Merge pull request #4555 from vector-im/doug/4552_fix_attachment_view_mask

Fix image and video thumbnail masks on cell reuse.

CHANGES.rst

@@ -18,6 +18,7 @@ Changes to be released in next version
  * it's easy for the back button to trigger a leftpanel reveal (#4438).
  * Show / hide reset button in secrets recovery screen (#4546).
  * Share Extension: Fix layout when searching (#4258).
+ * Timeline: Fix incorrect crop of media thumbnails (#4552).
 
 ⚠️ API Changes
  * 

Riot/Modules/Room/DataSources/RoomDataSource.m

@@ -1039,12 +1039,10 @@ const CGFloat kTypingCellHeight = 24;
 
 - (void)applyMaskToAttachmentViewOfBubbleCell:(MXKRoomBubbleTableViewCell *)cell
 {
-    if (cell.attachmentView && !cell.attachmentView.layer.mask)
+    if (cell.attachmentView)
     {
-        UIBezierPath *myClippingPath = [UIBezierPath bezierPathWithRoundedRect:cell.attachmentView.bounds cornerRadius:6];
-        CAShapeLayer *mask = [CAShapeLayer layer];
-        mask.path = myClippingPath.CGPath;
-        cell.attachmentView.layer.mask = mask;
+        cell.attachmentView.layer.cornerRadius = 6;
+        cell.attachmentView.layer.masksToBounds = YES;
     }
 }