[Development] The place of QML

Uwe Rathmann Uwe.Rathmann at tigertal.de
Fri May 18 13:01:32 CEST 2012

On 05/18/2012 09:07 AM, marius.storm-olsen at nokia.com wrote:
> Often it's hard to beat the performance of the main CPU(s for most people
> these days) filling in a polygon directly, rather than handing it off to a
> GPU.

Guess this is the reason behind the decision why in Qt 4.8 raster has 
become the default graphics system on X11 - what more or less means 
turning hardware acceleration off
( maybe it's worth to mention that QPainter is not synonym for software 
renderer - QPainter/X11 and QPainter/OpenGL are usually hardware 
accelerated ).

While I can't confirm that the CPU does things faster for the most 
relevant use cases I have in the Qwt library ( + the result is terrible 
for remote X11 or NX ), I can imagine that there are other use cases 
where this is true. F.e. on my box it is way faster to fill a QImage 
with a gradient + converting it expensively to a QPixmap, than to fill 
the QPixmap with the X11 paint engine. Don't know why - but, maybe this 
is an example where a scene graph could do things better ?

But before you read me wrong: I'm absolutely not against having a new 
and better graphic system - all I wanted to say is to be careful with 
performance statistics.


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