5.3.1: canvas doesn't process mouse events on part of the screen (full screen + multi-monitor)

I just filed bug #755480 for a bug with full screen mode in a multi-monitor setup. Parts of the canvas stop responding to mouse events, based on the *other* monitor's resolution. It's related to the regression introduced in 5.3.0, which it appears wasn't completely fixed in 5.3.1.

I have a Win10 computer with two monitors. Left one is rotated (effective resolution 1080x1920) while right one is standard (1920x1080). Windows identifies right one as #1, left one as #2.

Problems:

1. When I...

5.3.1: canvas doesn't process mouse events on part of the screen (full screen + multi-monitor)