Comment 22 for bug 736500

After reviewing code some more, I believe the issue lies in the X server. With the addition of masked valuators, you could have an event that has an X and Pressure value changes, but not a Y value change. The following is the axis mapping:

0: X
1: Y
2: Pressure

In XI 1.x, the protocol sends a range of changed values. If axis 0 and 2 change, 1 has to be sent with it. Since Y didn't change, axis 1 is being sent with a value of 0. It needs to send the previous value in this case.

The good news is that the fix shouldn't be too difficult. I will probably get to it early next week.