Bug 49436

Summary: [G33 SNA] Rendering corruptions in Firefox with CSS3 element transformations
Product: xorg Reporter: Matti Hämäläinen <ccr>
Component: Driver/intelAssignee: Chris Wilson <chris>
Status: RESOLVED FIXED QA Contact: Xorg Project Team <xorg-team>
Severity: normal    
Priority: medium    
Version: unspecified   
Hardware: x86 (IA32)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:

Description Matti Hämäläinen 2012-05-03 09:37:20 UTC 
Interesting rendering corruptions can occur when using CSS3 element transformations in Firefox. This can be demonstrated using FF10+ or later at least: http://tnsp.org/~ccr/intel-gfx/test.html

A screen capture video in Theora/OGV format: http://tnsp.org/~ccr/intel-gfx/sna-g33-css-trans.ogv

It would seem that Opera does not suffer from this same problem, but I think this is because it most likely(?) uses its own software rendering whereas FF relies on Cairo and through that on acceleration.

-- Window manager: WindowMaker 0.92 (also present with Compiz, so probably not
WM related)
-- chipset: 00:02.0 VGA compatible controller: Intel Corporation 82G33/G31
Express Integrated Graphics Controller (rev 10)
-- system architecture: i686 / 32bit
-- xf86-video-intel: GIT f4c34e9ab32f31669896b8f626195827a85af337
-- xserver: X.Org X Server 1.12.1 from Debian unstable
-- mesa: 8.0.2-2 from Debian unstable
-- libpixman: 0.25.2-1
-- libdrm version: 2.4.33-1
-- kernel version: 3.3.4 (vanilla from kernel.org)
-- Linux distribution: Debian Testing aka Wheezy
-- Machine or mobo model: Asus P5KPL-CM
-- Display connector: VGA
Comment 1 Chris Wilson 2012-05-03 09:41:44 UTC 
Indeed, I've narrowed down the (last) bug to rendering to an element that is larger than can be natively handled by the GPU.
Comment 2 Chris Wilson 2012-05-03 11:49:08 UTC 
To be even more precise, it is the handling of a trapezoid through a tiled mask that appears to be the source of the error. Closer...
Comment 3 Chris Wilson 2012-05-03 14:35:57 UTC 
Oh that was fun.

All the commits leading up to

commit 61cac5c265279d45677262216a0ba56f548cd898
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Thu May 3 22:33:59 2012 +0100

    sna: Maintain a reference to the chain of proxies
    
    Rather than attempt to flatten the chain to the last link, we may need
    to hold a reference to the intermediate links in case of batch buffer
    submission.
    
    Fixes http://tnsp.org/~ccr/intel-gfx/test.html
    
    Reported-by: Matti Hamalainen <ccr@tnsp.org>
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=49436
    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

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