Merge pull request #1899 from matrix-org/dbkr/dbkr/fix_sticker_size_jumping_2

Fix stickers briefly being 2x the size

src/components/views/messages/MStickerBody.js

@@ -107,6 +107,16 @@ export default class MStickerBody extends MImageBody {
             placeholderFixupHeight = content.info.h + 'px';
         }
 
+        // The pixel size of sticker images is generally larger than their intended display
+        // size so they render at native reolution on HiDPI displays. We therefore need to
+        // explicity set the size so they render at the intended size.
+        // XXX: This will be clobberred when we run fixupHeight(), but we need to do it
+        // here otherwise the stickers are momentarily displayed at the pixel size.
+        const imageStyle = {
+            height: content.info.h,
+            // leave the browser the calculate the width automatically
+        };
+
         placeholderSize = placeholderSize + 'px';
 
         // Body 'ref' required by MImageBody
@@ -132,6 +142,7 @@ export default class MStickerBody extends MImageBody {
                     <img
                         className={'mx_MStickerBody_image ' + this.state.imageClasses}
                         src={contentUrl}
+                        style={imageStyle}
                         ref='image'
                         alt={content.body}
                         onLoad={this._onImageLoad}