Fix #126728: Movie Clip Editor "Sync Visible Range" option not working

True for both `Graph` and `Dopesheet` views in the MCE.

For all other time-based editors, the main region (`RGN_TYPE_WINDOW`) is
of interest to be tagged for syncing `V2D_VIEWSYNC_SCREEN_TIME`. In the
case of the Movie Clip Editor however, the `Graph` and `Dopesheet`
regions in question are of type `RGN_TYPE_PREVIEW`.

So to resolve, we have to take this into account in view2d_sync RNA code

NOTE: this PR does not add versioning code, so any "falsely" tagged
`Graph` and `Dopesheet` view will "loose" the setting (will have to be
enabled again on the "right" region), this could be added though -- it
would be impossible to tell **which**  view exactly, so on each
`RGN_TYPE_WINDOW` encountered, we'd have to then tag **both** `Graph`
and `Dopesheet` afaict

Pull Request: https://projects.blender.org/blender/blender/pulls/126785

source/blender/blenkernel/BKE_blender_version.h

@@ -31,7 +31,7 @@ extern "C" {
 
 /* Blender file format version. */
 #define BLENDER_FILE_VERSION BLENDER_VERSION
-#define BLENDER_FILE_SUBVERSION 66
+#define BLENDER_FILE_SUBVERSION 67
 
 /* Minimum Blender version that supports reading file written with the current
  * version. Older Blender versions will test this and cancel loading the file, showing a warning to

source/blender/blenloader/intern/versioning_400.cc

@@ -62,6 +62,7 @@
 #include "BKE_nla.h"
 #include "BKE_node_runtime.hh"
 #include "BKE_scene.hh"
+#include "BKE_screen.hh"
 #include "BKE_tracking.h"
 
 #include "IMB_imbuf_enums.h"
@@ -4329,6 +4330,22 @@ void blo_do_versions_400(FileData *fd, Library * /*lib*/, Main *bmain)
     fix_built_in_curve_attribute_defaults(bmain);
   }
 
+  if (!MAIN_VERSION_FILE_ATLEAST(bmain, 402, 67)) {
+    LISTBASE_FOREACH (bScreen *, screen, &bmain->screens) {
+      LISTBASE_FOREACH (ScrArea *, area, &screen->areabase) {
+        LISTBASE_FOREACH (SpaceLink *, sl, &area->spacedata) {
+          if (sl->spacetype == SPACE_CLIP) {
+            ARegion *region = BKE_area_find_region_type(area, RGN_TYPE_WINDOW);
+            if (region != nullptr) {
+              View2D *v2d = &region->v2d;
+              v2d->flag &= ~V2D_VIEWSYNC_SCREEN_TIME;
+            }
+          }
+        }
+      }
+    }
+  }
+
   /**
    * Always bump subversion in BKE_blender_version.h when adding versioning
    * code here, and wrap it inside a MAIN_VERSION_FILE_ATLEAST check.

source/blender/makesrna/intern/rna_space.cc

@@ -877,7 +877,12 @@ static bool rna_Space_view2d_sync_get(PointerRNA *ptr)
   ARegion *region;
 
   area = rna_area_from_space(ptr); /* can be nullptr */
-  region = BKE_area_find_region_type(area, RGN_TYPE_WINDOW);
+  if (area->spacetype == SPACE_CLIP) {
+    region = BKE_area_find_region_type(area, RGN_TYPE_PREVIEW);
+  }
+  else {
+    region = BKE_area_find_region_type(area, RGN_TYPE_WINDOW);
+  }
   if (region) {
     View2D *v2d = &region->v2d;
     return (v2d->flag & V2D_VIEWSYNC_SCREEN_TIME) != 0;
@@ -900,7 +905,12 @@ static void rna_Space_view2d_sync_set(PointerRNA *ptr, bool value)
     return;
   }
 
-  region = BKE_area_find_region_type(area, RGN_TYPE_WINDOW);
+  if (area->spacetype == SPACE_CLIP) {
+    region = BKE_area_find_region_type(area, RGN_TYPE_PREVIEW);
+  }
+  else {
+    region = BKE_area_find_region_type(area, RGN_TYPE_WINDOW);
+  }
   if (region) {
     View2D *v2d = &region->v2d;
     if (value) {
@@ -918,7 +928,12 @@ static void rna_Space_view2d_sync_update(Main * /*bmain*/, Scene * /*scene*/, Po
   ARegion *region;
 
   area = rna_area_from_space(ptr); /* can be nullptr */
-  region = BKE_area_find_region_type(area, RGN_TYPE_WINDOW);
+  if (area->spacetype == SPACE_CLIP) {
+    region = BKE_area_find_region_type(area, RGN_TYPE_PREVIEW);
+  }
+  else {
+    region = BKE_area_find_region_type(area, RGN_TYPE_WINDOW);
+  }
 
   if (region) {
     bScreen *screen = (bScreen *)ptr->owner_id;