Fix T61234 Mirroring Grease Pencil keyframes in the Dopesheet fails

`ANIM_animdata_update()` did not sort grease pencil frames. A
pre-existing comment stated this wouldn't be necessary as
`posttrans_gpd_clean()` already does this. However, this is only
applicable when the change is performed via the transform system. The
mirror operator doesn't call `posttrans_gpd_clean()`, invalidating the
assumption in the comment.

I moved the sorting code into `BKE_gpencil_layer_frames_sort()`, which
is now called from both `ANIM_animdata_update()` and
`posttrans_gpd_clean()`.

4 files changed, 29 insertions, 23 deletions

diff --git a/source/blender/blenkernel/BKE_gpencil.h b/source/blender/blenkernel/BKE_gpencil.h
index 128d5807ca3..5d23029df9e 100644
--- a/source/blender/blenkernel/BKE_gpencil.h
+++ b/source/blender/blenkernel/BKE_gpencil.h
@@ -193,6 +193,7 @@ void BKE_gpencil_layer_mask_remove_ref(struct bGPdata *gpd, const char *name);
 struct bGPDlayer_Mask *BKE_gpencil_layer_mask_named_get(struct bGPDlayer *gpl, const char *name);
 void BKE_gpencil_layer_mask_sort(struct bGPdata *gpd, struct bGPDlayer *gpl);
 void BKE_gpencil_layer_mask_sort_all(struct bGPdata *gpd);
+void BKE_gpencil_layer_frames_sort(struct bGPDlayer *gpl, bool *r_has_duplicate_frames);
 
 /* Brush */
 struct Material *BKE_gpencil_brush_material_get(struct Brush *brush);
diff --git a/source/blender/blenkernel/intern/gpencil.c b/source/blender/blenkernel/intern/gpencil.c
index c587e433e7f..c0b40721ccc 100644
--- a/source/blender/blenkernel/intern/gpencil.c
+++ b/source/blender/blenkernel/intern/gpencil.c
@@ -1120,6 +1120,32 @@ void BKE_gpencil_layer_mask_sort_all(bGPdata *gpd)
   }
 }
 
+static int gpencil_cb_cmp_frame(void *thunk, const void *a, const void *b)
+{
+  const bGPDframe *frame_a = a;
+  const bGPDframe *frame_b = b;
+
+  if (frame_a->framenum < frame_b->framenum) {
+    return -1;
+  }
+  if (frame_a->framenum > frame_b->framenum) {
+    return 1;
+  }
+  if (thunk != NULL) {
+    *((bool *)thunk) = true;
+  }
+  /* Sort selected last. */
+  if ((frame_a->flag & GP_FRAME_SELECT) && ((frame_b->flag & GP_FRAME_SELECT) == 0)) {
+    return 1;
+  }
+  return 0;
+}
+
+void BKE_gpencil_layer_frames_sort(struct bGPDlayer *gpl, bool *r_has_duplicate_frames)
+{
+  BLI_listbase_sort_r(&gpl->frames, gpencil_cb_cmp_frame, r_has_duplicate_frames);
+}
+
 /* get the active gp-layer for editing */
 bGPDlayer *BKE_gpencil_layer_active_get(bGPdata *gpd)
 {
diff --git a/source/blender/editors/animation/anim_deps.c b/source/blender/editors/animation/anim_deps.c
index 98fcb9c5ce5..439b8071deb 100644
--- a/source/blender/editors/animation/anim_deps.c
+++ b/source/blender/editors/animation/anim_deps.c
@@ -368,9 +368,7 @@ void ANIM_animdata_update(bAnimContext *ac, ListBase *anim_data)
       if (ale->update & ANIM_UPDATE_ORDER) {
         ale->update &= ~ANIM_UPDATE_ORDER;
         if (gpl) {
-          /* While correct & we could enable it: 'posttrans_gpd_clean' currently
-           * both sorts and removes doubles, so this is not necessary here. */
-          // gpencil_sort_frames(gpl);
+          BKE_gpencil_layer_frames_sort(gpl, NULL);
         }
       }
 
diff --git a/source/blender/editors/transform/transform_convert.c b/source/blender/editors/transform/transform_convert.c
index f93a3ec260b..4ccb97b7a00 100644
--- a/source/blender/editors/transform/transform_convert.c
+++ b/source/blender/editors/transform/transform_convert.c
@@ -830,25 +830,6 @@ bool FrameOnMouseSide(char side, float frame, float cframe)
 
 /* ********************* ACTION EDITOR ****************** */
 
-static int gpf_cmp_frame(void *thunk, const void *a, const void *b)
-{
-  const bGPDframe *frame_a = a;
-  const bGPDframe *frame_b = b;
-
-  if (frame_a->framenum < frame_b->framenum) {
-    return -1;
-  }
-  if (frame_a->framenum > frame_b->framenum) {
-    return 1;
-  }
-  *((bool *)thunk) = true;
-  /* selected last */
-  if ((frame_a->flag & GP_FRAME_SELECT) && ((frame_b->flag & GP_FRAME_SELECT) == 0)) {
-    return 1;
-  }
-  return 0;
-}
-
 static int masklay_shape_cmp_frame(void *thunk, const void *a, const void *b)
 {
   const MaskLayerShape *frame_a = a;
@@ -881,7 +862,7 @@ static void posttrans_gpd_clean(bGPdata *gpd)
     bGPDframe *gpf, *gpfn;
     bool is_double = false;
 
-    BLI_listbase_sort_r(&gpl->frames, gpf_cmp_frame, &is_double);
+    BKE_gpencil_layer_frames_sort(gpl, &is_double);
 
     if (is_double) {
       for (gpf = gpl->frames.first; gpf; gpf = gpfn) {