In the `FileList` struct, rename the `AssetLibraryReference
*asset_library` field to `asset_library_ref` -- it's a description of
which asset library is used, and not the asset library itself.
This is to make space for a future `AssetLibrary *asset_library` field,
which will point to an actual asset library struct/class.
No functional changes.
Reviewed by: Severin
Differential Revision: https://developer.blender.org/D12151
Before this, all asset view templates showing the same asset library
would show the same assets, even if they should show different ID types.
That was a major limitation since the design did forsee that this
template can be put anywhere in the UI to display various sub-sets of
assets.
Initially I did the ID type filtering close to the asset-list reading,
because I wanted to optimize reading so that we would only actually read
asset information from disk of the ID type to be shown. But this will be
quite complex and I'm not sure if I'll get to work on this anytime soon.
So this commit moves the filtering to the template display level solving
this limitation.
Note: This also adds the code to filter by tags, together with the ID
type. But it's not actually used anywhere yet.
This iterator was introduced before `AssetHandle` existed, so it was
dealing with the file data directly. Now we want as little code as
possible to deal with the file data, all access should happen via the
`AssetHandle`.
Would previously pass a few properties that are available via the
asset-handle now. This asset-handle is also required for some of the
asset API, e.g. the temporary ID loading. This will probably be needed
before too long.
For this to work, the utility function needs to be callable without
context, which is only needed for a File Browser specific hack anyway
(doesn't apply to this usage of it).
While the asset-handle design is supposed to be temporary (see
35affaa971), I prefer keeping the fact that it's nothing but a file
entry pointer an implementation detail that is abstracted away. So this
introduces getters for the file data we typically access for
asset-handles.
The asset view UI template is a mini-version of the Asset Browser that
can be placed in regular layouts, regions or popups. At this point it's
made specifically for placement in vertical layouts, it can be made more
flexible in the future.
Generally the way this is implemented will likely change a lot still as
the asset system evolves.
The Pose Library add-on will use the asset view to display pose
libraries in the 3D View sidebar.
References:
* https://developer.blender.org/T86139
* https://code.blender.org/2021/06/asset-browser-project-update/#what-are-we-building
* https://code.blender.org/2021/05/pose-library-v2-0/#use-from-3d-viewport
Notes:
* Important limitation: Due to the early & WIP implementation of the
asset list, all asset views showing the same library will show the
same assets. That is despite the ID type filter option the template
provides. The first asset view created will determine what's visible.
Of course this should be made to work eventually.
* The template supports passing an activate and a drag operator name.
The former is called when an asset is clicked on (e.g. to apply the
asset) the latter when dragging (e.g. to .blend a pose asset). If no
drag operator is set, regular asset drag & drop will be executed.
* The template returns the properties for both operators (see example
below).
* The argument list for using the template is quite long, but we can't
avoid that currently. The UI list design requires that we pass a
number of RNA or custom properties to work with, that for the Pose
Libraries should be registered at the Pose Library add-on level, not
in core Blender.
* Idea is that Python scripts or add-ons that want to use the asset view
can register custom properties, to hold data like the list of assets,
and the active asset index. Maybe that will change in future and we
can manage these internally.
As an example, the pose library add-on uses it like this:
```
activate_op_props, drag_op_props = layout.template_asset_view(
"pose_assets",
workspace,
"active_asset_library",
wm,
"pose_assets",
workspace,
"active_pose_asset_index",
filter_id_types={"filter_action"},
activate_operator="poselib.apply_pose_asset",
drag_operator="poselib.blend_pose_asset",
)
drag_op_props.release_confirm = True
drag_op_props.flipped = wm.poselib_flipped
activate_op_props.flipped = wm.poselib_flipped
```
