Comment 4 for bug 1564830

BTW, absolute pointer events keep coming even when not touching the screen. Because the stylus is detected even when it's nearby.

This means you can visually move the cursor without touching the screen. When you touch the screen ABS_PRESSURE increases. When the pen leaves the screen, ABS_PRESSURE drops to zero but ABS_X and ABS_Y still gets reported while it's hovering nearby.