#!/usr/bin/env python
# coding=utf8
# This file is part of Xpra.
# The code was taken from here:
# http://zetcode.com/gfx/pycairo/transparency/
# And is apparently GPL v2
# Xpra is released under the terms of the GNU GPL v2, or, at your option, any
# later version. See the file COPYING for details.

from xpra.gtk_common.gobject_compat import import_gtk, import_gobject
gtk = import_gtk()
gobject = import_gobject()
import cairo
import math


class cv(object):

    trs = (
        ( 0.0, 0.15, 0.30, 0.5, 0.65, 0.80, 0.9, 1.0 ),
        ( 1.0, 0.0,  0.15, 0.30, 0.5, 0.65, 0.8, 0.9 ),
        ( 0.9, 1.0,  0.0,  0.15, 0.3, 0.5, 0.65, 0.8 ),
        ( 0.8, 0.9,  1.0,  0.0,  0.15, 0.3, 0.5, 0.65 ),
        ( 0.65, 0.8, 0.9,  1.0,  0.0,  0.15, 0.3, 0.5 ),
        ( 0.5, 0.65, 0.8, 0.9, 1.0,  0.0,  0.15, 0.3 ),
        ( 0.3, 0.5, 0.65, 0.8, 0.9, 1.0,  0.0,  0.15 ),
        ( 0.15, 0.3, 0.5, 0.65, 0.8, 0.9, 1.0,  0.0, )
    )

    SPEED = 100
    CLIMIT = 1000
    NLINES = 8


class Example(gtk.Window):

    def __init__(self):
        super(Example, self).__init__()
        self.init_ui()

    def init_ui(self):
        self.darea = gtk.DrawingArea()
        self.darea.connect("expose-event", self.expose)
        self.add(self.darea)

        self.count = 0
        gobject.timeout_add(cv.SPEED, self.on_timer)

        self.set_title("Waiting")
        self.resize(250, 150)
        self.set_position(gtk.WIN_POS_CENTER)
        self.connect("delete-event", gtk.main_quit)
        self.show_all()


    def on_timer(self):
        self.count = self.count + 1
        if self.count >= cv.CLIMIT:
            self.count = 0
        self.darea.queue_draw()
        return True

    def expose(self, widget, cr):
        cr = widget.window.cairo_create()
        cr.set_line_width(3)
        cr.set_line_cap(cairo.LINE_CAP_ROUND)
        w, h = self.get_size()
        cr.translate(w/2, h/2)
        for i in range(cv.NLINES):
            cr.set_source_rgba(0, 0, 0, cv.trs[self.count%8][i])
            cr.move_to(0.0, -10.0)
            cr.line_to(0.0, -40.0)
            cr.rotate(math.pi/4)
            cr.stroke()


def main():
    Example()
    gtk.main()


if __name__ == "__main__":
    main()
