Bug 78943

Summary:	Avoid compositing empty elements
Product:	WebKit	Reporter:	Xianzhu Wang <wangxianzhu>
Component:	Layout and Rendering	Assignee:	Xianzhu Wang <wangxianzhu>
Status:	RESOLVED DUPLICATE
Severity:	Normal	CC:	enne, jamesr, klobag, simon.fraser, vangelis, wiltzius
Priority:	P2
Version:	528+ (Nightly build)
Hardware:	Unspecified
OS:	Unspecified

Description Xianzhu Wang 2012-02-17 16:20:32 PST

Google+ has a zero-height fixed-position element beneath the main content.
we enable compositing for fixed-position elements, which means lots of content divs
overlap it and are also composited.  -- husky@chromium.org

Comment 1 Xianzhu Wang 2012-02-23 11:15:45 PST

Just verified that the patch of bug 78186 also fixed this bug, because an empty rect doesn't intersect any other rect.

Comment 2 Xianzhu Wang 2012-02-23 15:59:46 PST

Sorry my previous verification was not complete. Bug 78186 can prevents empty fixed position element that is at the bottom layer from being composited (and in turn may prevent elements over it from being composited).

If an empty element is over another composited element, it may still be composited because the intersect condition change in bug 34065. Would it be better to fix issue of cliprect cache instead of changing the overlap checking for bug 34065 that will cause unnecessary compositing layers?

We also tried to disable cliprect cache, and didn't see visible performance change.

Comment 3 Xianzhu Wang 2012-03-14 14:32:46 PDT


*** This bug has been marked as a duplicate of bug 63499 ***