Merge branch 'blender-v4.0-release'

source/blender/blenkernel/intern/image.cc

@@ -4385,6 +4385,24 @@ static ImBuf *image_get_render_result(Image *ima, ImageUser *iuser, void **r_loc
     }
   }
 
+  /* Put an empty image buffer to the cache so that the Image.has_data detects that some data
+   * has been loaded for this Image data-block.
+   *
+   * Surely there are all the design questions about scene-dependent Render Result image datablock,
+   * and the behavior of the flag dependent on wheter the Render Result image was ever shown on
+   * screen. The purpose of this code is to preserve the Python API behavior to the level prior to
+   * the RenderResult refactor to use ImBuf which happened for Blender 4.0. */
+  if (ima->cache == nullptr) {
+    ImBuf *empty_ibuf = IMB_allocImBuf(0, 0, 0, 0);
+    image_assign_ibuf(ima, empty_ibuf, IMA_NO_INDEX, 0);
+
+    /* The cache references the image buffer, and the freeing only happens if the buffer has 0
+     * references at the time when the IMB_freeImBuf() is called. This particular image buffer is
+     * to be freed together with the cache, without any extra reference counting done by any image
+     * pixel accessor. */
+    IMB_freeImBuf(empty_ibuf);
+  }
+
   if (pass_ibuf) {
     /* TODO(sergey): Perhaps its better to assign dither when ImBuf is allocated for the render
      * result. It will avoid modification here, and allow comparing render results with different