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()