OpenGL implementation disappointment in Qt 5.x



  • Hi!

    I found the commit "dd3a30090b3379e6f075bde826f9147e4237a043" which force usage of QQuickWidget instead of QQuickView in QtCreator Welcome Page. This forces whole QtCreator to use OpenGL even in text editor! Now QtCreator consumes more CPU and GPU power and works slower!

    I found that Qt 5.x has much more bugs and slowdowns compared to Qt 4.x. New OpenGL implementation is very slow and buggy (e.g. QOpenGLWidget vs QGLWidget).

    My question is: what are the advantages of new OpenGL implementation (QOpenGLWidget, QQuickWidget) if it is slower and slow down is not only in OpenGL widgets, but in whole window? I know that image resizing and rotating is faster on GPU, but other things not, so programmer should choose OpenGL only to image operation, not for whole window.

    For example: programmer wants to add QOpenGLWidget for signal visualisation (e.g. 300x200 px) and the whole windows is 1920x1080 px and it has a lot of widgets (lists, buttons, a lot of painting and updates by timers). With new Qt, the GPU and CPU must composite whole window, not only OpenGL widget, so this is first slowdown. Please imagine how will it work with OpenGL and V-Sync enabled? And please imagine how will it work with buggy OpenGL drivers? And the last thing: whole window still uses OpenGL even if the QOpenGLWidget is closed!


  • Lifetime Qt Champion

    Hi and welcome to devnet,

    To discuss such matters, I'd recommend posting on the interest You'll find there Qt's developers/maintainers (This forum is more user oriented)



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