[mac] REGRESSION (r122215): Animated GIF outside the viewport doesn't play when scrolled into view

[Tim Horton]

Steps to Reproduce:

1. On Mountain Lion, with the Mac port (where tiled scrolling is enabled):
2. With a relatively small window:
3. Load http://whenapthuntinginsf.tumblr.com.
4. Scroll down.

Expected: All of the GIFs animate.

Actual: The GIFs which are scrolled into view do not animate.

This is probably due to the fact that they are offscreen (on offscreen tiles) when they are first painted, so they don't animate. Then, when they are scrolled into view, they don't need to repaint, so they don't realize they should start animating.

This will probably require some special logic in the tiled scrolling case.

<rdar://problem/12067641>

[Tim Horton]

This regressed in http://trac.webkit.org/changeset/122215. The ChangeLog entry for that patch includes the comment: "This patch makes GIF animation outside the viewport be paused."

[Dongseong Hwang]

(In reply to comment #1)
> This regressed in http://trac.webkit.org/changeset/122215. The ChangeLog entry for that patch includes the comment: "This patch makes GIF animation outside the viewport be paused."

I'm sorry for this regression.

I think the tiled scrolling disables RenderObject::willRenderImage from checking if the renderer is outside the viewport. "viewRect().intersects(absoluteClippedOverflowRect())" is often used in WebKit, such as spatial navigation.
I think the tiled scrolling should return the proper value.

bool RenderObject::willRenderImage(CachedImage*)
{
    ....
    // If a renderer is outside the viewport, we won't render.
    return viewRect().intersects(absoluteClippedOverflowRect());
}

[Dongseong Hwang]

Created attachment 167425 [details]
Patch

[Dongseong Hwang]

(In reply to comment #3)
> Created an attachment (id=167425) [details]
> Patch

Rollback previous patch because this patch caused two problems.
1. GIF animation is occasionally paused when tiled scrolling is enabled.
2. This change regressed Apple's Membuster benchmark by ~20% (80MB.)

[WebKit Review Bot]

Comment on attachment 167425 [details]
Patch

Clearing flags on attachment: 167425

Committed r130573: <http://trac.webkit.org/changeset/130573>

[WebKit Review Bot]

All reviewed patches have been landed.  Closing bug.