Setting the colorgroup is useful to reuse the code to draw a mask if the slider supports transparceny. Do not reimplement this function, it's mainly there for compatibility reasons. This function is obsolete. It is provided to keep old programs working. We strongly advise against using it in new code.
Handles focus in events for the slider.
Reimplemented from QWidget. Handles focus out events for the slider. Reimplemented from QWidget. Handles key press events for the slider. Reimplemented from QWidget.