1422567 - Crazy subreddit CSS with hundreds of text shadows is slow in WebRender

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect, P3)

Description

[Thomas Daede [:TD-Linux]]

Minimized testcase here: https://codepen.io/anon/pen/YEBLVy

Runs at ~15fps on my machine.

Comment 1

[Thomas Daede [:TD-Linux]]

Apparently this is a hack to work around text-shadow not having a way to grow the outline other than blur (or alternately, no way to control the shape of the blur falloff). Here's another example of it in action, for a different use: https://eager.io/blog/smarter-link-underlines/

Comment 2

[Milan Sreckovic [:milan] (needinfo for best results)]

What's the Firefox performance without WebRender enabled?

Comment 3

[Thomas Daede [:TD-Linux]]

It's OK without WebRender - not because rendering is fast (it's even slower than with WebRender) but because scrolling and the animated css background don't cause repaints in that area of the page. (the linked page only reaches 30fps without WebRender because the animated header actually causes continuous repaints, just not to the region with the css shadows)

Comment 4

[Thomas Daede [:TD-Linux]]

Found another example in the wild, with an even greater hit (runs at ~5fps when the text is in view) https://twofold.salty-salty-studios.com/

Comment 5

[Jeff Muizelaar [:jrmuizel]]

This seems to run ok for me on Windows Nvidia. Is it still a problem for you? What hardware?

Comment 6

[Jeff Muizelaar [:jrmuizel]]

Actually running it at a higher resolution really slows things down.

Comment 7

[mitchell]

Can confirm (Nvidia GTX 970 on Windows 10 x64), latest nightly, on a 4k monitor. Performance on text-shadow heavy pages is abominable.

The bottom of the following page is particularily bad: https://system-admin-girl.com/ (beware, anime)

Moving the firefox window to a 1080p monitor improves performance significantly, though there are still noticable jitters when beginning a scroll.

Comment 8

[Glenn Watson [:gw]]

With picture caching enabled by default, this is running at a smooth 60 fps @ 4k on my Intel HD4600, so I think we can close this.

Comment 9

[mitchell]

Can confirm, performance is perfect on the above testcases. Thanks all!