I want to tweak the existing style at runtime, specifically QStyle::PM_ToolBarIconSize. Can this be done? As far as I can tell, you can only inherit QStyle and override pixelMetric().
Edit 1: In the specific case of QStyle::PM_ToolBarIconSize, I could use QToolBar::setIconSize, but that would set the icon size for just a single toolbar instance. I want to change the underlying style hint to affect all toolbars everywhere with one fell swoop. And QStyle::PM_ToolBarIconSize may not be the only style I want to tweak, it's just the first one I'm looking at that just so happens to have a "change this instance's icon size" function.
Edit 2: I can't just make a new style subclass because the current style is already a custom style based on style sheets. There are several styles that a user can choose from. I don't want to create a bunch of new styles just so I can tweak a couple of toolbar icon or menu height size settings.
This is the exact purpose of QProxyStyle.