In high DPI mode, the mouse event coordinates are scaled to the logical device pixel space, which means there is now "sub-(logical-)pixel" precision for mouse coordinates. Since the canvas should be rendered in the device pixel space (re D7973 and D7982)), it would also make sense for the mouse to be able to interact in the device pixel space. Currently with integral coordinates, the mouse can only interact in the logical pixel space.

This means all the code and classes (e.g. 1KoPointerEvent1) that uses mouse coordinates should be converted to use the floating point coordinates instead of the integral coordinates.