[Development] Qt High-dpi QtCS report and patch status (on hold)

[Sorvig Morten]

A quick report from the contributors summit (I apologize for the delay and sketchy notes):

* I went though the general approach:

- Setting the scale factor:
	- platform plugin: QWindow::devicePixelRatio, QScreen::devicePixelRatio
	- the user: QT_HIGHDPI_SCALE_FACTOR=2
	- per-screen config file?

- Layering 
	- QtWidgets / QtQuick / Application : device-independent pixels
	- QPA: QWindow/QWindowSystemInterface :    scaling layer
	- Platform plugins:  device pixels

- QWindow and platform plugins
	- setGemetry()/geometry() is in device-independent pixels
	- platform plugins must scale when using QWindow API

* There was discussion on several points:
	- There are font kerning issues on Linux (and probably Windows) due to the scaling. How can we resolve this?
	- Do we really want to add scaling to QtGui? The alternative is to wait until there is OS support.
	- Windows and its three high-dpi modes.

On to the patch status: (https://codereview.qt-project.org/#/c/86107/)

Based on the patch reviews on gerrit and some discussion on irc I’ve decided that we don’t have a good enough consensus to merge the patches. I’m putting them on hold until after the summer break at least.

Morten