[Qt-interest] QGLWidget

[Nathan Carter]

Yes, this fixed it for me also.  I upgraded to Ubuntu 9.04 and that  
solved the problem.  Thank you!

Nathan


On May 27, 2009, at 2:01 AM, Fabien Brachere wrote:

> Le mardi 26 mai 2009 à 16:46 -0400, Nathan Carter a écrit :
>> I have an application I've written and am compiling in Qt 4.5.  It
>> uses a QGLWidget subclass I've written.  I create one instance of the
>> subclass and keep it offscreen, so that when previews of things need
>> to be generated, that object can be configured/populated with the
>> stuff to render, and then I call QGLWidget::renderPixmap() on it,
>> returning a pixmap.
>>
>> The problem is that on Mac and Windows this works great, but on Linux
>> the pixmaps returned are full of garbage data.  This is not a memory
>> issue (i.e., accessing freed memory) as far as I know, because my  
>> code
>> looks like this:
>>
>> 	// quickviewer is the instance
>> 	quickviewer->resize( w, h ); // desired width and height
>> 	QPixmap p = quickviewer->renderPixmap();
>> 	p.save( "test.png", "PNG" );
>> 	// inspect that file and it contains garbage;
>> 	// use p in the application and it shows up as garbage
>>
>> You see, no moment when any deallocation occurs, as far as I can
>> tell.  And yet, when I say "garbage" I mean streaks of random colors
>> and little bits of other images in memory, indicating I'm accessing
>> memory I shouldn't be accessing.  Thus, my confusion.
>>
>> Anyone else run across this same Linux-specific problem?  Did I do
>> something wrong?
>>
>
> I had the same problem with my Linux box and not Windows. It was a
> problem with the graphic's card driver (proprietary ATI driver). I
> updated my distribution to Mandriva 2009.1 and it was solved.
> I noticed that the problem doesn't occur with Qt 4.4.
>
> Fabien
>
>
>
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