Qt high-DPI display metrics native API usage

The Qt platform plugins provides QtGui with per-screen scale factors and DPI determined using native API. Which API are we using? Is there any other API we should use?

Native (OS/WS implements scaling)

These scale factors are returned through QWindow/QScreen::devicePixelRatio()

OS X
[NSView convertSizeToBacking]

iOS
UIView.contentScaleFactor

Wayland
wl_output.scale

Qt (QtGui implements scaling)

These scale factors are returned through QScreen::logicalDpi() and QScreen::pixelScale(). The DPI is often computed based on screen pixel size and physical size.

X11
screen pixel size
physical size: xcb_randr_get_output_info_reply_t mm_width mm_height

X11/KDE
Should we use a KDE API?

X11/GNOME
Should we use a GNOME API?

Windows
shcoredll.getDpiForMonitor()
Default DPI awareness setting: PROCESS_PER_MONITOR_DPI_AWARE.
Command line option: “dpiawareness”
DPI awareness is not set for AA_PluginApplication applications

Android
android.util.DisplayMetrics().density (for the primary display only)

eglfs
screen pixel size
physical size:

        Q_OS_LINUX: ioctl(framebufferDevice, FBIOGET_VSCREENINFO, fb_var_screeninfo)
	KMS: drmModeConnector::mmWidth mmHeight
        QT_QPA_EGLFS_PHYSICAL_WIDTH
        QT_QPA_EGLFS_PHYSICAL_HEIGHT