Screen management loses HiDPI functionality if QApplication is started in certain DPI awarenesses

Brief:

We are loading our QApplication instance during plug-in module instantiation (our product is a plug-in). If HiDPI functionality is concerned, we see problems, dependent on in which DPI awareness context the module has been loaded.

Details:

We identified the main source for these problems in that the screen management in Qt under Windows is relying on a hidden window created for the purpose of listening to display change notifications from the OS.

This works, as long as you can be sure that the process is configured correctly for your DPI requirements (typical standalone application use case). If not - e.g. you want to have per-monitor DPI aware top-level windows, but the process is configured as system aware or unaware, notifications about screen settings changes are not transmitted at all, since the screen manager is stuck in a wrong awareness, and thus limited in functionality.

Our current workaround is to scope the construction of the QApplication instance in a per-monitor-v2 awareness context, to allow the hidden screen management window to be constructed in a hidpi aware mode, and so allow all screen notifications, even if the process itself is not configured this way.

We believe that this is something crucial to be available for our plug-in use case, since we want to have the QApplication behave independently from the process and maximize hidpi functionality (e.g. any top-level windows/dialogs should be allowed to be created in per-monitor-v2 mode, even if the process does not allow it, and which currently does not work, since the QWindow does not scale correctly anymore due to limited screen management functionality).