Got cherry-pick from master: Added feature: in calibration mode, when pressing the Enter key, the selected point snaps to the current mouse location (otherwise you sometimes have to hunt for the point when it is in a location of the projector image that is not mapped). Also: changed the window settings so that other windows can appear on top of it. This makes it possible to run other programs on the primary monitor while the mapping continues on the projector viewports/screens.