This moves `PointCloud` to use the recently added `AttributeStorage`
at runtime. Mainly this involves implementing the higher level attribute
API on top, and implementing the RNA API as well. The attribute RNA type
is now backed by either CustomDataLayer or bke::Attribute. For now the
new code is specific to point clouds but next steps can reuse it for
Grease Pencil layer attributes, curves, and eventually meshes.
Point cloud attributes no longer have a name length limit.
Internally, the `AttributeStorage` API is extended with a few additions:
- The data structs have static constructors for convenience.
- A few functions give index-based access to attributes
- A "rename" function is added.
The `Attribute` RNA type now exposes a `storage_type` property.
For now the "single value" option is still unused at runtime, and
accessing the single value data isn't implemented yet.
Pull Request: https://projects.blender.org/blender/blender/pulls/139165
As described in #122398, implement read and write support for a new
attribute storage system. Currently this is only implemented to support
forward compatibility; the format used at runtime isn't changed at all.
That can be done one step at a time during the 4.5 and 5.0 development
cycles. A new experimental option for testing tells Blender to always
save with the new format.
The main benefit of the new structure is that it matches the attribute
system design, it allows for future attribute storage optimization, and
each attribute is an allocated struct, which will give pointer stability
for the Python API.
The next step is to connect the attribute API and the RNA API to
AttributeStorage for the simplest geometry type, point clouds.
Pull Request: https://projects.blender.org/blender/blender/pulls/133874
