"""
Example showing for tkinter and ttk how to:
  -- Capture mouse clicks, releases and motion.
  -- Draw on a Canvas.

Authors: David Mutchler and his colleagues
         at Rose-Hulman Institute of Technology.
"""

import tkinter
from tkinter import ttk


class PenData(object):
    def __init__(self):
        self.color = 'blue'
        self.mouse_position_x = None
        self.mouse_position_y = None
        self.is_dragging = False


def main():
    pen_data = PenData()

    root = tkinter.Tk()

    main_frame = ttk.Frame(root, padding=5)
    main_frame.grid()

    instructions = 'Click the left mouse button to make circles,\n'
    instructions = instructions + 'drag the left mouse button to draw'
    label = ttk.Label(main_frame, text=instructions)
    label.grid()

    # Make a tkinter.Canvas on a Frame.
    # Note that Canvas is a tkinter (NOT a ttk) class.
    canvas = tkinter.Canvas(main_frame, background='lightgray')
    canvas.grid()

    # Make callbacks for mouse events.
    canvas.bind('<Button-1>', lambda event: left_mouse_click(event))
    canvas.bind('<B1-Motion>',
                lambda event: left_mouse_drag(event, pen_data))
    canvas.bind('<B1-ButtonRelease>',
                lambda event: left_mouse_release(pen_data))  # @UnusedVariable

    # Make a button to change the color.
    button = ttk.Button(main_frame, text='Flip pen color')
    button.grid()
    button['command'] = lambda: flip_pen_color(pen_data)

    button = ttk.Button(main_frame, text="Button on canvas")
    canvas.create_window(100, 50, window=button)
    root.mainloop()


def left_mouse_click(event):
    canvas = event.widget
    canvas.create_oval(event.x - 10, event.y - 10,
                       event.x + 10, event.y + 10,
                       fill='green', width=3)


def left_mouse_drag(event, data):
    # data.mouse_position_x and _y keep track of the PREVIOUS mouse
    # position while we are dragging.
    canvas = event.widget
    if data.is_dragging:
        canvas.create_line(data.mouse_position_x, data.mouse_position_y,
                           event.x, event.y,
                           fill=data.color, width=5)
    else:
        data.is_dragging = True  # Start dragging

    data.mouse_position_x = event.x
    data.mouse_position_y = event.y


def left_mouse_release(data):
    data.is_dragging = False


def flip_pen_color(data):
    if data.color == 'blue':
        data.color = 'red'
    else:
        data.color = 'blue'


# ----------------------------------------------------------------------
# Calls  main  to start the ball rolling.
# ----------------------------------------------------------------------
main()