Created attachment 352258 [details] [review]
Patch to restore previous behavior

When moving a window to the left side of the screen, the window is maximized on the left half of the screen. When moving a window to the right side of the screen, gnome-shell crashes:

Core was generated by `/usr/bin/gnome-shell'.
Program terminated with signal SIGSEGV, Segmentation fault.

+ Trace 237502

This is caused by meta_monitor_manager_get_logical_monitor_at returning NULL, causing update_move to dereference the NULL pointer stored in monitor. meta_monitor_manager_get_logical_monitor_at returns NULL in this case, because POINT_IN_RECT decides that x=2560 is not contained in a monitor with width=2560.

Digging into the history, this was apparently not a problem until commit 2df4ebff47, which changed the function call in update_move from meta_screen_get_current_logical_monitor_for_pos to meta_monitor_manager_get_logical_monitor_at. meta_screen_get_current_logical_monitor_for_pos, unlike meta_monitor_manager_get_logical_monitor_at, simply returned the first monitor if there was only one monitor present, skipping the POINT_IN_RECT check that now fails.

The attached patch restores the previous behavior and fixes the problem for me, but the algorithm probably needs a better fix, since I'd still expect it to fail when more than one monitor is present.