http://bugs.freedesktop.org/show_bug.cgi?id=19169
Summary: Tearing at top with multiple opengl windows on intel
hardware
Product: DRI
Version: XOrg CVS
Platform: x86 (IA32)
OS/Version: Linux (All)
Status: NEW
Severity: normal
Priority: medium
Component: General
AssignedTo: [email protected]
ReportedBy: [email protected]
Created an attachment (id=21287)
--> (http://bugs.freedesktop.org/attachment.cgi?id=21287)
Patch to glxgears that adds a teartest.
While one opengl window, rendering less than the capacity of the graphics
hardware, is synchronised to the vertical refresh, once two windows or more are
opened, tearing is apparent at the top of the window, especially if it is
placed near the top of the screen.
While the mesa demo program glsync may be used to investigate this problem, it
doesn't quite highlight it enough because glsync creates too low a graphics
load. I have attached a patch to glxgears that causes alternating vertical
sidebars to be drawn, if a "-teartest" option is set. So running the following
commands together with a patched glxgears:
$ glxgears -geometry 600x600+0+0 -teartest > /dev/null 2>&1 &
$ glxgears -geometry 600x600+600+0 -teartest > /dev/null 2>&1 &
will usually demonstrate the problem. (The graphics must load the system enough
so that the rendering of one of the windows exceeds the vertical blank time,
the time that no display occurs.)
This has been observed on ICH7 and ICH9 with pci ids 8086:2a42 and 8086:27a6,
with the latest tip (as of 18 December 2008)
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