Zsiros Levente wrote:
[snip code]
*def* handler(event):
*if* buttonpressed == 1 :
/#if the mousebutton is pressed and moved, circles should
appear, but they do not/
can.create_oval(event.x-r, event.y-r, event.x+r, event.y+r,
fill="orange")
lab.config(text='buttonpressed=' + str(buttonpressed) )
*def* press(event):
buttonpressed=1
lab2.config(text=buttonpressed)
*def* release(event):
buttonpressed=0
lab2.config(text=buttonpressed)
[snip code]
/#global buttonpressed/
buttonpressed=0
I think you're misunderstanding what global variables are.
Take the following example:
#--- code
a = 0
def b():
print a
b()
#--- output
0
#---
the function 'b' can see the variable 'a'. ok so far.
now take this example.
#--- code
a = 0
def b():
a = 1
print a
b()
print a
#--- output
1
0
#---
in this case, 'a' is assigned to, but it's a local variable called 'a'
and not the one I think you expect it to assign to.
so after 'b' is done the value of the 'a' outside of the scope of the
function is still 0.
in your press and release events you assign values to 'buttonpressed'
before you use them,
and because of this, the same thing happens as in our second example: a
local variable named
'buttonpressed' is created with the value 0 or 1 assigned to it
(depending on the function you're in.)
that works fine, and it sets the label's text value accordingly. But,
since it's a local variable and the
functions aren't actually modifying the global 'buttonpressed', the
'buttonpressed' that you're checking for
in your 'handler' function is always going to be 0. That's why your
oval code is never drawn.
Rather than messing with global variables, which are for the most part
evil creatures,
as we've witnessed so far here, I'd recommend using a class.
I wrote the class I would use for you so you can see it.
It's commented, but if you need any more help than the comments feel
free to write me back.
Just be sure to use the reply-all button so the whole list can see the
response.
-Luke
(note: code attached)
#!/usr/bin/python
# This program implements <B1-motion>. it was originally written by
#Zsiros Levente. all rights of this modified version go to him :)
from Tkinter import *
class ButtonHandler(object):
def __init__(self):
#our self.mousedown variable is what we'll use to check the state
#of the button, since we're going to be passing a copy of 'self'
#around, we don't have to deal with scoping of the variables.
#I.E. self.mousedown is global to functions in the class
#that accept a 'self' argument.
self.mousedown = 0
#we make the window normally. note all these are 'self' variables
#so we can change them easily elsewhere in the class.
self.root = Tk()
self.root.geometry('600x500+200+200')
self.label = Label(self.root, text=str(self.mousedown))
self.can = Canvas(self.root, width='500', height='400', bg='white')
#lambda is a way we can add extra arguments to a function.
#since the callback of bound events is only a single argument,
#we use 'lambda x' to get the 'event' instance, and pass it
#along with another string identifying which event it came from.
#this may or may not be necessary, but it's cool and it
#makes the handler function make more sense.
#also, we only need one handler function this way.
self.can.bind("<Motion>",lambda x:self.handler(x,'motion'))
self.can.bind("<Button-1>",lambda x:self.handler(x,'press'))
self.can.bind("<ButtonRelease-1>",lambda x:self.handler(x,'release'))
self.label.pack()
self.can.pack()
self.root.mainloop()
def handler(self,event,x):
#the first two clauses of the if-elif branch implement your
#'press' and 'release' functions.
if x == 'press':
self.mousedown = 1
elif x == 'release':
self.mousedown = 0
elif x == 'motion':
if self.mousedown:
#you could do something really cool here, like store the time
#that the button was last pressed, and increase the radius of
the circle
#depending on how long it's been since then.
r = 5
self.can.create_oval(event.x-r, event.y-r, event.x+r,
event.y+r, fill="orange")
self.label.config(text=str(self.mousedown))
#we create an instance of the class which automatically
#calls the '__init__' method.
x = ButtonHandler()
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