#!/usr/bin/env python

# An example of mouse interaction with cairo and Gtk+
#
# Copyright (C) 2013  Antonio Ospite <ospite@studenti.unina.it>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# References:
# https://developer.gnome.org/gtk3/3.6/gtk-getting-started.html#idm140520417717488

import gi

gi.require_version('Gtk', '3.0')
from gi.repository import Gdk, Gtk, GObject, Gio

import math
import colorsys


# from http://stackoverflow.com/questions/481144/
def in_circle(c_x, c_y, r, x, y):
    return math.hypot(c_x - x, c_y - y) <= r


def clamp(x, interval):
    if x < interval[0]:
        return interval[0]
    elif x > interval[1]:
        return interval[1]
    else:
        return x


class InteractiveCanvas(Gtk.DrawingArea):
    def __init__(self, width, height, *args, **kwargs):
        super(InteractiveCanvas, self).__init__(*args, **kwargs)

        self.width = width
        self.height = height

        self.x_offset = self.width / 2.0
        self.y_offset = self.height / 2.0
        self.radius = 20
        self.border = 4

        self.selectable = False
        self.selected = False
        self.drag_offset_x = 0
        self.drag_offset_y = 0

        self.x = self.width / 2.0
        self.y = self.height / 2.0

        self.set_size_request(width, height)
        self.connect('draw', self.on_draw)
        self.connect('configure-event', self.on_configure_event)

        self.add_events(Gdk.EventMask.BUTTON_PRESS_MASK |
                        Gdk.EventMask.BUTTON_RELEASE_MASK |
                        Gdk.EventMask.POINTER_MOTION_MASK)
        self.connect('button-press-event', self.on_button_press_event)
        self.connect('button-release-event', self.on_button_release_event)
        self.connect('motion-notify-event', self.on_motion_notify_event)

    def on_configure_event(self, widget, event):
        self.width = event.width
        self.height = event.height

    def on_draw(self, widget, cr):
        cr.rectangle(0, 0, self.width, self.height)
        cr.set_source_rgb(1.0, 0.5, 0.5)
        cr.fill()

        cr.arc(self.x, self.y, self.radius, 0, 2 * math.pi)

        _h = self.x / float(self.width)
        if self.selected:
            _l = 0.6
        else:
            if self.selectable:
                _l = 0.5
            else:
                _l = 0.2
        _s = self.y / float(self.height)
        _r, _g, _b = colorsys.hls_to_rgb(_h, _l, _s)
        cr.set_source_rgb(_r, _g, _b)
        cr.fill_preserve()

        cr.set_source_rgb(0, 0, 0)
        cr.set_line_width(self.border)
        cr.stroke()

    def on_button_press_event(self, widget, event):
        if self.selectable:
            self.selected = True
            self.drag_offset_x = self.x - event.x
            self.drag_offset_y = self.y - event.y
            self.queue_draw()

    def on_button_release_event(self, widget, event):
        self.selected = False
        self.queue_draw()

    def on_motion_notify_event(self, widget, event):
        if self.selected:
            self.x = clamp(event.x + self.drag_offset_x, [0, self.width])
            self.y = clamp(event.y + self.drag_offset_y, [0, self.height])
            self.queue_draw()
        else:
            old_selectable = self.selectable
            if in_circle(self.x, self.y, self.radius + self.border,
                         event.x, event.y):
                self.selectable = True
            else:
                self.selectable = False

            if self.selectable != old_selectable:
                self.queue_draw()


class InteractiveApp(Gtk.Application):
    def __init__(self, title, width, height, *args, **kwargs):
        super(InteractiveApp, self).__init__(*args, **kwargs)
        self.connect("activate", self.on_activate)
        self.title = title
        self.width = width
        self.height = height

    def on_activate(self, data=None):
        window = Gtk.Window(type=Gtk.WindowType.TOPLEVEL)
        window.set_title(self.title)

        canvas = InteractiveCanvas(self.width, self.height)
        window.add(canvas)
        window.show_all()
        self.add_window(window)


if __name__ == "__main__":
    app = InteractiveApp(
        "InteractiveApp", 640, 480,
        application_id="apps.test.interactiveapp",
        flags=Gio.ApplicationFlags.FLAGS_NONE)
    app.run(None)