Users with GNOME Shell installed have reported having issues with multi-monitor support when the monitors are not equally sized or the same aspect ratio.
If the application is moved from a smaller to larger monitor then the framebuffer will retain the size of the smaller monitor. Also if the monitors are reverse with the smaller on the left the Splash screen would start on the smaller but then the game would start and go fullscreen on a the larger (non-primary) monitor still with the smaller resolution framebuffer. Clicking on the black area outside (before the window has grabbed the mouse) will lock and warp the mouse to the outside area preventing it from entering the main area and preventing mouse input into the game.
The suggestion on Answerhub is because SDL maps all monitors as a large desktop (based on the screen information from xrandr). It looks as though the game is not correctly resizing or updating the framebuffer or window size when the window changes monitors.
This bug requires GNOME Shell installed on ubuntu and setup with two monitors one with a lower resolution than the other (for example one as 16:9 and one 16:10). Place the lower resolution monitor on the right and set it as the primary monitor.
To Install GNOME Shell on Ubuntu:
To reproduce the issue:
Head over to the existing Questions & Answers thread and let us know what's up.