[Interest] smoothest way to zoom/pan QGraphicsView?

[Jean-Michaël Celerier]

In my experience setting a GL viewport makes everything much less snappy
(at least on linux & os x, did not test on windows).

Here is a video of my software with GL viewport: https://vid.me/kjRe
And without: https://vid.me/e2vu

As you can see (as far as one can see in such a video), when I move the
object with the GL viewport there is a visible lag between the position of
the cursor and the position of the object ; much less when there is only
software rendering.
The experience is even worse on macOS, but maybe because of the performance
cost of retina.
I also tried porting the main view to QtQuick 2 but it is roughly the same
"laggy" performance.


Best
-------
Jean-Michaël Celerier
http://www.jcelerier.name

On Fri, Apr 7, 2017 at 7:04 AM, Thiago Macieira <thiago.macieira at intel.com>
wrote:

> Em quinta-feira, 6 de abril de 2017, às 19:38:36 PDT, Patrick Stinson
> escreveu:
> > Without stripping down my code into a runnable example, is setTransform
> > considered to be too slow for 60Hz frame-rate updates from touch events?
> If
> > so, is there a better way to smoothly zoom and pan the graphics view?
>
> QGraphicsView is not architected correctly for smooth 60 fps.
>
> At least try to set a QOpenGLWidget as your viewport. It might help.
>
> --
> Thiago Macieira - thiago.macieira (AT) intel.com
>   Software Architect - Intel Open Source Technology Center
>
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