Move python turtle with mouse pointer

Question

I have been trying to save images capturing handwritten text for my handwritten text recognition project. For this purpose I am using the python turtle. I want to change the coordinates of the turtle (in pen up position) on the canvas by moving my mouse, and make it write (in pen down position) by moving the mouse while holding on the left mouse button. I am not able to implement this. Here is my code.

import tkinter
import turtle

sc = tkinter.Tk()
sc.geometry("1000x1000+100+100")

fr4 = tkinter.Frame(sc, height=500, width=600, bd=4, bg="light green", takefocus="", relief=tkinter.SUNKEN)

fr4.grid(row=2, column=2, sticky=(tkinter.N, tkinter.E, tkinter.W, tkinter.S))

# Canvas
canvas = tkinter.Canvas(fr4, width=1920, height=1080)
canvas.pack()

# Turtle
turtle1 = turtle.RawTurtle(canvas)
turtle1.color("black")
turtle1.shape("turtle")
turtle1.speed(100000)

def drag_handler(x, y):
    turtle1.ondrag(None)  # disable event inside event handler
    turtle1.goto(x, y)
    turtle1.ondrag(drag_handler)  # reenable event on event handler exit

turtle1.ondrag(drag_handler)

sc.mainloop()

Answer 1

Below's my implementation of what you describe. I've moved it out of Tk and squarely into turtle. However, I introduce low level Tk calls to implement the missing turtle onmove() event handler. Once that's in place, it becomes a matter of managing motion, clicks, releases and drags. Make sure to click first on the window's title bar to make it active:

from turtle import Turtle, Screen

MOVING, DRAGGING = range(2)  # states

def move_handler(x, y):
    if state != MOVING:  # ignore stray events
        return

    onmove(screen, None)  # avoid overlapping events
    yertle.penup()
    yertle.setheading(yertle.towards(x, y))
    yertle.goto(x, y)
    onmove(screen, move_handler)

def click_handler(x, y):
    global state

    yertle.onclick(None)  # disable until release
    onmove(screen, None)  # disable competing handler

    yertle.onrelease(release_handler)  # watch for release event
    yertle.ondrag(drag_handler)  # motion is now dragging until release

    state = DRAGGING

def release_handler(x, y):
    global state

    yertle.onrelease(None)  # disable until click
    yertle.ondrag(None)  # disable competing handler

    yertle.onclick(click_handler)  # watch for click event
    onmove(screen, move_handler)  # dragging is now motion until click

    state = MOVING

def drag_handler(x, y):
    if state != DRAGGING:  # ignore stray events
        return

    yertle.ondrag(None)  # disable event inside event handler
    yertle.pendown()
    yertle.setheading(yertle.towards(x, y))
    yertle.goto(x, y)
    yertle.ondrag(drag_handler)  # reenable event on event handler exit

def onmove(self, fun, add=None):
    """
    Bind fun to mouse-motion event on screen.

    Arguments:
    self -- the singular screen instance
    fun  -- a function with two arguments, the coordinates
        of the mouse cursor on the canvas.

    Example:

    >>> onmove(turtle.Screen(), lambda x, y: print(x, y))
    >>> # Subsequently moving the cursor on the screen will
    >>> # print the cursor position to the console
    >>> screen.onmove(None)
    """

    if fun is None:
        self.cv.unbind('<Motion>')
    else:
        def eventfun(event):
            fun(self.cv.canvasx(event.x) / self.xscale, -self.cv.canvasy(event.y) / self.yscale)
        self.cv.bind('<Motion>', eventfun, add)

screen = Screen()
screen.setup(500, 600)
screen.screensize(1920, 1080)

yertle = Turtle('turtle')
yertle.speed('fastest')

state = MOVING

# Initially we track the turtle's motion and left button clicks
onmove(screen, move_handler)  # a la screen.onmove(move_handler)
yertle.onclick(click_handler)  # a click will turn motion into drag

screen.mainloop()

The onmove() event implementation is from my answer to Find the cursor's current position in Python turtle, feel free to give it an upvote when you visit. (Just as your drag_handler() is from my answer to Turtle freehand drawing, feel free to give that one an upvote if you haven't already.)