Bug 65030 – Avoiding painting backgrounds if they are fully obscures by an object's foreground

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[Simon Fraser (smfr)]

We shouldn't waste time painting backgrounds for things like images, for which it's easy to determine that the foreground fully obscures that background. This helps particularly in cases where the background might contain an animated "loading" image; that currently causes continual repaints, and it should not.

[Simon Fraser (smfr)]

This is only going to work for JPEG initially: bug 65033.

[Simon Fraser (smfr)]

Created attachment 101774 [details]
Patch

Comment on attachment 101774 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=101774&action=review

> Source/WebCore/ChangeLog:8
> +        Some pages used animated loading GIFs as the background of <img>,

Confused by the use of “used” in the past tense.

> Source/WebCore/rendering/RenderImage.cpp:411
> +    if (!image->isBitmapImage())

I think you need to null-check image.

[Simon Fraser (smfr)]

http://trac.webkit.org/changeset/91628

[Ryosuke Niwa]

This patch seems to have caused a crash on Chromium Linux:
http://build.webkit.org/results/Chromium%20Linux%20Release%20(Tests)/r91628%20(21410)/results.html
http://build.webkit.org/results/Chromium%20Linux%20Release%20(Flexbox)/r91628%20(1508)/results.html

Given these are two different bots, I highly doubt that this is a flake.  Unfortunately, these are release builds so we can't get stack trace out of them.

There's also one failing test on Chromium Mac:
http://build.webkit.org/results/Chromium%20Mac%20Release%20(Tests)/r91628%20(9716)/results.html

But I'm not certain if this is a real regression or just a flakiness.

[Simon Fraser (smfr)]

Do we have any more information on whether those crashes persisted?

[Ryosuke Niwa]

(In reply to comment #6)
> Do we have any more information on whether those crashes persisted?

They have been crashing quite consistently: http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=fast%2Fcanvas%2Fwebgl%2Fdrawingbuffer-test.html%2Cfast%2Fcanvas%2Fcanvas-bg-multiple-removal.html%2Cfast%2Fcanvas%2Fcanvas-as-image-incremental-repaint.html

[Simon Fraser (smfr)]

Odd that it's just Linux that's crashing.

[Ryosuke Niwa]

(In reply to comment #8)
> Odd that it's just Linux that's crashing.

It's possible that there's a cr-linux or skia bug; or that only cr-linux hit some specific timing.

[Simon Fraser (smfr)]

Let's continue discussing the crashes in bug 65063.