Bf Em
x
Ef
Window X coord for mouse.
Bf Em
y
Ef
Window Y coord for mouse.
Not applicable for
Bf Sy
GLUT_OFFSCREEN
Ef
windows.
Warping means moving, just as if the user had manually moved the mouse. This can generate mouse-motion callbacks. If your callback then moves the pointer again, you may end up in an endless loop. There is some discussion about changing this, but at present this is just a caveat for you, the user, to be aware of.