Informatik10/tk_canvas/my_canvas.py

import tkinter as tk
import tkinter.ttk as ttk

class Controller(object):
    def __init__(self, app):
        self.app = app

        self.selected = None
        self.selected_start = None
        self.selected_end = None

    def run_process(self):
        print("Run")
        self.app.main_canvas.bind('<1>', self.make_circle)
        self.app.main_canvas.bind('<3>', self.select_item)
        self.app.main_canvas.bind('<Shift-1>', self.select_for_line)
        return 0

    def make_circle(self, event):
        x = event.x
        y = event.y
        r = 20
        self.app.main_canvas.create_oval(x-r, y-r, x+r, y+r, fill="white", outline="black", tag="circle")

    def select_item(self, event):
        self.app.main_canvas.bind('<Motion>', self.move_item)
        self.app.main_canvas.bind('<1>', self.deselect_item)
        self.app.main_canvas.addtag_withtag('selected', tk.CURRENT)

    def deselect_item(self, event):
        self.app.main_canvas.dtag('selected')
        self.app.main_canvas.unbind('<Motion>')
        self.app.main_canvas.bind('<1>', self.make_circle)

    def move_item(self, event):
        x = event.x
        y = event.y
        r = 20
        self.app.main_canvas.coords("selected",x-r, y-r, x+r, y+r)

    def select_for_line(self, event):
        self.app.main_canvas.addtag_withtag("sel_line", tk.CURRENT)
        start_coords = self.app.main_canvas.coords("sel_line")
        self.x0 = (start_coords[0] + start_coords[2]) // 2
        self.y0 = (start_coords[1] + start_coords[3]) // 2
        x = event.x
        y = event.y
        self.app.main_canvas.create_line(self.x0,self.y0,x,y, tag="newline")
        self.app.main_canvas.bind('<Motion>', self.move_line)

    def move_line(self, event):
        x = event.x
        y = event.y
        self.app.main_canvas.coords("newline",self.x0,self.y0,x,y)

class Application(tk.Tk):
    def __init__(self):
        super().__init__()
        self.con = Controller(self)
        self.create_control_variables()
        self.create_widgets()

    def create_control_variables(self):
        pass

    def create_widgets(self):
        self.main_canvas = tk.Canvas(master=self,  width=500, height=400, background='gray75')
        self.main_canvas.grid(row=0, column=0)

        self.b = ttk.Button(master=self, text="Start", command=self.con.run_process)
        self.b.grid(row=1, column=0)


# --------------------------
# Execution
# --------------------------
if __name__ == "__main__":
    app = Application()
    app.mainloop()