Provide functionality which allows the window position to be adjusted while the user is dragging it.

There's provision in Qt for constraining the window bounds when a window is resized (via the layout mechanism), but not when the window is moved without being resized. It could be nice to have a call which allows the window position to be adjusted while the user is dragging it. This could be useful for example to create floating palettes which snap to the edge of the screen when the user drags them.