From QB64 Wiki
The _DESKTOPWIDTH function returns the width of the users current desktop.
- x& = _DESKTOPWIDTH
- No parameters are needed for this function.
- This returns the width of the user's desktop, not the size of any screen or window which might be open on that desktop.
- Only available for use in GL. SDL version does not support this keyword.
s& = _NEWIMAGE(800, 600, 256) SCREEN s& PRINT _DESKTOPWIDTH, _DESKTOPHEIGHT PRINT _WIDTH, _HEIGHT
- Explanation: This will print the size of the user desktop (in my case currently 1920, 1080), and then the size of the current screen (800,600).