I have a dual monitor setup. When I open a QMenu (eg. context menu) and it touches the right corner of the right screen, submenus open on the right corner of the left screen rather than to the left of their parent.
If the sub menu is even just a single pixel away from the corner of the screen the menu is properly positioned left of its parent.
Submenus of the misplaced submenu are also misplaced, opening right of their parent (ie. at the left corner of the right screen, rather than - again - left of their parent); not sure if this is intentional, though, as the menu wouldn't be torn apart.
Screen 0: minimum 320 x 200, current 3600 x 1200, maximum 16384 x 16384
DisplayPort-0 connected primary 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
1920x1080 60.00 50.00
1280x720 60.00 50.00 59.94
800x600 60.32 56.25
720x480 60.00 59.94
640x480 60.00 59.94
HDMI-0 disconnected (normal left inverted right x axis y axis)
DVI-0 connected 1680x1050+1920+0 (normal left inverted right x axis y axis) 434mm x 270mm
1280x1024 75.02 60.02
1024x768 75.08 60.00
800x600 75.00 60.32
640x480 75.00 60.00