Grease Pencil animation channels are now also shown in the Dopesheet
mode of the Dopesheet editor and in the Timeline.
Grease pencil related events are now listened not only by container
`SACTCONT_GPENCIL` (Grease Pencil Dopesheet), but also
`SACTCONT_DOPESHEET` (main Dopesheet), and `SACTCONT_TIMELINE`
(timeline).
A new Animation Filter flag was added: `ANIMFILTER_FCURVESONLY`. For now
this only filters out Grease Pencil Layer channels.
**Implemented:**
- Preview range set: now only considers selected Grease Pencil keyframes
when `onlySel` parameter is true. Not only this allows the operator to
work with grease pencil keyframes in main dopesheet, but it also fixes
the operator in the Grease Pencil dopesheet.
- Translation: allocation (and freeing) of specific memory for
translation of Grease Pencil keyframes.
- Copy/Paste: call to both Fcurve and GPencil operators, to allow for
mixed selection. Errors are only reported when both the FCurve and
GPencil functions fail to paste anything.
- Keyframe Type change and Insert Keyframe: removed some code here to
unify Grease Pencil dopesheet and main dopesheet code.
- Jump, Snap, Mirror, Select all/box/lasso/circle, Select left/right,
Clickselect: account for Grease Pencil channels within the channels
loop, no need for `ANIMFILTER_FCURVESONLY` there.
**Not Implemented:**
- Graph-related operators. The filter `ANIMFILTER_FCURVESONLY` is
naively added to all graph-related operators, meaning more-or-less all
operators that used `ANIMFILTER_CURVE_VISIBLE`.
- Select linked: is for F-curves channel only
- Select more/less: not yet implemented for grease pencil layers.
- Clean Keys, Sample, Extrapolation, Interpolation, Easing, and Handle
type change: work on Fcurve-channels only, so the
`ANIMFILTER_FCURVESONLY` filter is activated
Graying out these operators (when no fcurve keyframe is selected) can be
done with custom poll functions BUT may affect performance. This is NOT
done in this patch.
**Dopesheet Summary Selection:**
The main summary of the dopesheet now also takes into account Grease
Pencil keyframes, using some nasty copy/pasting of code, as explained
[on devtalk](https://devtalk.blender.org/t/gpencil-layers-integration-in-main-dopesheet-selection-issue/24527).
It works, but may be improved, providing some deeper changes.
Reviewed By: mendio, pepeland, sybren
Maniphest Tasks: T97477
Differential Revision: https://developer.blender.org/D15003
92d7f9ac56