[Webkit-unassigned] [Bug 234913] New: Safari iOS stops rendering after switching away and back when using RobotoBold Font

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Thu Jan 6 00:41:31 PST 2022


            Bug ID: 234913
           Summary: Safari iOS stops rendering after switching away and
                    back when using RobotoBold Font
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Canvas
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: gman at chromium.org
                CC: dino at apple.com

Created attachment 448469

  --> https://bugs.webkit.org/attachment.cgi?id=448469&action=review

repo for issue above

Steps to repo

1) Download the zip file, unzip, serve the file (npx servez), open test.html in Safari on iOS (http://<your-mac-ip-address>:8080/test.html)
2) Switch from Safari to the home screen, wait a few seconds
3) Switch back to Safari

What should happen:

you should see some text "Hello World" and "Round 1" animating as well as a count counting up

What happens instead:

No animation happens

Here's a video of it happening ( https://www.youtube.com/watch?v=FftyV0iYtJw ) Notice after going back to Safari the counter is no longer updating

If you go change line 115 from "RobotoBold" to "monospace" and follow the steps above (kill the tab first), you'll see with "monospace" the animation does not stop.

HEre's a video of it working with "monospace" ( https://www.youtube.com/watch?v=g8rKxxayZHw ). notice after going back to Safari the counter is still updating

The sample uses `setInterval` (yea, I know, it should use rAF, the code that provoked this is probably > 10 year old)

If you use the remote debugger, after restoring safari, and put a breakpoint on `draw` you'll see it only gets called once every several seconds and though it is calling drawing functions none of them are affecting the canvas. Further, often you can't even refresh the tab in Safari. You can kill the tab and start a new one though.

My understanding is this worked on iOS 14 (don't have iOS 14 to test but the person that found the bug originally said their site broke when they upgraded to iOS 15). This is the small repo.

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