View2D: Inform region type on current view changes

Allows to hook per-space code which is to be run on view navigation.
This is required to have zoom-to-fit implemented in the sequencer.

There might be more cases where the clalback is to be called from,
but it could be easier to address those on the case-by-case basis
when its needed.

1 files changed, 10 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_screen.h b/source/blender/blenkernel/BKE_screen.h
index edab543fc37..1090deae93f 100644
--- a/source/blender/blenkernel/BKE_screen.h
+++ b/source/blender/blenkernel/BKE_screen.h
@@ -183,6 +183,16 @@ typedef struct ARegionType {
   /* return context data */
   int (*context)(const struct bContext *C, const char *member, struct bContextDataResult *result);
 
+  /* Is called whenever the current visible View2D's region changes.
+   *
+   * Used from user code such as view navigation/zoom operators to inform region about changes.
+   * The goal is to support zoom-to-fit features which gets disabled when manual navigation is
+   * performed.
+   *
+   * This callback is not called on indirect changes of the current viewport (which could happen
+   * when the `v2d->tot is changed and `cur` is adopted accordingly).  */
+  void (*on_view2d_changed)(const struct bContext *C, struct ARegion *region);
+
   /* custom drawing callbacks */
   ListBase drawcalls;