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, 12 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_space_types.h b/source/blender/makesdna/DNA_space_types.h
index 867da1bcb82..9d9b41a1f81 100644
--- a/source/blender/makesdna/DNA_space_types.h
+++ b/source/blender/makesdna/DNA_space_types.h
@@ -1037,6 +1037,12 @@ enum {
  * \{ */
 
 /* Image/UV Editor */
+
+typedef struct SpaceImageOverlay {
+  int flag;
+  char _pad[4];
+} SpaceImageOverlay;
+
 typedef struct SpaceImage {
   SpaceLink *next, *prev;
   /** Storage of regions for inactive spaces. */
@@ -1096,6 +1102,7 @@ typedef struct SpaceImage {
   int tile_grid_shape[2];
 
   MaskSpaceInfo mask_info;
+  SpaceImageOverlay overlay;
 } SpaceImage;
 
 /* SpaceImage.dt_uv */
@@ -1158,7 +1165,7 @@ typedef enum eSpaceImage_Flag {
   SI_PREVSPACE = (1 << 15),
   SI_FULLWINDOW = (1 << 16),
 
-  SI_FLAG_UNUSED_17 = (1 << 17), /* cleared */
+  SI_FLAG_UNUSED_17 = (1 << 17),
   SI_FLAG_UNUSED_18 = (1 << 18), /* cleared */
 
   /**
@@ -1181,6 +1188,10 @@ typedef enum eSpaceImage_Flag {
   SI_SHOW_B = (1 << 29),
 } eSpaceImage_Flag;
 
+typedef enum eSpaceImageOverlay_Flag {
+  SI_OVERLAY_SHOW_OVERLAYS = (1 << 0),
+} eSpaceImageOverlay_Flag;
+
 /** \} */
 
 /* -------------------------------------------------------------------- */