[Python-bugs-list] [Bug #110824] Tkinter canvas blow-up: bbox(ALL) == None (PR#133)

[noreply@sourceforge.net]

Bug #110824, was updated on 2000-Aug-01 14:10
Here is a current snapshot of the bug.

Project: Python
Category: Tkinter
Status: Closed
Resolution: Wont Fix
Bug Group: 3rd Party
Priority: 5
Summary: Tkinter canvas blow-up:  bbox(ALL) == None (PR#133)

Details: Jitterbug-Id: 133
Submitted-By: aa8vb@yahoo.com
Date: Thu, 18 Nov 1999 13:34:44 -0500 (EST)
Version: 1.5.2
OS: IRIX 6.5


From: "Fredrik Lundh" <fredrik@pythonware.com>
Date: Tue, 2 Nov 1999 09:53:17 +0100
Subject: Re: Tkinter canvas blow-up:  bbox(ALL) == None

Randall Hopper <aa8vb@yahoo.com> wrote:
>      Apparently if the bounds of the items in a Tk canvas widget exceed
> MAXINT, bbox(ALL) returns None.  The attached Python script demonstrates
> this.
> 
>      Intuitively it seems like this is a bug since the contents of the
> canvas are maintained in floating point; integer bounds shouldn't be
> involved, should they?
> 
>      Is this a Tk bug or a Tkinter bug?

both.

Tkinter uses _getints instead of _getdoubles to
convert the bounding box to a tuple...

...but the reason you get None instead of an over-
flow error is that Tk returns an empty string in this
case (at least in 8.0.5).

-------------------------------------------------------------------------------
#!/usr/bin/env python                                                          

#                                                                              

#   canvas_test.py - Demonstrates a bug in Tkinter's Canvas widget             

#                    where bbox = None when the bbox exceeds signed MAXINT     

#                    (2^31 on most machines).                                  

                                                                               

from Tkinter import *                                                          

                                                                               

#                                                                              

# Create widgets                                                               

#                                                                              

root = Tk()                                                                    

canvas = Canvas( root, width = 300, height = 300 )                             

canvas.pack()                                                                  

canvas.create_rectangle( (-100,-100,100,100),                                  

                         outline = "#008000", fill="#800000", width = 3 )      

canvas.create_line( (-100,-100,100,100),                                       

                    fill="blue", width=3 )                                     

canvas.create_line( (-100,100,100,-100),                                       

                    fill="blue", width=3 )                                     

canvas.config( scrollregion = canvas.bbox( ALL ) )                             

                                                                               

#                                                                              

# Zoom the canvas until it's bounds get toasted because they exceed MAXINT     

#                                                                              

def TimerCB( canvas=canvas ):                                                  

  old = canvas.bbox( ALL )                                                     

  canvas.scale( ALL, 0.0, 0.0, 2.0, 2.0 )                                      

  new = canvas.bbox( ALL )                                                     

  print "Old = %s, New = %s" % ( old, new )                                    

  if new == None:                                                              

    raise SystemError, "canvas's bbox is toast (exceeds signed MAXINT)"        

  canvas.after( 300, TimerCB )                                                 

                                                                               

print "CANVAS ZOOM BLOW-UP TEST:\n"                                            

canvas.after( 1500, TimerCB )                                                  

root.mainloop()                                                                




====================================================================
Audit trail:
Thu Nov 18 14:06:40 1999	guido	changed notes
Thu Nov 18 14:06:41 1999	guido	moved from incoming to request

Follow-Ups:

Date: 2000-Aug-01 14:11
By: none

Comment:
bbox should use floats instead of ints, since Tcl/Tk can return them.

-------------------------------------------------------

Date: 2000-Aug-09 11:10
By: effbot

Comment:
this is a Tk feature.  the "canvas bbox" command uses integers internally, so there's not much we can do about it :-(
-------------------------------------------------------

For detailed info, follow this link:
http://sourceforge.net/bugs/?func=detailbug&bug_id=110824&group_id=5470