UI: Animation editor scrubbing area

The main reason for this change is to allow setting the
active frame with the left mouse button, while still being
able to select e.g. keyframes with the same mouse button.

The solution is to introduce a new scrubbing region with
a specialized keymap. There are a couple of related todos,
that will be handled in separate commits.
Those are listed in D4654.

This solves T63193.

Differential Revision: https://developer.blender.org/D4654

Reviewers: brecht, billreynish

1 files changed, 17 insertions, 5 deletions

diff --git a/source/blender/editors/screen/area.c b/source/blender/editors/screen/area.c
index 8c73f4cd649..6fe2b5eb37d 100644
--- a/source/blender/editors/screen/area.c
+++ b/source/blender/editors/screen/area.c
@@ -1566,6 +1566,13 @@ static bool event_in_markers_region(const ARegion *ar, const wmEvent *event)
   return BLI_rcti_isect_pt(&rect, event->x, event->y);
 }
 
+static bool event_in_scrubbing_region(const ARegion *ar, const wmEvent *event)
+{
+  rcti rect = ar->winrct;
+  rect.ymin = rect.ymax - UI_SCRUBBING_MARGIN_Y;
+  return BLI_rcti_isect_pt(&rect, event->x, event->y);
+}
+
 /**
  * \param ar: Region, may be NULL when adding handlers for \a sa.
  */
@@ -1604,14 +1611,19 @@ static void ed_default_handlers(
     wmKeyMap *keymap = WM_keymap_ensure(wm->defaultconf, "View2D", 0, 0);
     WM_event_add_keymap_handler(handlers, keymap);
   }
-  if (flag & ED_KEYMAP_MARKERS) {
+  if (flag & ED_KEYMAP_ANIMATION) {
+    wmKeyMap *keymap;
+
     /* time-markers */
-    wmKeyMap *keymap = WM_keymap_ensure(wm->defaultconf, "Markers", 0, 0);
+    keymap = WM_keymap_ensure(wm->defaultconf, "Markers", 0, 0);
     WM_event_add_keymap_handler_poll(handlers, keymap, event_in_markers_region);
-  }
-  if (flag & ED_KEYMAP_ANIMATION) {
+
+    /* time-scrubbing */
+    keymap = WM_keymap_ensure(wm->defaultconf, "Scrubbing", 0, 0);
+    WM_event_add_keymap_handler_poll(handlers, keymap, event_in_scrubbing_region);
+
     /* frame changing and timeline operators (for time spaces) */
-    wmKeyMap *keymap = WM_keymap_ensure(wm->defaultconf, "Animation", 0, 0);
+    keymap = WM_keymap_ensure(wm->defaultconf, "Animation", 0, 0);
     WM_event_add_keymap_handler(handlers, keymap);
   }
   if (flag & ED_KEYMAP_FRAMES) {