Create a QOpenGLWidget and set it as a child for a QWidget. Then the QWidget and all other raster widgets in this window renders using OpenGL. It slows down the whole application, application speed depends on V-Sync and uses much GPU power for repainting raster widgets.
In the attachment there is simple example which describes the problem. It contains QLabel with FPS counter and two buttons which creates old QGLWidget and QOpenGLWidget. Timer updates the raster window at maximum speed. When QGLWidget is shown, the application still works correctly. When QOpenGLWidget is shown, raster window updates are limited to V-Sync (if enabled) and GPU is used (check "intel_gpu_top" or nVidia control panel).
- slows down all raster widgets in window,
- slows down whole computer (because GPU is used when it shouldn't be),
- when V-Sync is enabled and there are many raster updates, sometimes application works too slow for convenient usage.
- QOpenGLWidget shouldn't convert the whole window into OpenGL.
If it is not a BUG - please add a new feature which allows to use QOpenGLWidget as QGLWidget replacement.