Fix T95338: missing image editor refresh after render compositing

This was an old issue, but recent image partial update changes made this more
likely to happen in some cases. Now ensure that whenever the rendered scene
switches the image is updated.

source/blender/editors/render/render_internal.cc

@@ -634,6 +634,12 @@ static void image_rect_update(void *rjv, RenderResult *rr, volatile rcti *renrec
 static void current_scene_update(void *rjv, Scene *scene)
 {
   RenderJob *rj = static_cast<RenderJob *>(rjv);
+
+  if (rj->current_scene != scene) {
+    /* Image must be updated when rendered scene changes. */
+    BKE_image_partial_update_mark_full_update(rj->image);
+  }
+
   rj->current_scene = scene;
   rj->iuser.scene = scene;
 }

source/blender/render/intern/pipeline.c

@@ -1122,6 +1122,8 @@ static void do_render_compositor_scenes(Render *re)
     return;
   }
 
+  bool changed_scene = false;
+
   /* now foreach render-result node we do a full render */
   /* results are stored in a way compositor will find it */
   GSet *scenes_rendered = BLI_gset_ptr_new(__func__);
@@ -1134,11 +1136,20 @@ static void do_render_compositor_scenes(Render *re)
           do_render_compositor_scene(re, scene, cfra);
           BLI_gset_add(scenes_rendered, scene);
           node->typeinfo->updatefunc(restore_scene->nodetree, node);
+
+          if (scene != re->scene) {
+            changed_scene = true;
+          }
         }
       }
     }
   }
   BLI_gset_free(scenes_rendered, NULL);
+
+  if (changed_scene) {
+    /* If rendered another scene, switch back to the current scene with compositing nodes. */
+    re->current_scene_update(re->suh, re->scene);
+  }
 }
 
 /* bad call... need to think over proper method still */