JS window.devicePixelRatio returns 1 on retina displays with Qt 5.1.1 and Qt 5.2.0;
"@media only screen and (-webkit-min-device-pixel-ratio: 1.5),
only screen and (min-device-pixel-ratio: 1.5)" also fails to work.
Build fancybrowser app from Qt examples and open attached html on Mac with retina display. Compare to results in Chrome and Safari.