"""Check common desktop prerequisites before Qt can abort the process."""
import ctypes
import os
import sys


def desktop_error():
    if not sys.platform.startswith('linux'):
        return None
    backend = os.environ.get('QT_QPA_PLATFORM', '').split(':')[0]
    uses_xcb = backend == 'xcb' or (not backend and os.environ.get('DISPLAY') and not os.environ.get('WAYLAND_DISPLAY'))
    if uses_xcb:
        try:
            ctypes.CDLL('libxcb-cursor.so.0')
        except OSError:
            return ('Samsara needs the Qt X11 cursor library. On Debian-based desktops run:\n'
                    '  sudo apt install libxcb-cursor0\n'
                    'Then retry: python -m samsara.main\n'
                    'For other Linux distributions install the package providing libxcb-cursor.so.0.')
    return None