When moving from using the integrated screen to using an external screen. Qt 5.7 applications switch to using 2x scaling. This seems to be wrong, since the DPI of the integrated screen is 120 and on the external one only 108. Neither are at the a 144 where would should start scaling. Also the text is scaled as well when the drop in virtual DPI should cause it to remain the same size.

Disconnecting the external screen restores the original scaling on the integrated screen. And restarting the application while the external screen is connected also makes it come up correctly unscaled.