GetMotionEvents reports unchanged coordinates as 0
This seems intentional, but I haven't found it document anywhere: when a coordinate does not change, it is reported as 0 instead of its actual value in the replies to GetMotionEvent. The attached log is an example: I moved the cursor in the center of the screen like when drawing an 'L'; the coordinates jumped from about 600 or 400 to 0.
This makes it impossible to tell whether a coordinate is actually 0 or not.