deduce which `bpy.props.*` type should implement this `BLPropType` in practice.
+
+		In practice, `self.parse_kwargs()` collects arguments usable by the type returned by this property.
+		Thus, this property provides the key bridge between `BLPropType` and vanilla Blender properties.
+
+		Returns:
+			A Blender property type, for use as a constructor.
+		"""
+		BPT = BLPropType
+		return {
+			# Scalar
+			BPT.Bool: bpy.props.BoolProperty,
+			BPT.Int: bpy.props.IntProperty,
+			BPT.Float: bpy.props.FloatProperty,
+			# Vector
+			BPT.BoolVector: bpy.props.BoolVectorProperty,
+			BPT.IntVector: bpy.props.IntVectorProperty,
+			BPT.FloatVector: bpy.props.FloatVectorProperty,
+			# Matrix
+			BPT.BoolMatrix: bpy.props.BoolVectorProperty,
+			BPT.IntMatrix: bpy.props.IntVectorProperty,
+			BPT.FloatMatrix: bpy.props.FloatVectorProperty,
+			# String
+			BPT.Str: bpy.props.StringProperty,
+			BPT.Path: bpy.props.StringProperty,
+			# Enum
+			BPT.SingleEnum: bpy.props.EnumProperty,
+			BPT.SetEnum: bpy.props.EnumProperty,
+			BPT.SingleDynEnum: bpy.props.EnumProperty,
+			BPT.SetDynEnum: bpy.props.EnumProperty,
+			# Special
+			BPT.BLPointer: bpy.props.PointerProperty,
+			BPT.Serialized: bpy.props.StringProperty,
+		}[self]
+
+	@functools.cached_property
+	def primitive_type(self) -> type:
+		"""The "primitive" type representable using this property.
+
+		Generally, "primitive" types are Python standard library types.
+		However, exceptions may exist for a ubiquitously used type.
+
+		Returns:
+			A type guaranteed to be representable as a Blender property via. `self.encode()`.
+
+			Note that any relevant constraints on the type are not taken into account in this type.
+			For example, `SingleEnum` has `str`, even though all strings are not valid.
+			Similarly for ex. non-negative integers simply returning `int`.
+		"""
+		BPT = BLPropType
+		return {
+			# Scalar
+			BPT.Bool: bool,
+			BPT.Int: int,
+			BPT.Float: float,
+			# Vector
+			BPT.BoolVector: bool,
+			BPT.IntVector: int,
+			BPT.FloatVector: float,
+			# Matrix
+			BPT.BoolMatrix: bool,
+			BPT.IntMatrix: int,
+			BPT.FloatMatrix: float,
+			# String
+			BPT.Str: str,
+			BPT.Path: Path,
+			# Enum
+			BPT.SingleEnum: str,
+			BPT.SetEnum: set[str],
+			BPT.SingleDynEnum: str,
+			BPT.SetDynEnum: set[str],
+			# Special
+			BPT.BLPointer: None,
+			BPT.Serialized: str,
+		}[self]
+
+	####################
+	# - Parser Methods
+	####################
+	def parse_size(self, obj_type: type) -> Shape:
+		"""Retrieve the shape / shape of data associated with this `BLPropType`.
+
+		Returns:
+			Vectors have `(size,)`.
+			Matrices have `(rows, cols)`.
+
+			Otherwise, `None` indicates a single value/scalar.
+		"""
+		BPT = BLPropType
+
+		match self:
+			case BPT.BoolVector | BPT.IntVector | BPT.FloatVector:
+				return _parse_vector_size(obj_type)
+			case BPT.BoolMatrix | BPT.IntMatrix | BPT.FloatMatrix:
+				return _parse_matrix_size(obj_type)
+			case _:
+				return None
+
+	####################
+	# - KWArg Parsers
+	####################
+	@functools.cached_property
+	def required_info(self) -> list[str]:
+		"""Retrieve a list of required keyword arguments to the constructor returned by `self.bl_prop`.
+
+		Mainly useful via `self.check_info()`.
+
+		Returns:
+			A list of required keys for the Blender property constructor.
+		"""
+		BPT = BLPropType
+		return {
+			# Scalar
+			BPT.Bool: ['default'],
+			BPT.Int: ['default'],
+			BPT.Float: ['default'],
+			# Vector
+			BPT.BoolVector: ['default'],
+			BPT.IntVector: ['default'],
+			BPT.FloatVector: ['default'],
+			# Matrix
+			BPT.BoolMatrix: ['default'],
+			BPT.IntMatrix: ['default'],
+			BPT.FloatMatrix: ['default'],
+			# String
+			BPT.Str: ['default', 'str_search'],
+			BPT.Path: ['default', 'path_type'],
+			# Enum
+			BPT.SingleEnum: ['default'],
+			BPT.SetEnum: ['default'],
+			BPT.SingleDynEnum: ['enum_dynamic'],
+			BPT.SetDynEnum: ['enum_dynamic'],
+			# Special
+			BPT.BLPointer: ['blptr_type'],
+			BPT.Serialized: [],
+		}[self]
+
+	def check_info(self, prop_info: BLPropInfo) -> bool:
+		"""Validate that a dictionary contains all required entries needed when creating a Blender property.
+
+		Returns:
+			True if the provided dictionary is guaranteed to result in a valid Blender property when used as keyword arguments in the `self.bl_prop` constructor.
+		"""
+		return all(
+			required_info_key in prop_info for required_info_key in self.required_info
+		)
+
+	def parse_kwargs(  # noqa: PLR0915, PLR0912, C901
+		self,
+		obj_type: type,
+		prop_info: BLPropInfo,
+	) -> BLPropInfo:
+		"""Parse the kwargs dictionary used to construct the Blender property.
+
+		Parameters:
+			obj_type: The exact object type that will be stored in the Blender property.
+				**Generally** should be chosen such that `BLPropType.from_type(obj_type) == self`.
+			prop_info: The property info.
+				**Must** contain keys such that `required_info`
+
+		Returns:
+			Keyword arguments, which can be passed directly as to `self.bl_type` to construct a Blender property according to the `prop_info`.
+
+			In total, creating a Blender property can be done simply using `self.bl_type(**parse_kwargs(...))`.
+		"""
+		BPT = BLPropType
+
+		# Check Availability of Required Information
+		## -> All required fields must be defined.
+		if not self.check_info(prop_info):
+			msg = f'{self} ({obj_type}): Required property attribute is missing from prop_info="{prop_info}"'
+			raise ValueError(msg)
+
+		# Define Information -> KWArg Getter
+		def g_kwarg(name: str, force_key: str | None = None):
+			key = force_key if force_key is not None else name
+			return {key: prop_info[name]} if prop_info.get(name) is not None else {}
+
+		# Encode Default Value
+		if prop_info.get('default', Signal.CacheEmpty) is not Signal.CacheEmpty:
+			encoded_default = {'default': self.encode(prop_info.get('default'))}
+		else:
+			encoded_default = {}
+
+		# Assemble KWArgs
+		kwargs = {}
+		match self:
+			case BPT.Bool if obj_type is bool:
+				kwargs |= encoded_default
+
+			case BPT.Int | BPT.IntVector | BPT.IntMatrix:
+				kwargs |= encoded_default
+				kwargs |= g_kwarg('abs_min')
+				kwargs |= g_kwarg('abs_max')
+				kwargs |= g_kwarg('soft_min')
+				kwargs |= g_kwarg('soft_max')
+
+			case BPT.Float | BPT.FloatVector | BPT.FloatMatrix:
+				kwargs |= encoded_default
+				kwargs |= g_kwarg('abs_min')
+				kwargs |= g_kwarg('abs_max')
+				kwargs |= g_kwarg('soft_min')
+				kwargs |= g_kwarg('soft_max')
+				kwargs |= g_kwarg('step')
+				kwargs |= g_kwarg('precision')
+
+			case BPT.Str if obj_type is str:
+				kwargs |= encoded_default
+
+				# Str: Secret
+				if prop_info.get('str_secret'):
+					kwargs |= {'subtype': 'PASSWORD', 'options': {'SKIP_SAVE'}}
+
+				# Str: Search
+				if prop_info.get('str_search'):
+					kwargs |= g_kwarg('safe_str_cb', force_key='search')
+
+			case BPT.Path if obj_type is Path:
+				kwargs |= encoded_default
+
+				# Path: File/Dir
+				if prop_info.get('path_type'):
+					kwargs |= {
+						'subtype': (
+							'FILE_PATH'
+							if prop_info['path_type'] == 'file'
+							else 'DIR_PATH'
+						)
+					}
+
+			# Explicit Enums
+			case BPT.SingleEnum:
+				SubStrEnum = obj_type
+
+				# Static | Dynamic Enum
+				## -> Dynamic enums are responsible for respecting type.
+				if prop_info.get('enum_dynamic'):
+					kwargs |= g_kwarg('safe_enum_cb', force_key='items')
+				else:
+					kwargs |= encoded_default
+					kwargs |= {
+						'items': [
+							## TODO: Parse __doc__ for item descs
+							(
+								str(value),
+								SubStrEnum.to_name(value),
+								SubStrEnum.to_name(value),
+								SubStrEnum.to_icon(value),
+								i,
+							)
+							for i, value in enumerate(list(obj_type))
+						]
+					}
+
+			case BPT.SetEnum:
+				SubStrEnum = typ.get_args(obj_type)[0]
+
+				# Enum Set: Use ENUM_FLAG option.
+				kwargs |= {'options': {'ENUM_FLAG'}}
+
+				# Static | Dynamic Enum
+				## -> Dynamic enums are responsible for respecting type.
+				if prop_info.get('enum_dynamic'):
+					kwargs |= g_kwarg('safe_enum_cb', force_key='items')
+				else:
+					kwargs |= encoded_default
+					kwargs |= {
+						'items': [
+							## TODO: Parse __doc__ for item descs
+							(
+								str(value),
+								SubStrEnum.to_name(value),
+								SubStrEnum.to_name(value),
+								SubStrEnum.to_icon(value),
+								2**i,
+							)
+							for i, value in enumerate(list(SubStrEnum))
+						]
+					}
+
+			# Anonymous Enums
+			case BPT.SingleDynEnum:
+				kwargs |= g_kwarg('safe_enum_cb', force_key='items')
+
+			case BPT.SetDynEnum:
+				kwargs |= g_kwarg('safe_enum_cb', force_key='items')
+
+				# Enum Set: Use ENUM_FLAG option.
+				kwargs |= {'options': {'ENUM_FLAG'}}
+
+			# BLPointer
+			case BPT.BLPointer:
+				kwargs |= encoded_default
+
+				# BLPointer: ID Type
+				kwargs |= g_kwarg('blptr_type', force_key='type')
+
+			# BLPointer
+			case BPT.Serialized:
+				kwargs |= encoded_default
+
+		# Match Size
+		## -> Matrices have inverted order to mitigate the Matrix Display Bug.
+		size = self.parse_size(obj_type)
+		if size is not None:
+			if self in [BPT.BoolVector, BPT.IntVector, BPT.FloatVector]:
+				kwargs |= {'size': size}
+			if self in [BPT.BoolMatrix, BPT.IntMatrix, BPT.FloatMatrix]:
+				kwargs |= {'size': size[::-1]}
+
+		return kwargs
+
+	####################
+	# - Encode Value
+	####################
+	def encode(self, value: typ.Any) -> typ.Any:  # noqa: PLR0911
+		"""Transform a value to a form that can be directly written to a Blender property.
+
+		Parameters:
+			value: A value which should be transformed into a form that can be written to the Blender property returned by `self.bl_type`.
+
+		Returns:
+			A value that can be written directly to the Blender property returned by `self.bl_type`.
+		"""
+		BPT = BLPropType
+		match self:
+			# Scalars: Coerce Losslessly
+			## -> We choose to be very strict, except for float.is_integer() -> int
+			case BPT.Bool if isinstance(value, bool):
+				return value
+			case BPT.Int if isinstance(value, int):
+				return value
+			case BPT.Int if isinstance(value, float) and value.is_integer():
+				return int(value)
+			case BPT.Float if isinstance(value, int | float):
+				return float(value)
+
+			# Vectors | Matrices: list()
+			## -> We could use tuple(), but list() works just as fine when writing.
+			## -> Later, we read back as tuple() to respect the type annotation.
+			## -> Part of the workaround for the Matrix Display Bug happens here.
+			case BPT.BoolVector | BPT.IntVector | BPT.FloatVector:
+				return list(value)
+			case BPT.BoolMatrix | BPT.IntMatrix | BPT.FloatMatrix:
+				rows = len(value)
+				cols = len(value[0])
+				return (
+					np.array(value, dtype=self.primitive_type)
+					.flatten()
+					.reshape([cols, rows])
+				).tolist()
+
+			# String
+			## -> NOTE: This will happily encode StrEnums->str if an enum isn't requested.
+			case BPT.Str if isinstance(value, str):
+				return value
+
+			# Path: Use Absolute-Resolved Stringified Path
+			## -> TODO: Watch out for OS-dependence.
+			case BPT.Path if isinstance(value, Path):
+				return str(value.resolve())
+
+			# Empty Enums
+			## -> Coerce None to 'NONE', since 'NONE' is injected by convention.
+			case (
+				BPT.SingleEnum
+				| BPT.SetEnum
+				| BPT.SingleDynEnum
+				| BPT.SetDynEnum
+			) if value is None:
+				return 'NONE'
+
+			# Single Enum: Coerce to str
+			## -> isinstance(StrEnum.Entry, str) always returns True; thus, a good sanity check.
+			## -> Explicit/Dynamic both encode to str; only decode() coersion differentiates.
+			case BPT.SingleEnum | BPT.SingleDynEnum if isinstance(value, str):
+				return str(value)
+
+			# Single Enum: Coerce to set[str]
+			case BPT.SetEnum | BPT.SetDynEnum if isinstance(value, set):
+				return {str(v) for v in value}
+
+			# BLPointer: Don't Alter
+			case BPT.BLPointer if value in BLIDStructs or value is None:
+				return value
+
+			# Serialized: Serialize To UTF-8
+			## -> TODO: Check serializability
+			case BPT.Serialized:
+				return serialize.encode(value).decode('utf-8')
+
+		msg = f'{self}: No encoder defined for argument {value}'
+		raise NotImplementedError(msg)
+
+	####################
+	# - Decode Value
+	####################
+	def decode(self, raw_value: typ.Any, obj_type: type) -> typ.Any:  # noqa: PLR0911
+		"""Transform a raw value from a form read directly from the Blender property returned by `self.bl_type`, to its intended value of approximate type `obj_type`.
+
+		Notes:
+			`obj_type` is only a hint - for example, `obj_type = enum.StrEnum` is an indicator for a dynamic enum.
+			Its purpose is to guide ex. sizing and `StrEnum` coersion, not to guarantee a particular output type.
+
+		Parameters:
+			value: A value which should be transformed into a form that can be written to the Blender property returned by `self.bl_type`.
+
+		Returns:
+			A value that can be written directly to the Blender property returned by `self.bl_type`.
+		"""
+		BPT = BLPropType
+		match self:
+			# Scalars: Inverse Coerce (~Losslessly)
+			## -> We choose to be very strict, except for float.is_integer() -> int
+			case BPT.Bool if isinstance(raw_value, bool):
+				return raw_value
+			case BPT.Int if isinstance(raw_value, int):
+				return raw_value
+			case BPT.Int if isinstance(raw_value, float) and raw_value.is_integer():
+				return int(raw_value)
+			case BPT.Float if isinstance(raw_value, float):
+				return float(raw_value)
+
+			# Vectors | Matrices: tuple() to match declared type annotation.
+			## -> Part of the workaround for the Matrix Display Bug happens here.
+			case BPT.BoolVector | BPT.IntVector | BPT.FloatVector:
+				return tuple(raw_value)
+			case BPT.BoolMatrix | BPT.IntMatrix | BPT.FloatMatrix:
+				rows, cols = self.parse_size(obj_type)
+				return tuple(
+					map(tuple, np.array(raw_value).flatten().reshape([rows, cols]))
+				)
+
+			# String
+			## -> NOTE: This will happily decode StrEnums->str if an enum isn't requested.
+			case BPT.Str if isinstance(raw_value, str):
+				return raw_value
+
+			# Path: Use 'Path(abspath(*))'
+			## -> TODO: Watch out for OS-dependence.
+			case BPT.Path if isinstance(raw_value, str):
+				return Path(bpy.path.abspath(raw_value))
+
+			# Empty Enums
+			## -> Coerce 'NONE' to None, since 'NONE' is injected by convention.
+			## -> Using coerced 'NONE' as guaranteed len=0 element is extremely helpful.
+			case (
+				BPT.SingleEnum
+				| BPT.SetEnum
+				| BPT.SingleDynEnum
+				| BPT.SetDynEnum
+			) if raw_value in ['NONE']:
+				return None
+
+			# Explicit Enum: Coerce to predefined StrEnum
+			## -> This happens independent of whether there's a enum_cb.
+			case BPT.SingleEnum if isinstance(raw_value, str):
+				return obj_type(raw_value)
+			case BPT.SetEnum if isinstance(raw_value, set):
+				return {obj_type(v) for v in raw_value}
+
+			## Dynamic Enums: Nothing to coerce to.
+			## -> The critical distinction is that dynamic enums can't be coerced beyond str.
+			## -> All dynamic enums have an enum_cb, but this is merely a symptom of ^.
+			case BPT.SingleDynEnum if isinstance(raw_value, str):
+				return raw_value
+			case BPT.SetDynEnum if isinstance(raw_value, set):
+				return raw_value
+
+			# BLPointer
+			## -> None is always valid when it comes to BLPointers.
+			case BPT.BLPointer if raw_value in BLIDStructs or raw_value is None:
+				return raw_value
+
+			# Serialized: Deserialize the Argument
+			case BPT.Serialized:
+				return serialize.decode(obj_type, raw_value)
+
+		msg = f'{self}: No decoder defined for argument {raw_value}'
+		raise NotImplementedError(msg)
+
+	####################
+	# - Parse Type
+	####################
+	@staticmethod
+	def from_type(obj_type: type) -> typ.Self:  # noqa: PLR0911, PLR0912, C901
+		"""Select an appropriate `BLPropType` to store objects of the given type.
+
+		Use of this method is especially handy when attempting to represent arbitrary, type-annotated objects using Blender properties.
+		For example, the ability of the `BLPropType` to be displayed in a UI is prioritized as much as possible in making this decision.
+
+		Parameters:
+			obj_type: A type like `bool`, `str`, or custom classes.
+
+		Returns:
+			A `BLPropType` capable of storing any object of `obj_type`.
+		"""
+		BPT = BLPropType
+
+		# Match Simple
+		match obj_type:
+			case builtins.bool:
+				return BPT.Bool
+			case builtins.int:
+				return BPT.Int
+			case builtins.float:
+				return BPT.Float
+			case builtins.str:
+				return BPT.Str
+			case pathlib.Path:
+				return BPT.Path
+			case enum.StrEnum:
+				return BPT.SingleDynEnum
+			case _:
+				pass
+
+		# Match Arrays
+		## -> This deconstructs generic statements like ex. tuple[int, int]
+		typ_origin = typ.get_origin(obj_type)
+		typ_args = typ.get_args(obj_type)
+		if typ_origin is tuple and len(typ_args) > 0:
+			# Match Vectors
+			## -> ONLY respect homogeneous types
+			if all(T is bool for T in typ_args):
+				return BPT.BoolVector
+			if all(T is int for T in typ_args):
+				return BPT.IntVector
+			if all(T is float for T in typ_args):
+				return BPT.FloatVector
+
+			# Match Matrices
+			## -> ONLY respect twice-nested homogeneous types
+			## -> TODO: Explicitly require regularized shape, as in _parse_matrix_size
+			typ_args_args = [typ_arg for T0 in typ_args for typ_arg in typ.get_args(T0)]
+			if typ_args_args:
+				if all(T is bool for T in typ_args_args):
+					return BPT.BoolMatrix
+				if all(T is int for T in typ_args_args):
+					return BPT.IntMatrix
+				if all(T is float for T in typ_args_args):
+					return BPT.FloatMatrix
+
+		# Match SetDynEnum
+		## -> We can't do this in the match statement
+		if obj_type == set[enum.StrEnum]:
+			return BPT.SetDynEnum
+
+		# Match Static Enums
+		## -> Match Single w/Helper Function
+		if _is_strenum(obj_type):
+			return BPT.SingleEnum
+
+		## -> Match Set w/Helper Function
+		if typ_origin is set and len(typ_args) == 1 and _is_strenum(typ_args[0]):
+			return BPT.SetEnum
+
+		# Match BLPointers
+		if obj_type in BLIDStructs:
+			return BPT.BLPointer
+
+		# Fallback: Serializable Object
+		## -> TODO: Check serializability.
+		return BPT.Serialized

src/blender_maxwell/utils/bl_cache/cached_bl_property.py

@@ -0,0 +1,246 @@
+# blender_maxwell
+# Copyright (C) 2024 blender_maxwell Project Contributors
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Implements various key caches on instances of Blender objects, especially nodes and sockets."""
+
+import inspect
+import typing as typ
+
+from blender_maxwell.utils import bl_instance, logger, serialize
+
+from .bl_prop import BLProp
+from .bl_prop_type import BLPropType
+from .signal import Signal
+
+log = logger.get(__name__)
+
+####################
+# - Types
+####################
+PropGetMethod: typ.TypeAlias = typ.Callable[
+	[bl_instance.BLInstance], serialize.NaivelyEncodableType
+]
+PropSetMethod: typ.TypeAlias = typ.Callable[
+	[bl_instance.BLInstance, serialize.NaivelyEncodableType], None
+]
+
+
+####################
+# - CachedBLProperty
+####################
+class CachedBLProperty:
+	"""A descriptor that caches a computed attribute of a Blender node/socket/... instance (`bl_instance`).
+
+	Generally used via the associated decorator, `cached_bl_property`.
+
+	Notes:
+		It's like `@cached_property`, but on each Blender Instance ID.
+
+	Attributes:
+		getter_method: Method of `bl_instance` that computes the value.
+		setter_method: Method of `bl_instance` that sets the value.
+	"""
+
+	def __init__(
+		self,
+		getter_method: PropGetMethod,
+		persist: bool = False,
+		depends_on: frozenset[str] = frozenset(),
+	):
+		"""Initialize the getter of the cached property.
+
+		Parameters:
+			getter_method: Method of `bl_instance` that computes the value.
+		"""
+		self.getter_method: PropGetMethod = getter_method
+		self.setter_method: PropSetMethod | None = None
+
+		self.persist: bool = persist
+		self.depends_on: frozenset[str] = depends_on
+
+		self.bl_prop: BLProp | None = None
+
+		self.decode_type: type = inspect.signature(getter_method).return_annotation
+
+		# Check Non-Empty Type Annotation
+		## For now, just presume that all types can be encoded/decoded.
+		if self.decode_type is inspect.Signature.empty:
+			msg = f'A CachedBLProperty was instantiated, but its getter method "{self.getter_method}" has no return type annotation'
+			raise TypeError(msg)
+
+	def __set_name__(self, owner: type[bl_instance.BLInstance], name: str) -> None:
+		"""Generates the property name from the name of the attribute that this descriptor is assigned to.
+
+		Notes:
+			- Run by Python when setting an instance of this class to an attribute.
+
+		Parameters:
+			owner: The class that contains an attribute assigned to an instance of this descriptor.
+			name: The name of the attribute that an instance of descriptor was assigned to.
+		"""
+		self.bl_prop = BLProp(
+			name=name,
+			prop_info={'use_prop_update': True},
+			prop_type=self.decode_type,
+			bl_prop_type=BLPropType.Serialized,
+		)
+		self.bl_prop.init_bl_type(owner, depends_on=self.depends_on)
+
+	def __get__(
+		self,
+		bl_instance: bl_instance.BLInstance | None,
+		owner: type[bl_instance.BLInstance],
+	) -> typ.Any:
+		"""Retrieves the property from a cache, or computes it and fills the cache(s).
+
+		Parameters:
+			bl_instance: The Blender object this prop
+		"""
+		cached_value = self.bl_prop.read_nonpersist(bl_instance)
+		if cached_value is Signal.CacheNotReady or cached_value is Signal.CacheEmpty:
+			if bl_instance is not None:
+				if self.persist:
+					value = self.bl_prop.read(bl_instance)
+				else:
+					value = self.getter_method(bl_instance)
+
+				self.bl_prop.write_nonpersist(bl_instance, value)
+				return value
+			return Signal.CacheNotReady
+		return cached_value
+
+	def __set__(
+		self, bl_instance: bl_instance.BLInstance | None, value: typ.Any
+	) -> None:
+		"""Runs the user-provided setter, after invalidating the caches.
+
+		Notes:
+			- This invalidates all caches without re-filling them.
+			- The caches will be re-filled on the first `__get__` invocation, which may be slow due to having to run the getter method.
+
+		Parameters:
+			bl_instance: The Blender object this prop
+		"""
+		if value is Signal.DoUpdate:
+			bl_instance.on_prop_changed(self.bl_prop.name)
+
+		elif value is Signal.InvalidateCache or value is Signal.InvalidateCacheNoUpdate:
+			# Invalidate Partner Non-Persistent Caches
+			## -> Only for the invalidation case do we also invalidate partners.
+			if bl_instance is not None:
+				# Fill Caches
+				## -> persist: Fill Persist and Non-Persist Cache
+				## -> else: Fill Non-Persist Cache
+				if self.persist:
+					self.bl_prop.write(bl_instance, self.getter_method(bl_instance))
+
+				else:
+					self.bl_prop.write_nonpersist(
+						bl_instance, self.getter_method(bl_instance)
+					)
+
+				if value == Signal.InvalidateCache:
+					bl_instance.on_prop_changed(self.bl_prop.name)
+
+		elif self.setter_method is not None:
+			# Run Setter
+			## -> The user-provided setter should do any updating of partners.
+			if self.setter_method is not None:
+				self.setter_method(bl_instance, value)
+
+			# Fill Non-Persistant (and maybe Persistent) Cache
+			if self.persist:
+				self.bl_prop.write(bl_instance, self.getter_method(bl_instance))
+
+			else:
+				self.bl_prop.write_nonpersist(
+					bl_instance, self.getter_method(bl_instance)
+				)
+			bl_instance.on_prop_changed(self.bl_prop.name)
+
+		else:
+			msg = f'Tried to set "{value}" to "{self.prop_name}" on "{bl_instance.bl_label}", but a setter was not defined'
+			raise NotImplementedError(msg)
+
+	def setter(self, setter_method: PropSetMethod) -> typ.Self:
+		"""Decorator to add a setter to the cached property.
+
+		Returns:
+			The same descriptor, so that use of the same method name for defining a setter won't change the semantics of the attribute.
+
+		Examples:
+			Without the decorator, it looks like this:
+			```python
+			class Test(bpy.types.Node):
+				bl_label = 'Default'
+				...
+				def method(self) -> str: return self.bl_label
+				attr = CachedBLProperty(getter_method=method)
+
+				@attr.setter
+				def attr(self, value: str) -> None:
+					self.bl_label = 'Altered'
+			```
+		"""
+		# Validate Setter Signature
+		setter_sig = inspect.signature(setter_method)
+
+		## Parameter Length
+		if (sig_len := len(setter_sig.parameters)) != 2:  # noqa: PLR2004
+			msg = f'Setter method for "{self.prop_name}" should have 2 parameters, not "{sig_len}"'
+			raise TypeError(msg)
+
+		## Parameter Value Type
+		if (sig_ret_type := setter_sig.return_annotation) is not None:
+			msg = f'Setter method for "{self.prop_name}" return value type "{sig_ret_type}", but it should be "None" (omitting an annotation does not imply "None")'
+			raise TypeError(msg)
+
+		self.setter_method = setter_method
+		return self
+
+
+####################
+# - Decorator
+####################
+def cached_bl_property(
+	persist: bool = False,
+	depends_on: frozenset[str] = frozenset(),
+):
+	"""Decorator creating a descriptor that caches a computed attribute of a Blender node/socket.
+
+	Many such `bl_instance`s rely on fast access to computed, cached properties, for example to ensure that `draw()` remains effectively non-blocking.
+
+	Notes:
+		- Unfortunately, `functools.cached_property` doesn't work.
+		- Use `cached_attribute` if not using a node/socket.
+
+	Examples:
+	```python
+		class CustomNode(bpy.types.Node):
+			@bl_cache.cached()
+			def computed_prop(self) -> ...: return ...
+
+		print(bl_instance.prop)  ## Computes first time
+		print(bl_instance.prop)  ## Cached (after restart, will recompute)
+	```
+	"""
+
+	def decorator(getter_method: typ.Callable[[bl_instance.BLInstance], None]) -> type:
+		return CachedBLProperty(
+			getter_method=getter_method, persist=persist, depends_on=depends_on
+		)
+
+	return decorator

src/blender_maxwell/utils/bl_cache/keyed_cache.py

@@ -0,0 +1,146 @@
+# blender_maxwell
+# Copyright (C) 2024 blender_maxwell Project Contributors
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import functools
+import inspect
+import typing as typ
+
+from blender_maxwell.utils import bl_instance, logger, serialize
+
+log = logger.get(__name__)
+
+
+class KeyedCache:
+	def __init__(
+		self,
+		func: typ.Callable,
+		exclude: set[str],
+		encode: set[str],
+	):
+		# Function Information
+		self.func: typ.Callable = func
+		self.func_sig: inspect.Signature = inspect.signature(self.func)
+
+		# Arg -> Key Information
+		self.exclude: set[str] = exclude
+		self.include: set[str] = set(self.func_sig.parameters.keys()) - exclude
+		self.encode: set[str] = encode
+
+		# Cache Information
+		self.key_schema: tuple[str, ...] = tuple(
+			[
+				arg_name
+				for arg_name in self.func_sig.parameters
+				if arg_name not in exclude
+			]
+		)
+		self.caches: dict[str | None, dict[tuple[typ.Any, ...], typ.Any]] = {}
+
+	@property
+	def is_method(self):
+		return 'self' in self.exclude
+
+	def cache(self, instance_id: str | None) -> dict[tuple[typ.Any, ...], typ.Any]:
+		if self.caches.get(instance_id) is None:
+			self.caches[instance_id] = {}
+
+		return self.caches[instance_id]
+
+	def _encode_key(self, arguments: dict[str, typ.Any]):
+		## WARNING: Order of arguments matters. Arguments may contain 'exclude'd elements.
+		return tuple(
+			[
+				(
+					arg_value
+					if arg_name not in self.encode
+					else serialize.encode(arg_value)
+				)
+				for arg_name, arg_value in arguments.items()
+				if arg_name in self.include
+			]
+		)
+
+	def __get__(
+		self,
+		bl_instance: bl_instance.BLInstance | None,
+		owner: type[bl_instance.BLInstance],
+	) -> typ.Callable:
+		_func = functools.partial(self, bl_instance)
+		_func.invalidate = functools.partial(
+			self.__class__.invalidate, self, bl_instance
+		)
+		return _func
+
+	def __call__(self, *args, **kwargs):
+		# Test Argument Bindability to Decorated Function
+		try:
+			bound_args = self.func_sig.bind(*args, **kwargs)
+		except TypeError as ex:
+			msg = f'Can\'t bind arguments (args={args}, kwargs={kwargs}) to @keyed_cache-decorated function "{self.func.__name__}" (signature: {self.func_sig})"'
+			raise ValueError(msg) from ex
+
+		# Check that Parameters for Keying the Cache are Available
+		bound_args.apply_defaults()
+		all_arg_keys = set(bound_args.arguments.keys())
+		if not self.include <= (all_arg_keys - self.exclude):
+			msg = f'Arguments spanning the keyed cached ({self.include}) are not available in the non-excluded arguments passed to "{self.func.__name__}": {all_arg_keys - self.exclude}'
+			raise ValueError(msg)
+
+		# Create Keyed Cache Entry
+		key = self._encode_key(bound_args.arguments)
+		cache = self.cache(args[0].instance_id if self.is_method else None)
+		if (value := cache.get(key)) is None:
+			value = self.func(*args, **kwargs)
+			cache[key] = value
+
+		return value
+
+	def invalidate(
+		self,
+		bl_instance: bl_instance.BLInstance | None,
+		**arguments: dict[str, typ.Any],
+	) -> dict[str, typ.Any]:
+		# Determine Wildcard Arguments
+		wildcard_arguments = {
+			arg_name for arg_name, arg_value in arguments.items() if arg_value is ...
+		}
+
+		# Compute Keys to Invalidate
+		arguments_hashable = {
+			arg_name: serialize.encode(arg_value)
+			if arg_name in self.encode and arg_name not in wildcard_arguments
+			else arg_value
+			for arg_name, arg_value in arguments.items()
+		}
+		cache = self.cache(bl_instance.instance_id if self.is_method else None)
+		for key in list(cache.keys()):
+			if all(
+				arguments_hashable.get(arg_name) == arg_value
+				for arg_name, arg_value in zip(self.key_schema, key, strict=True)
+				if arg_name not in wildcard_arguments
+			):
+				cache.pop(key)
+
+
+def keyed_cache(exclude: set[str], encode: set[str] = frozenset()) -> typ.Callable:
+	def decorator(func: typ.Callable) -> typ.Callable:
+		return KeyedCache(
+			func,
+			exclude=exclude,
+			encode=encode,
+		)
+
+	return decorator

src/blender_maxwell/utils/bl_cache/managed_cache.py

@@ -0,0 +1,171 @@
+# blender_maxwell
+# Copyright (C) 2024 blender_maxwell Project Contributors
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Implements various key caches on instances of Blender objects, especially nodes and sockets."""
+
+## TODO: Note that persist=True on cached_bl_property may cause a draw method to try and write to a Blender property, which Blender disallows.
+
+import typing as typ
+
+from blender_maxwell import contracts as ct
+from blender_maxwell.utils import bl_instance, logger
+
+from .signal import Signal
+
+log = logger.get(__name__)
+
+
+####################
+# - Global Variables
+####################
+_CACHE_NONPERSIST: dict[bl_instance.InstanceID, dict[typ.Hashable, typ.Any]] = {}
+
+
+####################
+# - Create/Invalidate
+####################
+def bl_instance_nonpersist_cache(
+	bl_instance: bl_instance.BLInstance,
+) -> dict[typ.Hashable, typ.Any]:
+	"""Retrieve the non-persistent cache of a BLInstance."""
+	# Create Non-Persistent Cache Entry
+	## Prefer explicit cache management to 'defaultdict'
+	if _CACHE_NONPERSIST.get(bl_instance.instance_id) is None:
+		_CACHE_NONPERSIST[bl_instance.instance_id] = {}
+
+	return _CACHE_NONPERSIST[bl_instance.instance_id]
+
+
+def invalidate_nonpersist_instance_id(instance_id: bl_instance.InstanceID) -> None:
+	"""Invalidate any `instance_id` that might be utilizing cache space in `_CACHE_NONPERSIST`.
+
+	Notes:
+		This should be run by the `instance_id` owner in its `free()` method.
+
+	Parameters:
+		instance_id: The ID of the Blender object instance that's being freed.
+	"""
+	_CACHE_NONPERSIST.pop(instance_id, None)
+
+
+####################
+# - Access
+####################
+def read(
+	bl_instance: bl_instance.BLInstance | None,
+	key: typ.Hashable,
+	use_nonpersist: bool = True,
+	use_persist: bool = False,
+) -> typ.Any | typ.Literal[Signal.CacheNotReady, Signal.CacheEmpty]:
+	"""Read the cache associated with a Blender Instance, without writing to it.
+
+	Attributes:
+		key: The name to read from the instance-specific cache.
+		use_nonpersist: If true, will always try the non-persistent cache first.
+		use_persist: If true, will always try accessing the attribute `bl_instance,key`, where `key` is the value of the same-named parameter.
+			Generally, such an attribute should be a `bpy.types.Property`.
+
+	Return:
+		The cache hit, if any; else `Signal.CacheEmpty`.
+	"""
+	# Check BLInstance Readiness
+	if bl_instance is None:
+		return Signal.CacheNotReady
+
+	# Try Hit on Persistent Cache
+	if use_persist:
+		value = getattr(bl_instance, key, Signal.CacheEmpty)
+		if value is not Signal.CacheEmpty:
+			return value
+
+	# Check if Instance ID is Available
+	if not bl_instance.instance_id:
+		log.debug(
+			"Can't Get CachedBLProperty: Instance ID not (yet) defined on bl_instance.BLInstance %s",
+			str(bl_instance),
+		)
+		return Signal.CacheNotReady
+
+	# Try Hit on Non-Persistent Cache
+	if use_nonpersist:
+		cache_nonpersist = bl_instance_nonpersist_cache(bl_instance)
+		value = cache_nonpersist.get(key, Signal.CacheEmpty)
+		if value is not Signal.CacheEmpty:
+			return value
+
+	return Signal.CacheEmpty
+
+
+def write(
+	bl_instance: bl_instance.BLInstance,
+	key: typ.Hashable,
+	value: typ.Any,  ## TODO: "Serializable" type
+	use_nonpersist: bool = True,
+	use_persist: bool = False,
+) -> None:
+	"""Write to the cache associated with a Blender Instance.
+
+	Attributes:
+		key: The name to write to the instance-specific cache.
+		use_nonpersist: If true, will always write to the non-persistent cache first.
+		use_persist: If true, will always write to attribute `bl_instance.key`, where `key` is the value of the same-named parameter.
+			Generally, such an attribute should be a `bpy.types.Property`.
+		call_on_prop_changed: Whether to trigger `bl_instance.on_prop_changed()` with the
+	"""
+	# Check BLInstance Readiness
+	if bl_instance is None:
+		return
+
+	# Try Write on Persistent Cache
+	if use_persist:
+		# log.critical('%s: Writing %s to %s.', str(bl_instance), str(value), str(key))
+		setattr(bl_instance, key, value)
+
+	if not bl_instance.instance_id:
+		log.debug(
+			"Can't Get CachedBLProperty: Instance ID not (yet) defined on bl_instance.BLInstance %s",
+			str(bl_instance),
+		)
+		return
+
+	# Try Write on Non-Persistent Cache
+	if use_nonpersist:
+		cache_nonpersist = bl_instance_nonpersist_cache(bl_instance)
+		cache_nonpersist[key] = value
+
+
+def invalidate_nonpersist(
+	bl_instance: bl_instance.BLInstance,
+	key: typ.Hashable,
+) -> None:
+	"""Invalidate a particular key of the non-persistent cache.
+
+	**Persistent caches can't be invalidated without writing to them**.
+	To get the same effect, consider using `write()` to write its default value (which must be manually tracked).
+	"""
+	# Check BLInstance Readiness
+	if bl_instance is None:
+		return
+	if not bl_instance.instance_id:
+		log.debug(
+			"Can't Get CachedBLProperty: Instance ID not (yet) defined on bl_instance.BLInstance %s",
+			str(bl_instance),
+		)
+		return
+
+	# Retrieve Non-Persistent Cache
+	cache_nonpersist = bl_instance_nonpersist_cache(bl_instance)
+	cache_nonpersist.pop(key, None)

src/blender_maxwell/utils/bl_cache/signal.py

@@ -0,0 +1,61 @@
+# blender_maxwell
+# Copyright (C) 2024 blender_maxwell Project Contributors
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import enum
+import uuid
+
+
+class Signal(enum.StrEnum):
+	"""A value used to signal the descriptor via its `__set__`.
+
+	Such a signal **must** be entirely unique: Even a well-thought-out string could conceivably produce a very nasty bug, where instead of setting a descriptor-managed attribute, the user would inadvertently signal the descriptor.
+
+	To make it effectively impossible to confuse any other object whatsoever with a signal, the enum values are set to per-session `uuid.uuid4()`.
+
+	Notes:
+		**Do not** use this enum for anything other than directly signalling a `bl_cache` descriptor via its setter.
+
+		**Do not** store this enum `Signal` in a variable or method binding that survives longer than the session.
+
+		**Do not** persist this enum; the values will change whenever `bl_cache` is (re)loaded.
+
+	Attributes:
+		CacheNotReady: The cache isn't yet ready to be used.
+			Generally, this is because the `BLInstance` isn't made yet.
+		CacheEmpty: The cache has no information to offer.
+
+		InvalidateCache: The cache should be invalidated.
+		InvalidateCacheNoUpdate: The cache should be invalidated, but no update method should be run.
+		DoUpdate: Any update method that the cache triggers on change should be run.
+			An update is **not guaranteeed** to be run, merely requested.
+
+		ResetEnumItems: Cached dynamic enum items should be recomputed on next use.
+		ResetStrSearch: Cached string-search items should be recomputed on next use.
+	"""
+
+	# Cache Management
+	CacheNotReady: str = str(uuid.uuid4())
+	CacheEmpty: str = str(uuid.uuid4())
+
+	# Invalidation
+	InvalidateCache: str = str(uuid.uuid4())
+	InvalidateCacheNoUpdate: str = str(uuid.uuid4())
+	DoUpdate: str = str(uuid.uuid4())
+
+	# Reset Signals
+	## -> Invalidates data adjascent to fields.
+	ResetEnumItems: str = str(uuid.uuid4())
+	ResetStrSearch: str = str(uuid.uuid4())

src/blender_maxwell/utils/bl_instance.py

@@ -0,0 +1,299 @@
+# blender_maxwell
+# Copyright (C) 2024 blender_maxwell Project Contributors
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import typing as typ
+import uuid
+from types import MappingProxyType
+
+import bpy
+
+from blender_maxwell.utils import bl_cache, logger
+
+InstanceID: typ.TypeAlias = str  ## Stringified UUID4
+
+log = logger.get(__name__)
+
+
+class BLInstance:
+	"""An instance of a blender object, ex. nodes/sockets.
+
+	Used as a common base of functionality for nodes/sockets, especially when it comes to the magic introduced by `bl_cache`.
+
+	Notes:
+		All the `@classmethod`s are designed to be invoked with `cls` as the subclass of `BLInstance`, not `BLInstance` itself.
+
+		For practical reasons, introducing a metaclass here is not a good idea, and thus `abc.ABC` can't be used.
+		To this end, only `self.on_prop_changed` needs a subclass implementation.
+		It's a little sharp, but managable.
+
+		Inheritance schemes like this are generally not enjoyable.
+		However, the way Blender's node/socket classes are structured makes it the most practical way design for the functionality encapsulated here.
+
+	Attributes:
+		instance_id: Stringified UUID4 that uniquely identifies an instance, among all active instances on all active classes.
+	"""
+
+	####################
+	# - Attributes
+	####################
+	instance_id: bpy.props.StringProperty(default='')
+
+	blfields: typ.ClassVar[dict[str, str]] = MappingProxyType({})
+	blfield_deps: typ.ClassVar[dict[str, list[str]]] = MappingProxyType({})
+
+	blfields_dynamic_enum: typ.ClassVar[set[str]] = frozenset()
+	blfield_dynamic_enum_deps: typ.ClassVar[dict[str, list[str]]] = MappingProxyType({})
+
+	blfields_str_search: typ.ClassVar[set[str]] = frozenset()
+	blfield_str_search_deps: typ.ClassVar[dict[str, list[str]]] = MappingProxyType({})
+
+	####################
+	# - Runtime Instance Management
+	####################
+	def reset_instance_id(self) -> None:
+		"""Reset the Instance ID of a BLInstance.
+
+		The Instance ID is used to index the instance-specific cache, since Blender doesn't always directly support keeping changing data on node/socket instances.
+
+		Notes:
+			Should be run whenever the instance is copied, so that the copy will index its own cache.
+
+			The Instance ID is a `UUID4`, which is globally unique, negating the need for extraneous overlap-checks.
+		"""
+		self.instance_id = str(uuid.uuid4())
+		self.regenerate_dynamic_field_persistance()
+
+	@classmethod
+	def assert_attrs_valid(cls, mandatory_props: set[str]) -> None:
+		"""Asserts that all mandatory attributes are defined on the class.
+
+		The list of mandatory objects is generally sourced from a global variable, `MANDATORY_PROPS`, which should be passed to this function while running `__init_subclass__`.
+
+		Raises:
+			ValueError: If a mandatory attribute defined in `base.MANDATORY_PROPS` is not defined on the class.
+		"""
+		for cls_attr in mandatory_props:
+			if not hasattr(cls, cls_attr):
+				msg = f'Node class {cls} does not define mandatory attribute "{cls_attr}".'
+				raise ValueError(msg)
+
+	####################
+	# - Field Registration
+	####################
+	@classmethod
+	def declare_blfield(
+		cls,
+		attr_name: str,
+		bl_attr_name: str,
+		use_dynamic_enum: bool = False,
+		use_str_search: bool = False,
+	) -> None:
+		"""Declare the existance of a (cached) field and any properties affecting its invalidation.
+
+		Primarily, the `attr_name -> bl_attr_name` map will be available via the `cls.blfields` dictionary.
+		Thus, for use in UIs (where `bl_attr_name` must be used), one can use `cls.blfields[attr_name]`.
+
+		Parameters:
+			attr_name: The name of the attribute accessible via the instance.
+			bl_attr_name: The name of the attribute containing the Blender property.
+				This is used both as a persistant cache for `attr_name`, as well as (possibly) the data altered by the user from the UI.
+			use_dynamic_enum: Will mark `attr_name` as a dynamic enum.
+				Allows `self.regenerate_dynamic_field_persistance` to reset this property, whenever all dynamic `EnumProperty`s are reset at once.
+			use_str_searc: The name of the attribute containing the Blender property.
+				Allows `self.regenerate_dynamic_field_persistance` to reset this property, whenever all searched `StringProperty`s are reset at once.
+		"""
+		cls.blfields = cls.blfields | {attr_name: bl_attr_name}
+
+		if use_dynamic_enum:
+			cls.blfields_dynamic_enum = cls.blfields_dynamic_enum | {attr_name}
+
+		if use_str_search:
+			cls.blfields_str_search = cls.blfields_str_search | {attr_name}
+
+	@classmethod
+	def declare_blfield_dep(
+		cls,
+		src_prop_name: str,
+		dst_prop_name: str,
+		method: typ.Literal[
+			'invalidate', 'reset_enum', 'reset_strsearch'
+		] = 'invalidate',
+	) -> None:
+		"""Declare that `prop_name` relies on another property.
+
+		This is critical for cached, computed properties that must invalidate their cache whenever any of the data they rely on changes.
+		In practice, a chain of invalidation emerges naturally when this is put together, managed internally for performance.
+
+		Notes:
+			If the relevant `*_deps` dictionary is not defined on `cls`, we manually create it.
+			This shadows the relevant `BLInstance` attribute, which is an immutable `MappingProxyType` on purpose, precisely to prevent the situation of altering data that shouldn't be common to all classes inheriting from `BLInstance`.
+
+			Not clean, but it works.
+
+		Parameters:
+			dep_prop_name: The property that should, whenever changed, also invalidate the cache of `prop_name`.
+			prop_name: The property that relies on another property.
+		"""
+		match method:
+			case 'invalidate':
+				if not cls.blfield_deps:
+					cls.blfield_deps = {}
+				deps = cls.blfield_deps
+			case 'reset_enum':
+				if not cls.blfield_dynamic_enum_deps:
+					cls.blfield_dynamic_enum_deps = {}
+				deps = cls.blfield_dynamic_enum_deps
+			case 'reset_strsearch':
+				if not cls.blfield_str_search_deps:
+					cls.blfield_str_search_deps = {}
+				deps = cls.blfield_str_search_deps
+
+		if deps.get(src_prop_name) is None:
+			deps[src_prop_name] = []
+
+		deps[src_prop_name].append(dst_prop_name)
+
+	@classmethod
+	def set_prop(
+		cls,
+		bl_prop_name: str,
+		prop: bpy.types.Property,
+		**kwargs,
+	) -> None:
+		"""Adds a Blender property via `__annotations__`, so that it will be initialized on all subclasses.
+
+		**All Blender properties trigger an update method** when updated from the UI, in order to invalidate the non-persistent cache of the associated `BLField`.
+		Specifically, this behavior happens in `on_bl_prop_changed()`.
+
+		However, whether anything else happens after that invalidation is entirely up to the particular `BLField`.
+		Thus, `BLField` is put in charge of how/when updates occur.
+
+		Notes:
+			In general, Blender properties can't be set on classes directly.
+			They must be added as type annotations, which Blender will read and understand.
+
+			This is essentially a convenience method to encapsulate this unexpected behavior, as well as constrain the behavior of the `update` method somewhat.
+
+		Parameters:
+			bl_prop_name: The name of the property to set, as accessible from Blender.
+				Generally, from code, the user would access the wrapping `BLField` instead of directly accessing the `bl_prop_name` attribute.
+			prop: The `bpy.types.Property` to instantiate and attach..
+			kwargs: Constructor arguments to pass to the Blender property.
+				There are many mostly-documented nuances with these.
+				The methods of `bl_cache.BLPropType` are designed to provide more strict, helpful abstractions for practical use.
+		"""
+		cls.__annotations__[bl_prop_name] = prop(
+			update=lambda self, context: self.on_bl_prop_changed(bl_prop_name, context),
+			**kwargs,
+		)
+
+	####################
+	# - Runtime Field Management
+	####################
+	def regenerate_dynamic_field_persistance(self):
+		"""Regenerate the persisted data of all dynamic enums and str search BLFields.
+
+		In practice, this sets special "signal" values:
+		- **Dynamic Enums**: The signal value `bl_cache.Signal.ResetEnumItems` will be set, causing `BLField.__set__` to regenerate the enum items using the user-provided callback.
+		- **Searched Strings**: The signal value `bl_cache.Signal.ResetStrSearch` will be set, causing `BLField.__set__` to regenerate the available search strings using the user-provided callback.
+		"""
+		# Generate Enum Items
+		## -> This guarantees that the items are persisted from the start.
+		for dyn_enum_prop_name in self.blfields_dynamic_enum:
+			setattr(self, dyn_enum_prop_name, bl_cache.Signal.ResetEnumItems)
+
+		# Generate Str Search Items
+		## -> Match dynamic enum semantics
+		for str_search_prop_name in self.blfields_str_search:
+			setattr(self, str_search_prop_name, bl_cache.Signal.ResetStrSearch)
+
+	def on_bl_prop_changed(self, bl_prop_name: str, _: bpy.types.Context) -> None:
+		"""Called when a property has been updated via the Blender UI.
+
+		The only effect is to invalidate the non-persistent cache of the associated BLField.
+		The BLField then decides whether to take any other action, ex. calling `self.on_prop_changed()`.
+		"""
+		## TODO: What about non-Blender set properties?
+
+		# Strip the Internal Prefix
+		## -> TODO: This is a bit of a hack. Use a contracts constant.
+		prop_name = bl_prop_name.removeprefix('blfield__')
+		# log.debug(
+		# 'Callback on Property %s (stripped: %s)',
+		# bl_prop_name,
+		# prop_name,
+		# )
+		# log.debug(
+		# 'Dependencies (PROP: %s) (ENUM: %s) (SEAR: %s)',
+		# self.blfield_deps,
+		# self.blfield_dynamic_enum_deps,
+		# self.blfield_str_search_deps,
+		# )
+
+		# Invalidate Property Cache
+		## -> Only the non-persistent cache is regenerated.
+		## -> The BLField decides whether to trigger `on_prop_changed`.
+		if prop_name in self.blfields:
+			# RULE: =1 DataChanged per Dependency Chain
+			## -> We MUST invalidate the cache, but might not want to update.
+			## -> Update should only be triggered when ==0 dependents.
+			setattr(self, prop_name, bl_cache.Signal.InvalidateCacheNoUpdate)
+
+			# Invalidate Dependent Properties (incl. DynEnums and StrSearch)
+			## -> NOTE: Dependent props may also trigger `on_prop_changed`.
+			## -> Meaning, don't use extraneous dependencies (as usual).
+			for deps, invalidate_signal in zip(
+				[
+					self.blfield_deps,
+					self.blfield_dynamic_enum_deps,
+					self.blfield_str_search_deps,
+				],
+				[
+					bl_cache.Signal.InvalidateCache,
+					bl_cache.Signal.ResetEnumItems,
+					bl_cache.Signal.ResetStrSearch,
+				],
+				strict=True,
+			):
+				if prop_name in deps:
+					for dst_prop_name in deps[prop_name]:
+						# log.debug(
+						# 'Property %s is invalidating %s',
+						# prop_name,
+						# dst_prop_name,
+						# )
+						setattr(
+							self,
+							dst_prop_name,
+							invalidate_signal,
+						)
+
+			# Do Update AFTER Dependencies
+			## -> Yes, update will run once per dependency.
+			## -> Don't abuse dependencies :)
+			## -> If no-update is important, use_prop_update is still respected.
+			setattr(self, prop_name, bl_cache.Signal.DoUpdate)
+
+	def on_prop_changed(self, prop_name: str) -> None:
+		"""Triggers changes/an event chain based on a changed property.
+
+		In general, the `BLField` descriptor associated with `prop_name` decides whether this method should be called whenever `__set__` is used.
+		An indirect consequence of this is that `self.on_bl_prop_changed`, which is _always_ triggered, may only _sometimes_ result in `on_prop_changed` being called, at the discretion of the relevant `BLField`.
+
+		Notes:
+			**Must** be overridden on all `BLInstance` subclasses.
+		"""
+		raise NotImplementedError

src/blender_maxwell/utils/extra_sympy_units.py

@@ -96,6 +96,26 @@ class MathType(enum.StrEnum):
 			}[self]
 		)
 
+	def coerce_compatible_pyobj(
+		self, pyobj: bool | int | Fraction | float | complex
+	) -> bool | int | Fraction | float | complex:
+		MT = MathType
+		match self:
+			case MT.Bool:
+				return pyobj
+			case MT.Integer:
+				return int(pyobj)
+			case MT.Rational if isinstance(pyobj, int):
+				return Fraction(pyobj, 1)
+			case MT.Rational if isinstance(pyobj, Fraction):
+				return pyobj
+			case MT.Real:
+				return float(pyobj)
+			case MT.Complex if isinstance(pyobj, int | Fraction):
+				return complex(float(pyobj), 0)
+			case MT.Complex if isinstance(pyobj, float):
+				return complex(pyobj, 0)
+
 	@staticmethod
 	def from_expr(sp_obj: SympyType) -> type:
 		if isinstance(sp_obj, sp.MatrixBase):
@@ -124,21 +144,31 @@ class MathType(enum.StrEnum):
 		raise ValueError(msg)
 
 	@staticmethod
-	def from_pytype(dtype) -> type:
+	def from_pytype(dtype: type) -> type:
 		return {
 			bool: MathType.Bool,
 			int: MathType.Integer,
+			Fraction: MathType.Rational,
 			float: MathType.Real,
 			complex: MathType.Complex,
 		}[dtype]
 
+	@staticmethod
+	def has_mathtype(obj: typ.Any) -> typ.Literal['pytype', 'expr'] | None:
+		if isinstance(obj, bool | int | Fraction | float | complex):
+			return 'pytype'
+		if isinstance(obj, sp.Basic | sp.MatrixBase | sp.MutableDenseMatrix):
+			return 'expr'
+
+		return None
+
 	@property
 	def pytype(self) -> type:
 		MT = MathType
 		return {
 			MT.Bool: bool,
 			MT.Integer: int,
-			MT.Rational: float,
+			MT.Rational: Fraction,
 			MT.Real: float,
 			MT.Complex: complex,
 		}[self]
@@ -209,8 +239,20 @@ class NumberSize1D(enum.StrEnum):
 		)
 
 	@staticmethod
-	def supports_shape(shape: tuple[int, ...] | None):
-		return shape is None or (len(shape) == 1 and shape[0] in [2, 3])
+	def has_shape(shape: tuple[int, ...] | None):
+		return shape in [None, (2,), (3,), (4,), (2, 1), (3, 1), (4, 1)]
+
+	def supports_shape(self, shape: tuple[int, ...] | None):
+		NS = NumberSize1D
+		match self:
+			case NS.Scalar:
+				return shape is None
+			case NS.Vec2:
+				return shape in ((2,), (2, 1))
+			case NS.Vec3:
+				return shape in ((3,), (3, 1))
+			case NS.Vec4:
+				return shape in ((4,), (4, 1))
 
 	@staticmethod
 	def from_shape(shape: tuple[typ.Literal[2, 3]] | None) -> typ.Self:
@@ -220,6 +262,9 @@ class NumberSize1D(enum.StrEnum):
 			(2,): NS.Vec2,
 			(3,): NS.Vec3,
 			(4,): NS.Vec4,
+			(2, 1): NS.Vec2,
+			(3, 1): NS.Vec3,
+			(4, 1): NS.Vec4,
 		}[shape]
 
 	@property
@@ -233,6 +278,14 @@ class NumberSize1D(enum.StrEnum):
 		}[self]
 
 
+def symbol_range(sym: sp.Symbol) -> str:
+	return f'{sym.name} ∈ ' + (
+		'ℂ'
+		if sym.is_complex
+		else ('ℝ' if sym.is_real else ('ℤ' if sym.is_integer else '?'))
+	)
+
+
 ####################
 # - Unit Dimensions
 ####################
@@ -749,7 +802,7 @@ def scale_to_unit(sp_obj: SympyType, unit: spu.Quantity) -> Number:
 	Raises:
 		ValueError: If the result of unit-conversion and -stripping still has units, as determined by `uses_units()`.
 	"""
-	unitless_expr = spu.convert_to(sp_obj, unit) / unit
+	unitless_expr = spu.convert_to(sp_obj, unit) / unit if unit is not None else sp_obj
 	if not uses_units(unitless_expr):
 		return unitless_expr
 
@@ -800,6 +853,9 @@ def unit_str_to_unit(unit_str: str) -> Unit | None:
 class PhysicalType(enum.StrEnum):
 	"""Type identifiers for expressions with both `MathType` and a unit, aka a "physical" type."""
 
+	# Unitless
+	NonPhysical = enum.auto()
+
 	# Global
 	Time = enum.auto()
 	Angle = enum.auto()
@@ -845,10 +901,11 @@ class PhysicalType(enum.StrEnum):
 	AngularWaveVector = enum.auto()
 	PoyntingVector = enum.auto()
 
-	@property
+	@functools.cached_property
 	def unit_dim(self):
 		PT = PhysicalType
 		return {
+			PT.NonPhysical: None,
 			# Global
 			PT.Time: Dims.time,
 			PT.Angle: Dims.angle,
@@ -894,10 +951,11 @@ class PhysicalType(enum.StrEnum):
 			PT.PoyntingVector: Dims.power / Dims.length**2,
 		}[self]
 
-	@property
+	@functools.cached_property
 	def default_unit(self) -> list[Unit]:
 		PT = PhysicalType
 		return {
+			PT.NonPhysical: None,
 			# Global
 			PT.Time: spu.picosecond,
 			PT.Angle: spu.radian,
@@ -942,10 +1000,11 @@ class PhysicalType(enum.StrEnum):
 			PT.AngularWaveVector: spu.radian * terahertz,
 		}[self]
 
-	@property
+	@functools.cached_property
 	def valid_units(self) -> list[Unit]:
 		PT = PhysicalType
 		return {
+			PT.NonPhysical: [None],
 			# Global
 			PT.Time: [
 				femtosecond,
@@ -1101,12 +1160,13 @@ class PhysicalType(enum.StrEnum):
 		for physical_type in list(PhysicalType):
 			if unit in physical_type.valid_units:
 				return physical_type
+		## TODO: Optimize
 
-		msg = f'No PhysicalType found for unit {unit}'
+		msg = f'Could not determine PhysicalType for {unit}'
 		raise ValueError(msg)
 
-	@property
-	def valid_shapes(self):
+	@functools.cached_property
+	def valid_shapes(self) -> list[typ.Literal[(3,), (2,)] | None]:
 		PT = PhysicalType
 		overrides = {
 			# Cartesian
@@ -1133,7 +1193,7 @@ class PhysicalType(enum.StrEnum):
 
 		return overrides.get(self, [None])
 
-	@property
+	@functools.cached_property
 	def valid_mathtypes(self) -> list[MathType]:
 		"""Returns a list of valid mathematical types, especially whether it can be real- or complex-valued.
 
@@ -1157,6 +1217,7 @@ class PhysicalType(enum.StrEnum):
 		MT = MathType
 		PT = PhysicalType
 		overrides = {
+			PT.NonPhysical: list(MT),  ## Support All
 			# Cartesian
 			PT.Freq: [MT.Real, MT.Complex],  ## Im -> Growth/Damping
 			PT.AngFreq: [MT.Real, MT.Complex],  ## Im -> Growth/Damping
@@ -1187,6 +1248,8 @@ class PhysicalType(enum.StrEnum):
 
 	@staticmethod
 	def to_name(value: typ.Self) -> str:
+		if value is PhysicalType.NonPhysical:
+			return 'Unitless'
 		return PhysicalType(value).name
 
 	@staticmethod

src/blender_maxwell/utils/staticproperty.py

@@ -21,7 +21,7 @@ class staticproperty(property):  # noqa: N801
 	The decorated method must take no arguments whatsoever, including `self`/`cls`.
 
 	Examples:
-		Use as usual:
+		Exactly as you'd expect.
 		```python
 		class Spam:
 			@staticproperty