On iOS and OSX we our devicePixelRatio() getters return 2.0 in the case of Retina displays. Also on Android, some devices have a of ration != 1, but Qt would always return 1, there.

Here is a list of some ratios: http://www.devicepixelratio.com/

Anyway, IMHO currently it is even good that we always get 1 as result, since there is currently no way to set the devicePixelRatio via API.