BLField has gotten a huge facelift, to make it practical to wrangle
properties without the sharp edges.
- All the "special" UI-exposed property types can now be directly
constructed in a BLField marked with 'prop_ui'.
- The most appropriate internal representation will be chosen to
represent the attribute based on its type annotation, including sized
vector-like `bool`, `int`, `float` for `tuple[...]`.
- Static EnumProperties can now be derived from a special `StrEnum`, to
which a `to_name` and `to_icon` method is attached.
- Dynamic `EnumProperty` can now be used safely, with builtin
workarounds to the real-world reference-loss-crash (realized
in the Tidy3D Cloud Task node) and jankiness like empty enum.
- The update method is now fully managed, negating all bugs related to
improper update callback naming.
- Python-side getter caching is preserved for ui-exposed
properties, with the help of node/socket base class support for
passing a `Signal.InvalidateCache` to BLFields that are altered in the
UI.
The cost to all this niceness is rather low, and arguably, positive:
- Dynamic Enum/String searchers no longer "magically" invoke all the
time, since the values seen by Blender are cached by the BLField.
- To regenerate the searcher output, an `@on_value_changed` should be
made by the user to pass `Signal.ResetEnumItems` or
`Signal.ResetStrSearch` to the `BLField`.
- Since searching is no longer eager, there is no danger of
out-of-reference strings (which crash Blender from EnumProperty), but
also a greatly reduced performance problems associated with
the hot-loop regeneration of EnumProperty strings.
- The base classes are now involved with BLField invalidation, to ensure
that the getter caches are cleared up when the UI changes. For the
price of that small indirection (done cheaply with set lookup),
all attribute lookups are generally done in a single lookup, completely
avoiding Blender until needed.
- This does represent another increase in confidence wrt. the event
system's integrity, but so far, that has been a very productive
direction.
**NOTE**: The entire feature set of BLField is not well tested, and will
likely need adjustments as the codebase is converted to use them.