[Edu-sig] drawing with the mouse with turtle...solved?

[Brian Blais]

On Nov 12, 2010, at 8:48 PM, Brian Blais wrote:

> 
> On Nov 12, 2010, at 8:05 PM, Steven D'Aprano wrote:
> 
>> On Fri, 12 Nov 2010 19:24:50 -0500, Brian Blais wrote:
>> 
>>> I'd like to draw on a turtle canvas, but use the mouse to direct the
>>> turtle.  I don't see a good way of getting the mouse coordinates and the
>>> button state.
>> 
>> I think the right way to do that is by creating an event handler to the 
>> turtle. These docs are for Python 2.7 turtle, but they may be applicable 
>> to older versions as well:
>> 
>> http://docs.python.org/library/turtle.html#turtle.ondrag
>> 
>> I quote:
>> 
>>>>> turtle.ondrag(turtle.goto)
>> 
>>   Subsequently, clicking and dragging the Turtle will move it 
>>   across the screen thereby producing handdrawings (if pen is down).
>> 
>> 
>> That's probably all you need to do.
> 
> 
> that's what I tried first, with no luck.  I am on 2.6 on Mac OSX (Enthought distribution).  The following code:
> 
> 
> import turtle
> 
> turtle.reset()
> turtle.speed(0)
> turtle.ondrag(turtle.goto)
> turtle.pendown()
> 
> running it in ipython brings up a window, but clicking, dragging, or anything like that doesn't move the turtle or draw anything.  running it in just plain python brings up the window, but it instantly closes.  I added:  turtle.mainloop()
> 
> which keeps the window open, but the clicking or dragging still doesn't move the turtle or update the window in any way.
> 

Here is code that "works", with at least one small oddity:

import turtle

def gothere(event):
    turtle.penup()
    turtle.goto(event.x-360,340-event.y)
    turtle.pendown()

def movearound(event):
    turtle.goto(event.x-360,340-event.y)

def release(event):
    turtle.penup()

def reset(event):
    turtle.clear()

turtle.reset()
turtle.speed(0)

c=turtle.getcanvas()

c.bind("<Button-1>", gothere)
c.bind("<B1-Motion>", movearound)
c.bind("<ButtonRelease-1>", release)
c.bind("<Escape>",reset)

s=turtle.Screen()
s.listen()



the oddity is that the coordinate transformations, x-360 and 340-y, are done by eye and do not seem to be related to any of the coordinate values I could find.  my screen size is 300x400, the x and y canvas scales are 1 and 1, but if I try to transform with those numbers the mouse is clearly off.

any ideas?

			bb

-- 
Brian Blais
bblais at bryant.edu
http://web.bryant.edu/~bblais
http://bblais.blogspot.com/