#!/usr/bin/python3

'''
Helper program to draw a background image on each screen of the system.
'''

import sys

from PyQt4.QtCore import Qt
from PyQt4 import QtGui


def die(msg):
    print(msg, file=sys.stderr)
    sys.exit(1)


def create_window(wallpaper, geometry):
    win = QtGui.QWidget()

    wallpaper = wallpaper.scaled(geometry.size(),
                                 Qt.KeepAspectRatioByExpanding,
                                 Qt.SmoothTransformation)
    palette = QtGui.QPalette()
    palette.setBrush(win.backgroundRole(), QtGui.QBrush(wallpaper))

    win.setPalette(palette)
    win.setAttribute(Qt.WA_X11NetWmWindowTypeDesktop)
    win.setGeometry(geometry)
    win.show()
    return win


def main():
    if len(sys.argv) != 2:
        die('usage: {} <path/to/wallpaper.png>'.format(sys.argv[0]))
    path = sys.argv[1]

    app = QtGui.QApplication(sys.argv)
    wallpaper = QtGui.QPixmap(path)
    if wallpaper.isNull():
        die('Failed to load {}'.format(path))

    desktop = app.desktop()
    # Keep a trace of the windows to ensure they are not garbage collected
    windows = []
    for idx in range(desktop.screenCount()):
        geometry = desktop.screenGeometry(idx)
        win = create_window(wallpaper, geometry)
        windows.append(win)

    return app.exec_()


if __name__ == '__main__':
    main()