[Interest] Utilizing the GPU, how to start?

Uwe Rathmann Uwe.Rathmann at tigertal.de
Fri Jul 8 13:02:05 CEST 2016

On Fri, 08 Jul 2016 10:19:14 +0100, Giuseppe D'Angelo wrote:

> I think the question was more about measuring CPU and GPU performance
> than memory.

Yes, but as we don't have any problems with the performance of the render 
engine we never benchmarked it. And our problem - the time spent for 
creating the quick item subtree - does not depend on the GPU.

What I did is to check a couple of animations, we need for another 
product comparing Widgets, Quick and OpenGLWidget. All options have been 
fast enough for a pleasing result, but the widget version - no surprise - 
needs for the majority of them more CPU load.

( Unfortunately I had to rule out the QOpenGL path because of certain 
bugs )

> This point about memory usage however is extremely valid, and amongst
> other things shows that allowing styling in QML itself is hard if not
> impossible due to the QObject bloat (and privileging composition over
> vertical integration for "simple" UI elements makes you pay a lot for
> it.)

This is exactly my point - beside, that I believe ( hard to produce 
numbers ), that the consequences of this "bloat" are also significant for 
the overall performance.

That's why I'm trying to do my controls with scene graph node composition 
- as much as possible. But this is no fun either as the feature set 
offered by the QSG-nodes ( public or private ) is surprisingly limited 
and I had to implement very basic stuff, like creating vertex lists for 
gradients ( only vertical linear gradients are there ), raised/ sunken 
borders etc.


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