Expose the convenience function `blender::animrig::action_fcurve_ensure()`
to RNA as `Action.fcurve_ensure_for_datablock(...)`.
The function requires that the Action is already assigned to the
data-block. It then takes care of slot assignment / creation, as well as
the creation of a layer and a keyframe strip.
This function call:
```python
fcurve = action.fcurve_ensure_for_datablock(ob_cube, "location", index=2)
```
effectively performs this logic:
```python
# Ensure the slot exists and is assigned:
slot = ob_cube.animation_data.slot
if not slot:
slot = find_slot_for_keying(action)
if not slot:
slot = action.slots.new(ob_cube.name)
ob_cube.animation_data.slot = slot
# Ensure a layer exists:
if action.layers:
layer = action.layers[0]
else:
layer = action.layers.new("Layer")
# Ensure a keyframe strip exists:
if layer.strips:
strip = layer.strips[0]
else:
strip = layer.strips.new('KEYFRAME')
# Ensure the channelbag exists:
channelbag = strip.channelbag(slot, ensure=True)
# Ensure the F-Curve exists:
fcurve = channelbag.fcurves.find("location", index=1)
if not fcurve:
fcurve = channelbag.fcurves.new("location", index=1)
```
Here `find_slot_for_keying()` represents the logic that's also used when
creating keys via the user interface or the `bpy_struct.keyframe_insert()`
function.
Pull Request: https://projects.blender.org/blender/blender/pulls/134686
2393d498cb