This fixes a bug causing the wrong DPI being used when moving the window from a screen to another screen to the left. Using the top-left position of the window to determine screen changes doesn't work well since the device pixel ratio of a window does not change until the window is roughly halfway across.

1. Use two screens with different DPI scaling.
2. With the window on the left screen, open an image and note the image size at 100% zoom.
3. Move window from the left screen to the right screen then back to the left screen.
4. Verify that the image size is the same as before.