Running Qt app on phone vs desktop

Publicnamer

How can I easily detect that I'm running on a smaller screen e.g. 5 to 7 inches, and therefore use the full screen area,
versus running on a desktop where the display may be huge and the app window smaller? For instance, if I try to infer it by looking at the resolution e.g. 1920x1080, that could apply to both a desktop and to a phone. Even if I get qApp->desktop()->logicalDpiX(); to get the screen dimensions, or I use getenv("QT_SCALE_FACTOR") to try to guess the rough screen size, some desktops have smaller screens e.g. the Raspberry pi 7 inch display.

mchinand

You can use QSysInfo

JoeCFD

QRect rect = QGuiApplication::screens().at( 0 )->geometry();
resize your app to the size of rect for full screen or compare the size to check if it is in the full screen mode

Publicnamer

@mchinand I'm not sure that will work with the PinePhone which runs various Linuxes.

Perhaps if the screen diagonal is less than 6.8 inches I could call it a phone.
However I'm finding that when I use QGuiApplication::screens().at(0)->geometry(), combined with dpiX and dpiY,
the diagonal screen measurement is not accurate, because the DPI values are obtained from the OS, not from the monitor.

Bonnie

6.8 inches means physical size, right? So I think you shouldn't use any logicalDpi*() methods for that.
Maybe try QScreen::physicalSize(), that should give you the physical screen size in millimeters.
Or you can search for other physicalDotsPerInch*() / physicalDpi*() methods if you want DPI infomations.

Publicnamer

@Bonnie The real problem here is that a screen of any size can be used like a desktop, or a phone screen.
For instance the Raspberry Pi 7" is always used like a desktop UI.
Thus it is a question of "user interface idiom" i.e. how the screen is meant to be used.