Bug 242312 – requestAnimationFrame is not called after a certain WKWebView magnification

• Component: Animations
• Status: NEW

[Felix Franz]

Created attachment 460651 [details]
Xcode project showing the issue

In our application (MacOS-application using WKWebView), we have an issue where after a certain magnification requestAnimationFrame-handlers are not called anymore (or very very rarely). 

I tried to strip down the issue and was able to reproduce it in a simple Cocoa-Application using a WKWebView which displays a web page. 

Steps to reproduce:

* build and open the attached Xcode project
* you see some elements and a red cell with an updating number in it 
* Click on the "zoom in"-button (and make sure you see the updating number)
* Starting from a magnification of 3 (you can see the magnification in the lower right corner) the number stops updating
* zoom out again and it starts again. 


the requestAnimationFrame handler is set in the viewer.html. If I use a simpler web page (only a one html with the same, or using a iframe it works as expected).

[Radar WebKit Bug Importer]

<rdar://problem/96447352>

[Smoley]

Thanks for filing, this does not reproduce for me on macOS 12.5 beta 5 (21G5063a). I stopped zooming in around 25. Are you able to reproduce this on that build?

[Simon Fraser (smfr)]

I can reproduce. You have to scroll sideways a little to get into the state where it stops animating.

[Simon Fraser (smfr)]

The visibleRect passed to `FrameView::updateScriptedAnimationsAndTimersThrottlingState` is wrong.

We should just change this code to use an internal IntersectionObserver.