from __future__ import print_function
try:
    import Tkinter
except ImportError:
    import tkinter as Tkinter

#
# Create a GUI with a canvas whose items may be moved
# using the mouse.
#
class CanvasDemo:

    # __init__() and run() together serve the same
    # purpose as the main() function in other examples.
    def __init__(self):
        self.moving_item = None
        self.orig_color = None
        self.dragx = 0
        self.dragy = 0
        self.app = Tkinter.Frame()
        self.app.grid(sticky="nsew")
        self.make_ui(self.app)

        top = self.app.winfo_toplevel()
        top.columnconfigure(0, weight=1)
        top.rowconfigure(0, weight=1)

    def run(self):
        self.app.mainloop()

    # "make_ui" is similar to the one in tkinter_canvas.py
    # except we call "make_movable" for each item we create.
    def make_ui(self, app):
        c = Tkinter.Canvas(app, width=400, height=400, bg="cyan")
        app.columnconfigure(0, weight=1)
        app.rowconfigure(0, weight=1)
        c.grid(row=0, column=0, sticky="nsew")
        r = c.create_rectangle((10, 10, 20, 30), fill="green")
        self.make_movable(c, r)
        r2 = c.create_oval((100, 100, 300, 200), fill="blue")
        self.make_movable(c, r2)

    # "make_movable" simply registers callback functions for
    # when the user presses down on button 1 (usually the left
    # button), moves the mouse while button 1 is down, or
    # releases button 1.  All three callbacks are methods
    # of our class.  When the button is pressed, we record
    # which item the mouse was over, so subsequent drag and
    # release actions may be applied to the correct item.
    # To pass the extra argument on selection, we define
    # a local function with an "item" argument with a
    # default value of the item being registered.
    def make_movable(self, c, item):
        def on_select(event, self=self, c=c, item=item):
            self.on_select(event, c, item)
        c.tag_bind(item, "<Button-1>", on_select)
        c.tag_bind(item, "<B1-Motion>", self.on_drag)
        c.tag_bind(item, "<ButtonRelease-1>", self.on_release)

    def on_select(self, event, c, item):
        self.moving_item = (c, item)
        self.orig_color = c.itemcget(item, "fill")
        self.dragx = event.x
        self.dragy = event.y
        c.itemconfigure(item, fill="yellow")

    def on_drag(self, event):
        dx = event.x - self.dragx
        dy = event.y - self.dragy
        self.dragx = event.x
        self.dragy = event.y
        c, item = self.moving_item
        c.move(item, dx, dy)

    def on_release(self, event):
        c, item = self.moving_item
        c.itemconfigure(item, fill=self.orig_color)
        self.moving_item = None

if __name__ == "__main__":
    CanvasDemo().run()
    print("Finished")