This fixes operating the touch docker and other QML parts with touchscreen when using Qt 5.9.4 or later LTS (upstream bug https://bugreports.qt.io/browse/QTBUG-66718).
However, with Qt 5.9.3 or earlier, as well as Qt 5.10.0, there is a possibility of two click events being triggered when performing a touchscreen click. I have observed this behaviour with a test program. The rotation and zoom buttons on the touch docker shows this too.
This is related to D10988