Bug 107547

Summary:

[Qt] Box shadows on a transparency layer is very slow

Product:

WebKit

Reporter:

Allan Sandfeld Jensen <allan.jensen>

Component:

Layout and Rendering

Assignee:

Allan Sandfeld Jensen <allan.jensen>

Status:

RESOLVED FIXED

Severity:

Normal

CC:

noam, nowrep, webkit.review.bot

Priority:

Version:

528+ (Nightly build)

Hardware:

Unspecified

OS:

Unspecified

Bug Depends on:

107549

Bug Blocks:

88186, 103747

Attachments:

Description	Flags
Patch	none
Patch	none

Description Allan Sandfeld Jensen 2013-01-22 03:59:12 PST

If box shadows are applied on top of a transparency layer, the result is very slow painting. An example is the page http://paste.chakra-project.org/3755/.

The issue is that the ShadowBlur layer ends up being the entire size of box element, instead of just the size of the transparency layer. This happens because the clipping set on QPainter is much larger than the area QPainter is painting to. One way to avoid it, is to set an initial clipping to the area QPainter is painting to, so that later clipping (set by intersection), can not end up larger than the layer.

Comment 1 Allan Sandfeld Jensen 2013-01-22 04:01:36 PST

Created attachment 183958 [details]
Patch

Comment 2 David Rosca 2013-01-22 04:23:56 PST

I can confirm that the patch helps the issue. Unfortunately, it's not ideal.
Rendering the page provided changed from unusably slow to slow on my machine (i5).

Comment 3 Allan Sandfeld Jensen 2013-01-22 04:40:18 PST

Committed r140412: <http://trac.webkit.org/changeset/140412>

Comment 4 Allan Sandfeld Jensen 2013-01-22 05:54:49 PST

Created attachment 183976 [details]
Patch

Do not change clips used by QPainter, instead ensure clipBounds return a clip intersected with the window bounds

Comment 5 WebKit Review Bot 2013-01-31 06:09:33 PST

Comment on attachment 183976 [details]
Patch

Clearing flags on attachment: 183976

Committed r141413: <http://trac.webkit.org/changeset/141413>

Comment 6 WebKit Review Bot 2013-01-31 06:09:37 PST

All reviewed patches have been landed.  Closing bug.