[Interest] QGraphicsView and QOpenGLWidget

[maitai]

Hello,

I am experimenting with setting the viewport of a qgraphicsview to 
qopenglwidget. It seems to work on windows and android (which I didn't 
expect). I have some basic questions, I already know a bit of openGL but 
I'm far from being an expert...

Is there any advantage to do that if you do not reimplement any GL 
native painting for any item? In clear is it going to be any faster? For 
instance for the time being I prefer to resize pixmaps using QPainter 
and set them back to QGraphicsPixmapItem instead of resizing the 
QGraphicsPixmapItem itself, but maybe it is going to be faster the other 
way round now?

I also need to render the full view in an image (QPixmap or QImage) 
quite often, so I was hopping that I could use 
QOpenGLWidget::grabFrameBuffer() on the viewport instead of 
QGraphicsView::render(), again to make it faster, but the only thing I 
get from grabFrameBuffer is a plain black QImage...


Thanks for any tip or advise
Philippe Lelong