[Qt-interest] BLEND_SOURCE_OVER_ARGB32_SSE2 (used to) crash [SOLVED in Qt 4.7.1] - example app: Screenie

[Oliver.Knoll at comit.ch]

On 2010-11-20 Zeljko Zeljko wrote:

>> ...
>> And indeed, "Screenie" works as expected again with Qt 4.7.1 - in case
>> someone else stumbles across the same issue ;)
> 
> No it's not fixed yet (haven't tried distro packaged 4.7.1, but from
> fedora koji packages 4.7.0-8 which merged some patches from 4.7.1 it
> still crashes).

So how can you say "it is not fixed yet [in 4.7.1]" if you tried a distro-Qt which "merged some patches from 4.7.1"? "Some" != "All" ;)

> I've opened this issue at kde bug tracker as I can
> reproduce it only with oxygen theme and kde 4.5.XX with qt-4.7. However,
> kde-4.5.3 with qt-4.6.3 works fine.Default qt styles works as expected
> (plastique,motif,gtk ...etc). Running app with -graphicssystem raster
> doesn't crash. Here is gdb stacktrace
> https://bugs.kde.org/show_bug.cgi?id=254889

Are we talking about the same app "Screenie" (https://code.google.com/p/screenie/)? And as a matter of fact I tried Screenie (compiled myself form Git) on an Kubuntu 10.10 with a stock Qt 4.7.0 (.0, not .1!) and default KDE theme, and Screenie does NOT crash! It also seems to work perfectly(*) on Mac OS 10.6.5 (also with Qt 4.7.0). In other words, only on Windows XP did I observe the above-mentioned crash in BLEND_SOURCE_OVER_ARGB32_SSE2, and that one apparently got fixed (on Windows) with Qt 4.7.1.

And: I changed the underlying Screenie QWidget to a QGLWidget, so the content was drawn with OpenGL (at least the transformations, the image itself is still painted/mirrored with a QPainter onto a QPixmap). This also worked without problems on Windows XP (Qt 4.7.1), Mac OS X 10.6.5 (Qt 4.7.0) and Kubuntu 10.10 (distro Qt 4.7.0) (on the later only with a software GL, since I ran it on a veeeery old HP Omnibook 6000, Pentium III ;)

So when you say you could only reproduce it with the "Oxygen" theme (isn't that the default theme on Kubuntu?) there must be something else buggy then?


(*) There IS however a graphical artifact on Linux and Mac, Qt 4.7.0: at the very bottom of the mirrored image there is a thin light-grey line, but only when I had images. Looks like a typical "off by 1" graphical artifact, not sure whether this is a bug in Screenie itself. I don't observe this on Windows XP with Qt 4.7.1 however.


Cheers, Oliver
--
Oliver Knoll
Dipl. Informatik-Ing. ETH
COMIT AG - ++41 79 520 95 22