QHighDpiScaling has two init/update functions:
- initHighDpiScaling(): called once during QGuiApplication construction
- updateHighDpiScaling(): called whenever (relevant) screen configuration changes
Currently the calls to updateHighDpiScaling() are made from
multiple places including platform code. Simplify by calling
it from two locations:
- QWindowSystemInterface::handleScreenAdded()
- QGuiApplicationPrivate::processScreenLogicalDotsPerInchChange()
Replace comment about early calls to qt_defaultDpi with a
test which calls qt_defaultDpiX/Y with no screens attached.
(Looking at the qt_defaultDpiX() implementation, it is unlikely
that there will be a problem as long as updateHighDpiScaling()
is called before QGuiApplication::primaryScreen() starts returning
a non-null value.)
Change-Id: I447db42894617495843a5cb531a1322b000fed62
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
776734576c