Created attachment 466703 [details] A web page to reproduce this issue Layer-backed GIF images may animate improperly or flicker. See the attached page and screen recording for this issue, the GIF image with rabbit ears animates in a wrong frame rate and may even flicker. This issue: * happens only on Intel-based machines running macOS 14 beta. * happens only when the layer's backing store is small enough so that `ImageBufferShareableMappedIOSurfaceBitmapBackend` is used. (Introduced in: https://commits.webkit.org/264004@main.) * happens when WebKit is built with both macOS 13 & 14 SDK. I'm not sure if issue is WebKit specific or it's a CoreGraphics issue.
Created attachment 466704 [details] The screen recording for this issue
<rdar://problem/111161156>
This issue could still be reproduced in macOS 14.0 Developer Beta 2 (23A5276g).