Fix T84053: Mask overlay in image editor not working

The mask overlay wasn't part of the overlay engine. The reasoning nehind
this was that more editors used the mask overlay and most of them used
old drawing code. This patch adds the mask overlay drawing to the draw
overlay engine. This code path will only be used by the image editor
VSE, Compositor and Movie Clip editor will still use the previous
method.

During this patch some alternatives have been researched:
1. `ED_mask_draw_region`: this would lead to different code paths when
   drawing in the image editor, and some hacks to retrieve the correct
   framebuffer.
2. Add mask drawing to image engine: Would lead to incorrect color
   management when viewing the mask.
3. Add mask drawing to image engine and overlay engine: Would lead to
   duplicated code.
4. Add mask drawing to overlay engine and for combined overlay select
   the correct framebuffer.

Option 4 was chosen as the exception (switching framebuffers) can be
done without hacks. The code stays clean.

1 files changed, 18 insertions, 2 deletions

diff --git a/source/blender/draw/engines/overlay/overlay_shader.c b/source/blender/draw/engines/overlay/overlay_shader.c
index f3840679d80..88f4e28c039 100644
--- a/source/blender/draw/engines/overlay/overlay_shader.c
+++ b/source/blender/draw/engines/overlay/overlay_shader.c
@@ -78,7 +78,7 @@ extern char datatoc_edit_uv_edges_frag_glsl[];
 extern char datatoc_edit_uv_faces_vert_glsl[];
 extern char datatoc_edit_uv_face_dots_vert_glsl[];
 extern char datatoc_edit_uv_stretching_vert_glsl[];
-extern char datatoc_edit_uv_stencil_image_vert_glsl[];
+extern char datatoc_edit_uv_image_vert_glsl[];
 extern char datatoc_edit_uv_tiled_image_borders_vert_glsl[];
 extern char datatoc_extra_frag_glsl[];
 extern char datatoc_extra_vert_glsl[];
@@ -94,6 +94,7 @@ extern char datatoc_facing_vert_glsl[];
 extern char datatoc_grid_frag_glsl[];
 extern char datatoc_grid_vert_glsl[];
 extern char datatoc_image_frag_glsl[];
+extern char datatoc_edit_uv_image_mask_frag_glsl[];
 extern char datatoc_image_vert_glsl[];
 extern char datatoc_motion_path_line_vert_glsl[];
 extern char datatoc_motion_path_line_geom_glsl[];
@@ -185,6 +186,7 @@ typedef struct OVERLAY_Shaders {
   GPUShader *edit_uv_stretching_area;
   GPUShader *edit_uv_tiled_image_borders;
   GPUShader *edit_uv_stencil_image;
+  GPUShader *edit_uv_mask_image;
   GPUShader *extra;
   GPUShader *extra_select;
   GPUShader *extra_groundline;
@@ -1070,11 +1072,25 @@ GPUShader *OVERLAY_shader_edit_uv_stencil_image(void)
   OVERLAY_Shaders *sh_data = &e_data.sh_data[0];
   if (!sh_data->edit_uv_stencil_image) {
     sh_data->edit_uv_stencil_image = DRW_shader_create_with_shaderlib(
-        datatoc_edit_uv_stencil_image_vert_glsl, NULL, datatoc_image_frag_glsl, e_data.lib, NULL);
+        datatoc_edit_uv_image_vert_glsl, NULL, datatoc_image_frag_glsl, e_data.lib, NULL);
   }
   return sh_data->edit_uv_stencil_image;
 }
 
+GPUShader *OVERLAY_shader_edit_uv_mask_image(void)
+{
+  OVERLAY_Shaders *sh_data = &e_data.sh_data[0];
+  if (!sh_data->edit_uv_mask_image) {
+    sh_data->edit_uv_mask_image = DRW_shader_create_with_shaderlib(
+        datatoc_edit_uv_image_vert_glsl,
+        NULL,
+        datatoc_edit_uv_image_mask_frag_glsl,
+        e_data.lib,
+        NULL);
+  }
+  return sh_data->edit_uv_mask_image;
+}
+
 GPUShader *OVERLAY_shader_image(void)
 {
   const DRWContextState *draw_ctx = DRW_context_state_get();