from gi.repository import Gtk

from gi.repository import cairo

import sys

import math

class MyWindow(Gtk.ApplicationWindow):

    def __init__(self, app):

        Gtk.Window.__init__(self, title="Choose an angle", application=app)

        self.set_default_size(400, 400)

        self.set_border_width(10)

        # a default angle

        self.angle = 360

        grid = Gtk.Grid()

        # a spinbutton that takes the value of an angle

        ad = Gtk.Adjustment(360, 0, 360, 1, 0, 0)

        self.spin = Gtk.SpinButton(adjustment=ad, climb_rate=1, digits=0)

        self.spin.connect("value-changed", self.get_angle)

        # a drawing area for drawing whatever we want

        self.darea = Gtk.DrawingArea()

        # that we describe in the method draw(), connected to the signal "draw"

        self.darea.connect("draw", self.draw)

        # we have to request a minimum size of the drawing area, or it will

        # disappear

        self.darea.set_size_request(300, 300)

        grid.attach(self.spin, 0, 0, 1, 1)

        grid.attach(self.darea, 0, 1, 1, 1)

        self.add(grid)

    # whenever we get a new angle in the spinbutton

    def get_angle(self, event):

        self.angle = self.spin.get_value_as_int()

        # redraw what is in the drawing area

        self.darea.queue_draw()

    def draw(self, darea, cr):

        # a 10-pixels-wide line

        cr.set_line_width(10)

        # red

        cr.set_source_rgba(0.5, 0.0, 0.0, 1.0)

        # get the width and height of the drawing area

        w = self.darea.get_allocated_width()

        h = self.darea.get_allocated_height()

        # move to the center of the drawing area

        # (translate from the top left corner to w/2, h/2)

        cr.translate(w / 2, h / 2)

        # draw a line to (55, 0)

        cr.line_to(55, 0)

        # and get back to (0, 0)

        cr.line_to(0, 0)

        # draw an arc centered in the origin, 50 pixels wide, from the angle 0

        # (in radians) to the angle given by the spinbutton (in degrees)

        cr.arc(0, 0, 50, 0, self.angle * (math.pi / 180))

        # draw a line back to the origin

        cr.line_to(0, 0)

        # drawing the path, and keeping the path for future use

        cr.stroke_preserve()

        # set a colour

        cr.set_source_rgba(0.0, 0.5, 0.5, 1.0)

        # and use it to fill the path (that we had kept)

        cr.fill()

class MyApplication(Gtk.Application):

    def __init__(self):

        Gtk.Application.__init__(self)

    def do_activate(self):

        win = MyWindow(self)

        win.show_all()

    def do_startup(self):

        Gtk.Application.do_startup(self)

app = MyApplication()

exit_status = app.run(sys.argv)

sys.exit(exit_status)