RDP sends scroll wheel events to wrong monitor

[thudson]

Using the RDP with a dual head display mouse scroll wheel events are being sent to the wrong monitor. When the mouse is on the second monitor, scroll wheel events are sent as if they were on the first monitor which causes a focus change and other bad behaviour.

xev running on the console shows the events correctly as coming from the second display (coordinates 2593,264):

ButtonRelease event, serial 39, synthetic NO, window 0x4400001,
    root 0x141, subw 0x0, time 684071, (2,107), root:(2593,264),
    state 0x1000, button 5, same_screen YES

But when using RDP the same events are received as if they are on the first head, instead of the second display:

ButtonPress event, serial 39, synthetic NO, window 0x4400001,
    root 0x141, subw 0x0, time 796041, (75,120), root:(97,283),
    state 0x0, button 5, same_screen YES

ButtonRelease event, serial 39, synthetic NO, window 0x4400001,
    root 0x141, subw 0x0, time 796041, (75,120), root:(97,283),
    state 0x1000, button 5, same_screen YES

The mouse was at 97,283 on the second display, which should have been sent as 2657,283sip.

This problem does not occur with VNC, but is present in 5.0.24 as well as the 5.1 beta and does not seem to depend on window manager or host extension version.

As an additional confusing point, if there is any mouse motion at the same time as the scroll wheel event then the events are sent at the correct coordinates on the second head.