Running a Qt 5.6 application with QT_DEVICE_PIXEL_RATIO=2 and QT_AUTO_SCREEN_SCALE_FACTOR=1 (or if the application enables AA_EnableHighDpiScaling) everything will be scaled twice.

This can be observed with QtCreator 3.6 (seems to enable high dpi scaling by itself) but also other 5.6 applications like qdbusviewer (here you need to specify both env variables).

In the screenshot on the left is QtCreator 3.5 from Qt 5.5.1 and on the right QtCreator 3.6 from the Qt 5.6 Beta. Both run under the same user with the same environment.