UV/Image Editor: Overlay Popover

The overlay options in the image/uv editor is hidden in side panels and menus. Sometimes this panel is even hidden, while still useful.
The goal of this task is to introduce an overlay pop-over just like the overlay-popover of the 3d viewport.

Popover has
* UV Stretching (only available in the UV mode, when active object mode is a mesh and in OB_EDIT mode)
* Display As (only available in the UV mode, when active object mode is a mesh and in OB_EDIT mode)
* Show Modified (only available in the UV mode, when active object mode is a mesh and in OB_EDIT mode)
* Show UV Edges (including opacity slider; available UV, View, Paint, when active object mode is a mesh and in OB_EDIT mode)
* Udim tiles when no image is available.

Like the 3d viewport, there will be a editor toggle to enable/disable the overlays

For compatibility reasons the RNA properties are added to both the `SpaceImage.uv_editor` amd `SpaceImage.overlay`. On DNA level they are still stored in the SpaceImage. only new properties are added to the SpaceImageOverlay struct. During the next major release we could remove these options from `SpaceImage.uv_editor`. This should be noted in the Python section of release notes.

Reviewed By: Julian Eisel, Pablo Vazquez

Differential Revision: https://developer.blender.org/D8890

1 files changed, 14 insertions, 0 deletions

diff --git a/source/blender/blenloader/intern/versioning_290.c b/source/blender/blenloader/intern/versioning_290.c
index b9153307d70..520a5da878c 100644
--- a/source/blender/blenloader/intern/versioning_290.c
+++ b/source/blender/blenloader/intern/versioning_290.c
@@ -806,5 +806,19 @@ void blo_do_versions_290(FileData *fd, Library *UNUSED(lib), Main *bmain)
         }
       }
     }
+
+    /* UV/Image show overlay option. */
+    if (!DNA_struct_find(fd->filesdna, "SpaceImageOverlay")) {
+      LISTBASE_FOREACH (bScreen *, screen, &bmain->screens) {
+        LISTBASE_FOREACH (ScrArea *, area, &screen->areabase) {
+          LISTBASE_FOREACH (SpaceLink *, space, &area->spacedata) {
+            if (space->spacetype == SPACE_IMAGE) {
+              SpaceImage *sima = (SpaceImage *)space;
+              sima->overlay.flag = SI_OVERLAY_SHOW_OVERLAYS;
+            }
+          }
+        }
+      }
+    }
   }
 }