Problem resizing a window and button placement

[Thomas Passin]

On 2/26/2024 6:02 AM, Steve GS via Python-list wrote:
> Although your code produces the value of Ww outside the function, I do not see how I can use the value of Ww unless I close the program.

The configuration event hasn't fired at the time you include the print 
statement in the handler's def block, and therefore the print function 
inside your handler hasn't invoked.  It won't be invoked until you 
resize the window.

There is no point to saving the width and height outside your 
on_configure() function, because outside that function you can't know if 
they have been changed.  There could even have been a race condition 
where you use one but the other changes before you get around to using 
it.  It's better just to ask tk for the values whenever you need them, 
as you do inside your handler.

> import tkinter as tk
> 
> Ww = None  # What does this do? Why not Integer?
> WwZ = None
# These could be integers, like 0, but that would not be the correct
# window sizes at that point. The window is either not constructed or it
# has some definite size that is not zero.

> def on_configure(*args):
>          global Ww
>          global WwZ
>          Ww = root.winfo_width()
>          print("9  Ww Inside =<"+str(Ww)+">")  # works
>          WwZ = Ww * 2
>          print("11  WwZ Inside =<"+str(WwZ)+">")  # works
>          return(Ww)  #Can I use this?
>          
> root = tk.Tk()
> root.bind('<Configure>',on_configure)
> print("15  Ww Inside1 = <"+str(Ww)+">")
> #Ww2 = int(Ww) * 2  # fails
> print("17  WwZ Inside2 = <"+str(WwZ)+">")
> 
> root.mainloop()
> 
> Ww2 = int(Ww) * 2  #Works but only after the program stops
> print("21  Ww Outside2 = <"+str(WwZ)+">")
> # Can I have concentric loops?
> 
> 
> SGA
> 
> -----Original Message-----
> From: Alan Gauld <learn2program at gmail.com>
> Sent: Monday, February 26, 2024 4:04 AM
> To: Steve GS <Gronicus at SGA.Ninja>; python-list at python.org
> Subject: Re: RE: Problem resizing a window and button placement
> 
> On 26/02/2024 07:56, Steve GS via Python-list wrote:
> 
>> Then there is that discovery
>> element: Why is my original
>> idea not working? I still
>> cannot pass the value back
>> from the function.  What is
>> different about this function
>> that others would have given
>> me the value?
> 
> There is nothing different, see the code below.
> print() is a function like any other.
> In this case it is called after you close the window, ie after mainloop() exits.
> But any other function called inside
> mainloop - eg any other event handler can also access it.
> 
> For example, if you added a button:
> 
> def printW(): print("Button Ww = ", Ww)
> 
> bw = tk.Button(root, text="Print Width", command=printW)
> bw.pack()
> 
> You would be able to print the value on demand.
> 
>>> import tkinter as tk
>>>
>>> Ww = None
>>>
>>> def on_configure(*args):
>>>          global Ww
>>>          Ww = root.winfo_width()
>>>          print("Ww Inside =<"+str(Ww)+">")
>>>
>>> root = tk.Tk()
>>> root.bind('<Configure>',on_configure)
>>> root.mainloop()
>>>
>>> print("Ww Outside = <"+str(Ww)+">")
> 
> --
> Alan G
> Author of the Learn to Program web site
> http://www.alan-g.me.uk/
> http://www.amazon.com/author/alan_gauld
> Follow my photo-blog on Flickr at:
> http://www.flickr.com/photos/alangauldphotos
> 
>