tkinter window geometry

Eric Brunel eric.brunel at pragmadev.N0SP4M.com
Fri Nov 21 12:09:27 CET 2003


Zora Honey wrote:
> I'm trying to get a Tkinter window to open up in the same place on my 
> screen that I left it the last time I quit the application.  To do this, 
> I simply write the position to a file at "exit" and at startup, I read 
> the file.  Simple enough, but it doesn't work.  Oftentimes it's "close", 
> but over several iterations, the window will wander all over the screen. 
> In the output below, you can see that the x offset is "off" by +4 each 
> iteration.  Until I move the window.  Then x and y are off for one 
> iteration.  Then back to just x.
> 
> Anybody know what the heck is going on here?

Window geometry is handled by the window manager you're using, so knowing your 
platform and your window manager would help.

Anyway:

[snip script output]
> -------Code--------
> from Tkinter import *
> 
> if __name__=="__main__":
>      def die():
>         root.update_idletasks()
>         newGeometry='+%d+%d' % (root.winfo_x(), root.winfo_y())

That's one problem: you cannot be assured that winfo_rootx() and winfo_rooty() 
will actually return the same coordinates as geometry() does. AFAICT, the only 
valid input for geometry() is a former output from geometry(). So I'd do 
something like:

newGeometry = root.geometry()
i = newGeometry.find('+')
if i != -1:
   newGeometry = newGeometry[i:]
   print "out=", newGeometry
   if newGeometry != geometryConfig:
     ...
root.quit()   # Better than a sys.exit(0)


>         print "out=", newGeometry
>         if (newGeometry!=geometryConfig):
>             config=open("alarm.config", 'w')
>             config.write(newGeometry+'\n')
>         sys.exit(0)
> 
>      root=Tk()
>      try:
>          config=open("alarm.config")
>          geometryConfig=config.readline()[:-1]
>          config.close()
>          print "in=", geometryConfig
>          print "before=,", root.geometry(newGeometry=None)

Here, you set the geometry before the root window is actually built. It may be a 
problem. So I'd pack the button in the window and do an update_idletasks before 
reading and setting the geometry. I don't know if it will change anything to the 
behavior you get, but it may make your script more portable.

>          root.geometry(newGeometry=geometryConfig)
>          root.update()
>          print "after=", root.geometry(newGeometry=None)
>      except :
>          pass

Another (unrelated) problem: if the file alarm.config does not exist, 
geometryConfig is never set and the die function will crash... And I won't 
repeat here how much a bad habit it is to use "except:" without an exception 
type... ;-)

>      exitb=Button(root, text="Exit", command=die)
>      exitb.pack(side=LEFT)
> 
>      root.mainloop()
> 

Your script with all the modifications I've described works as expected on Linux 
Mandrake 8 with Python 2.1 and tcl/tk 8.3.4, with the KDE window manager.

HTH
-- 
- Eric Brunel <eric dot brunel at pragmadev dot com> -
PragmaDev : Real Time Software Development Tools - http://www.pragmadev.com





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