zoomed in blurred text shadows generate garbage bounding box fragments

[Gankra]

Try zooming in and out on this page:

data:text/html,<meta charset="utf-8"><span style="text-shadow: 2px 2px 1px red"><div>Blur<span style="color: blue">%F0%9F%8E%89</span><span style="color: rgba(0,0,0,0.7)">%F0%9F%8E%89</span><span style="color: rgba(0,0,255,0.4)">%F0%9F%8E%89</span><span style="color: transparent">%F0%9F%8E%89</span><span style="text-shadow: 2px 2px 2px red"></span></div><div>Blur<span style="color: blue">A</span><span style="color: rgba(0,0,0,0.7)">A</span><span style="color: rgba(0,0,255,0.4)">A</span><span style="color: transparent">A</span></div></span>

[Gankra]

Can't repro on windows.

[Gankra]

Note the example is extra complicated just to make it easier to see, and to rule out some things. This also demonstrates the issue:

<span style="color: transparent; text-shadow: 0px 0px 1px black">A</span>

[Gankra]

In theory this makes reftests/text/shadow-single.yaml sufficient to demonstrate the issue but it seems like zoom is somehow relevant, and wrench can't do it.

[Gankra]

Actually hmm I can see this on some unzoomed characters sometimes?

[Gankra]

Or not? Seems like reset-zoom was just acting janky?

[Gankra]

Ok I spent some more time on this, and I've reproduced it on linux, macos, and windows. I wasn't seeing it initially on windows or wrench because it appears to be based on global effects on the glyph cache: you need to launch a few tabs to social media sites first and then load the example and it will work. I was able to reproduce this in a binary recording in wrench as well, although if you export any one frame as a yaml it won't reproduce the issue!

[Gankra]

I have shown @kvark how to reproduce this locally, hopefully they can figure this out >.>

[glennw]

@kvark Possibly a good use case for your new capturing WIP ? :)

[kvark]

@glennw ^_^ exactly what I was telling @gankro :)
This needs built-frame level of capturing, which is still to implement. I'll try to make this happen after the pending PRs are done.

[glennw]

I was unable to reproduce this on Linux - either via Gecko or replaying the recording in wrench. Might only appear on mac?

[Gankra]

Confirmed that I can't reproduce this on firefox nightly anymore (macos).