Created attachment 341608 [details]
log of gtk3-demo with debug

Test environment:
- windows 10 Pro x64 1607 build 14393.447
- gtk 3.22.4 32bits from msys

Display settings

- laptop 1366x768 screen 1 at bottom
- full hd screen 1920x1080 at top
- all 2 screen left aligned in extend mode
==> see the capture that show the settings and the bug (maximized window on screen 2 is the red rectangle)

Using gtk3-demo.exe
no matter if you maximize with double-click on the header bar or use the maximize button

case 1: maximize on screen 1 (bottom): OK
case 2: maximize on screen 2 (top: extended one): KO
- the window overflow on the right
   - outside any viewing part
   - close widget on header bar is out of view

- the window overflow on bottom of screen 2 
  - into screen 1, on 272 pixels
  - in all width

gtk3-demo.exe --gdk-debug=events

Here is a debug trace, I've just:
 - launched gtk3-demo with the above command
 - (the window opened on screen 1)
 - drag t to screen 2
 - clicked on maximize
 - (then clicked on my console windows still on screen 1, so you have extra debug lines until I hit ctrl+c)


 Max.