[REG] QML window become empty after devicePixelRatio changed

No source code, You can reproduction this issue by the official Example.

QT/Examples/Qt-5.9.3/quick/demos/calqlatr

I run this example on Qt-5.10.0 + Mac OSX 10.13.2, with two Display Device.

15.4 (2880 x 1800)    devicePixelRatio=2
23.5 (1080 x 1920)    devicePixelRatio=1

At the beginning, It runs fine on 15.4(2880x1800). After I drag the QML window to 23.5(1080x1920), It become empty.

I tested it on Qt-5.9.3, this issue didn't appear.