Bug 230751 – REGRESSION (Safari 15): Protomaps is very slow/hangy in Safari (large paths?)

• Status: RESOLVED
• Resolution: DUPLICATE
• Component: Canvas

[Simon Fraser (smfr)]

https://protomaps.github.io/protomaps.js/examples/leaflet.html#11/35.6079/139.7458 is very slow, to the point of hanging.

Seems like a canvas/GPU process thing.

[Radar WebKit Bug Importer]

<rdar://problem/83497019>

[Brandon Liu]

Hi, library author here. To describe what I'm seeing: On Safari 15 on macOS Big Sur, Technology Preview, and iOS 15 Safari, the tab will either crash or the UI thread will hang randomly after panning/zooming for a while, sometimes immediately on page load.

I can confirm that turning off “GPU Process: Canvas Rendering” fixes the problem, but that isn't a viable workaround for users.

From experimenting with the Canvas calls in the library it seems to be related to rasterizing a path (context.fill(), context.stroke()) with hundreds to thousands of vertices.

Similar bug reports:

1. https://developer.apple.com/forums/thread/685866
2. https://github.com/ant-design/ant-design-charts/issues/855
3. https://github.com/flutter/flutter/issues/89655

[Simon Fraser (smfr)]

Thanks for the update, we're tracking this regression.

[Brandon Liu]

As an update, I'm pretty sure the root cause here is the same at https://bugs.webkit.org/show_bug.cgi?id=231157 .

I've implemented a workaround for the library to limit the # of vertices in a single call to stroke() or fill(). It's been successful so far on the devices I've tested, will report back after more testing.

[Cameron McCormack (:heycam)]

Brandon, is the workaround already present in the URL Simon linked in comment 0?  Testing with that URL I couldn't reproduce the hanging.

If so, then we should probably just dupe this bug to the long path issue in bug 231157.

[Brandon Liu]

Cameron,

There is a partial workaround implemented on that page which makes it more difficult to reproduce, but the crash/hang is still present; I do believe the root cause is the same, so you can mark this as a dupe.

Brandon

[Cameron McCormack (:heycam)]

Thanks for confirming.

*** This bug has been marked as a duplicate of bug 231157 ***