Erratic mouse pointer behaviour with Spice / QXL in a multi-screen setup

Issue

• Mouse pointer starts jittering when dragging item in application
• For accessing a legacy application we use a virtual machine with 4 heads
• Xorg is configured to use these 4 heads without Xinerama. There's no window manager running, just plain Xorg.
• The application is started on a remote system using rexec and Xorg is just used for displaying the application
• The application expects Xorg to be using :0.x for displaying the 4 separate screens.
• While using a drag & drop operation in one of the applications on display :0.0, the mouse pointer starts jittering between to different horizontal positions. When moving the mouse further to the right, the mouse pointer is even displayed on display :0.1 even though the application can't reach :0.1. It seems that spice is generating the wrong coordinates for the mouse pointer.