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, 7 insertions, 4 deletions

diff --git a/source/blender/draw/intern/draw_view.c b/source/blender/draw/intern/draw_view.c
index 86f19c6cfd7..1f1b52e9577 100644
--- a/source/blender/draw/intern/draw_view.c
+++ b/source/blender/draw/intern/draw_view.c
@@ -208,11 +208,14 @@ static bool is_cursor_visible_2d(const DRWContextState *draw_ctx)
   if (space_data == NULL) {
     return false;
   }
-  if (space_data->spacetype == SPACE_IMAGE) {
-    SpaceImage *sima = (SpaceImage *)draw_ctx->space_data;
-    return sima->mode == SI_MODE_UV;
+  if (space_data->spacetype != SPACE_IMAGE) {
+    return false;
+  }
+  SpaceImage *sima = (SpaceImage *)space_data;
+  if (sima->mode != SI_MODE_UV) {
+    return false;
   }
-  return false;
+  return (sima->overlay.flag & SI_OVERLAY_SHOW_OVERLAYS) != 0;
 }
 
 void DRW_draw_cursor_2d(void)