Merge pull request #6454 from SimonBrandner/feature/image-view-load-anim/18186

* Give lightbox a background load animation
* Extends IMediaEventContent by thumbnail info
* Give image view panel a loading animation
* Initial implementation of loading animation
* Take panel height into account
* Update animation speed
* Add some null guards
* Fix animation issues
* Move animations into _animations
* Where does that magic number come from?
* Remove awaiting setState()
* Use CSS var in JS
* Handle prefers-reduced-motion
* More prefers-reduced-motion friendliness

Signed-off-by: Šimon Brandner <simon.bra.ag@gmail.com>

src/components/views/messages/MImageBody.tsx

@@ -117,6 +117,17 @@ export default class MImageBody extends React.Component<IBodyProps, IState> {
                 params.fileSize = content.info.size;
             }
 
+            if (this.image.current) {
+                const clientRect = this.image.current.getBoundingClientRect();
+
+                params.thumbnailInfo = {
+                    width: clientRect.width,
+                    height: clientRect.height,
+                    positionX: clientRect.x,
+                    positionY: clientRect.y,
+                };
+            }
+
             Modal.createDialog(ImageView, params, "mx_Dialog_lightbox", null, true);
         }
     };