[Webkit-unassigned] [Bug 181709] New: Rendering errors when using CSS transforms (flickering and missing content)

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Tue Jan 16 17:02:24 PST 2018


https://bugs.webkit.org/show_bug.cgi?id=181709

            Bug ID: 181709
           Summary: Rendering errors when using CSS transforms (flickering
                    and missing content)
           Product: WebKit
           Version: Other
          Hardware: All
                OS: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: steffen at deusch.me
                CC: bfulgham at webkit.org, simon.fraser at apple.com,
                    zalan at apple.com

Hello everyone,
this is my first bug report for WebKit, so it's maybe not perfect yet and I'm sorry about that.

I'm posting this based on my issue in the WPEWebKit repo on GitHub: https://github.com/WebPlatformForEmbedded/WPEWebKit/issues/434
As you can read there, I've noticed some strange rendering errors when using CSS transforms to create scrolling effects.
In WPE the content just disappears after scrolling for a while. When there is a repaint (I guess), e.g. because some other element on the page changes, it appears again.
The hardware used for testing this was a Raspberry Pi 3 and a video is available here: https://s3.eu-central-1.amazonaws.com/steffend/public/wpe-test-rpi3/rss-scroller/vid.mp4

First I thought that this is a bug with WPE only, but then I noticed that another example of a scrolling table has a similar issue: https://github.com/WebPlatformForEmbedded/WPEWebKit/issues/434#issuecomment-358153090
While I've got the same "content-disappearing" problem in in WPE, I also noticed flickering issues on Safari 11.0.2, Safari Tech Preview 47, WebKit Nightly and Mobile Safari, as you can see in the attached videos on GitHub.
I'm not quite sure if the flickering issue is connected to the disappearing problem, but sometimes I see some form of the latter one on iOS too, although I couldn't reliably reproduce it.

In Chrome/Chromium these examples all work as expected and as I'm using these techniques in production I'm currently forced to use Chromium based clients instead of e.g. WPE as this is quite a critical issue in my opinion.

Versions:
- all WPE versions I tested, master and stable branches, buildroot and yocto builds
- flickering in all WebKit-based browsers I tested (iOS, macOS)

Thanks for any help,
Steffen Deusch

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