Blender Git Loki

Animation: add function to blend Action into pose

Add function `BKE_pose_apply_action_blend()`, which blends a given
Action into current pose. The Action is evaluated at a specified frame,
and the result is applied to the armature's pose.

A blend factor can be given to blend between the current pose and the
one in the Action. Quaternions are interpolated with SLERP; it is
assumed that their FCurves are consecutively stored in the Action.

This function will be used in the upcoming new Pose Library.

UI: New UI list layout type for big preview tiles

This new layout type is meant for the upcoming asset view UI template.
With it it is possible to show big asset previews with their names in a
responsive grid layout.

Notes:
* The layout is only available for C defined UI lists. We could expose
it to Python, but I think there are still some scrolling issues to be
fixed first. (The asset view template doesn't use scrolling for the UI
list.)
* I'd consider this a more usable version of the existing `GRID` layout
type. We may remove that in favor of the new one in future.

UI: Support defining UI lists in C

So far all UI lists had to be defined in Python, this makes it possible
to define them in C as well. Note that there is a whole bunch of special
handling for the Python API that isn't there for C. I think most
importantly custom properties support, which currently can't be added
for C defined UI lists.

The upcoming asset view UI template will use this, which needs to be
defined in C.

Adds a new file `interface_template_list.cc`, which at this point is
mostly a dummy to have a place for the `ED_uilisttypes_ui()` definition.
I plan a separate cleanup to move the UI-list template to that file.

UI: Support UI list tooltips, defined via Python scripts

Makes it possible to create tooltips for UI list rows, which can be
filled in .py scripts, similar to how they can extend other menus. This
is used by the (to be committed) Pose Library add-on to display pose
operations (selecting bones of a pose, blending a pose, etc).

It's important that the Python scripts check if the UI list is the
correct one by checking the list ID.
For this to work, a new `bpy.context.ui_list` can be checked. For
example, the Pose Library add-on does the following check:
```
def is_pose_asset_view() -> bool:
# Important: Must check context first, or the menu is added for every kind of list.
list = getattr(context, "ui_list", None)
if not list or list.bl_idname != "UI_UL_asset_view" or list.list_id != "pose_assets":
return False
if not context.asset_handle:
return False
return True
```

Assets: Abstraction for temporary loading of asset data-blocks

This is an editor-level abstraction for the `BLO_library_temp_xxx()`
API for temporary loading of data-blocks from another Blend file. It
abstracts away the asset specific code, like asset file-path handling
and local asset data-block handling.

Main use-case for this is applying assets as presets that are based on
data-blocks, like poses. Such preset assets are an important part of the
asset system design, so such an abstraction will likely find more usage
in the future.

UI/Assets: Initial Asset View UI template

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
```

Assets: AssetHandle type as temporary design to reference assets

With temporary I mean that this is not intended to be part of the
eventual asset system design. For that we are planning to have an
`AssetRepresentation` instead, see T87235. Once the `AssetList` is
implemented (see T88184), that would be the owner of the asset
representations.

However for the upcoming asset system, asset browser, asset view and
pose library commits we need some kind of asset handle to pass around.
That is what this commit introduces.
Idea is a handle to wrap the `FileDirEntry` representing the asset, and
an API to access its data (currently very small, will be extended in
further commits). So the fact that an asset is currently a file
internally is abstracted away. However: We have to expose it as file in
the Python API, because we can't return the asset-handle directly there,
for reasons explained in the code. So the active asset file is exposed
as `bpy.context.asset_file_handle`.

Animation: new pose library based on Asset Browser

Introduce new pose library, based on the Asset Browser. Contrary to the
old pose library (in `editors/armature/pose_lib.c`), which stored an
entire library of poses in an `Action`, in the new library each pose is
its own `Action` datablock. This is done for compatibility with the
asset browser, and also to make it easier to attach preview images,
share datablocks, etc. Furthermore, it opens the door to having
animation snippets in the pose library as well.

This commit contains the C code for the pose library; in order to fully
use it, an addon is required as well (which will be committed shortly).

Assets: Initial Asset List as part of the Asset System design

Implements a basic, WIP version of the asset list. This is needed to
give the asset view UI template asset reading and displaying
functionality.

See:
* Asset System: Data Storage, Reading & UI Access - https://developer.blender.org/T88184

Especially the asset list internals should change. It uses the
File/Asset Browser's `FileList` API, which isn't really meant for access
from outside the File Browser. But as explained in T88184, it does a lot
of the stuff we currently need, so we (Sybren St�vel and I) decided to
go this route for now. Work on a file-list rewrite which integrates well
with the asset system started in the `asset-system-filelist` branch.

Further includes:
* Operator to reload the asset list.
* New `bpy.types.AssetHandle.get_full_library_path()` function, which
gets the full path of the asset via the asset-list.
* Changes to preview loading to prevent the preview loading job to run
eternally for asset views. File Browsers have this issue too, but
should be fixed separately.

UI: UI list refactor & preparations for asset view template

This is more of a first-pass refactor for the UI list template. More
improvements could be done, but that's better done separately. Main
purpose of this is to make the UI list code more manageable and ready
for the asset view template.

No functional changes for users.

* Split the huge template function into more manageable functions, with
clear names and a few structs with high coherency.
* Move runtime data management to the template code, with a free
callback called from BKE. This is UI data and should be managed at
that level.
* Replace boolean arguments with bit-flags (easily extendable and more
readable from the caller).
* Allow passing custom-data to the UI list for callbacks to access.
* Make list grip button for resizing optional.
* Put logic for generating the internal UI list identifier (stored in
.blends) into function. This is a quite important bit and a later
commit adds a related function. Good to have a clear API for this.
* Improve naming, comments, etc.

As part of further cleanups I'd like to move this to an own file.

File/Asset Browser: Extend file-entry and asset handle Python API

Adds the following to `bpy.types.FileSelectEntry`:
* `id_type`: The data-block type the file represenets, if any.
* `local_id`: The local data-block it represents, if any (assets only).

And the following to `bpy.types.AssetHandle`:
* `local_id`: The local data-block the asset represents, if any.

This kind of information and the references are important for asset related
operators and UIs. They will be used by upcoming Pose Library features.

UI: Internal support for custom UI list item drag & activate operators

For pose libraries, we need to be able to apply a pose whenever
activating (clicking) an item in the Pose Library asset view and blend
it by dragging (press & move). And since we want to allow Python scripts
to define what happens at least when activating an asset (so they can
define for example a custom "Apply" operator for preset assets), it
makes sense to just let them pass an operator name to the asset view
template. The template will be introduced in a following commit.

Cleanup: Use const for UI icon getter function

Animation: apply pose to all or selected bones of armature

New function `BKE_pose_apply_action_all_bones()`, which will be
necessary for the upcoming pose library v2.0.

This renames the function `BKE_pose_apply_action` to
`BKE_pose_apply_action_selected_bones`, to reflect that it only works on
selected bones, to contrast it to the new function.

UI: Support left-right arrow key walk navigation in UI lists

Add improved arrow key walk navigation in grid layout UI List templates.
Pressing up or down walks the active item to the adjacent row in that
direction, while left and right walk through the items along the columns
wrapping at the rows.

Note from Julian:
In combination with the following commit, this has the important
limitation that the list's custom activate operator won't be called when
"walking over" an item that is scrolled out of the list. That is because
we don't actually create any buttons for those that could be used for
the handling logic. For our purposes of the pose libraries that should
be fine since the asset view list is always made big enough to display
all items. Solving this might be difficult, we don't properly support
nesting boxes with proper scrolling in regular layouts. It's all just
hacked a bit for UI-lists to work. Overlaps quite a bit with T86149.

Differential Revision: https://developer.blender.org/D11063

Fix T89870: Vertex groups lost when opening 3.0 files in 2.93

The original refactor for vertex groups (3b6ee8cee708)
forgot to bump the minimum file requirement.

I'm also bumping the subversion to 12 so everyone can switch to a
working subversion number.

Differential Revision: https://developer.blender.org/D11931

Cleanup: use raw strings, quiet clang-tidy warnings

Cleanup: improve comments, remove debug printf

Fix: missing null check

This was a regression in rB3b6ee8cee7080af200e25e944fe30d310240e138.

Cleanup: clang-format