Bug 139528 – Image animation is not always stopped if used as background-image of a div that is outside viewport

• Component: Layout and Rendering
• Status: RESOLVED INVALID

[Chris Dumez]

Image animation is not always stopped if used as background-image of a div that is outside viewport. In particular, the animation is not stopped if the div has content overflowing *inside* the viewport (even though the animated gif is not visible, only the overflowing content is). This is because shouldRepaintForImageAnimation() relies on the renderer's overflow rect instead of its bounding box to determine if it is inside viewport.

[Chris Dumez]

Created attachment 243098 [details]
Patch

[Chris Dumez]

Created attachment 243103 [details]
Patch

[Chris Dumez]

Created attachment 243104 [details]
Patch

[Chris Dumez]

I regressed this in http://trac.webkit.org/changeset/176212 when refactoring the code to detect if we're inside viewport to be shared between animated images and DOM Timer throttling.

[Simon Fraser (smfr)]

Comment on attachment 243104 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=243104&action=review

> Source/WebCore/rendering/RenderElement.cpp:1371
> +    LayoutRect backgroundPaintingRect = backgroundIsPaintedByRoot ? renderer.view().backgroundRect(&renderer.view()) : renderer.absoluteBoundingBoxRect();

But doesn't this regress the reflection case, and possibly others?

[Chris Dumez]

Comment on attachment 243104 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=243104&action=review

>> Source/WebCore/rendering/RenderElement.cpp:1371
>> +    LayoutRect backgroundPaintingRect = backgroundIsPaintedByRoot ? renderer.view().backgroundRect(&renderer.view()) : renderer.absoluteBoundingBoxRect();
> 
> But doesn't this regress the reflection case, and possibly others?

Hmm, I will have to check. It is indeed possible. If so, it is better to be conservative and use the overflow rect.