Python/Tkinter/tk crash [long]

Hi all,

I was creating a Tkinter widget in the style of the reversed tabs below Excel
worksheets and I stepped in a serious problem: the code I made makes python
crash with a seg fault, bus error or X11 BadGC error on both Solaris (2.6 and
2.7) and Linux (Mandrake 8.0); it doesn't crash on Windows. I tried to simplify
the script, but I couldn't reproduce the crash with a simpler code. So the code
below is somewhat long; sorry for that.

To make it crash, just run the script and click on a tab. It usually crashes at
the first click, but you may have to play a bit with the tabs. I tried to run
Python through gdb to see where the crash happens, but it seems to be quite
random. Maybe a memory corruption?

There's a simple workaround, but with drawbacks: at the beginning of the
__update method, if I do not destroy and re-create the Canvas, but simply empty
its contents, the script works. But it keeps the commands declared created at
the tcl level for the former bindings, so it silently eats up memory.

My setup is Python 2.1 with tcl/tk 8.3.4. I searched the bug database but this
bug doesn't seem to be known. But maybe it was corrected in a newer Python or tk
version? Can anyone confirm that?

Thanks a lot in advance.

Here is the code:

--TabRow.py----------------------------------
from Tkinter import *


## CLASS GENERIC.CALLBAC K:
## =============== ========
# Instances are generic callbacks for buttons, bindings, etc...

class GenericCallback :

def __init__(self, callback, *commonArgs):
self.callback = callback
self.__commonAr gs = commonArgs

def __call__(self, *args):
return apply(self.call back, self.__commonAr gs + args)



## CLASS TAB.ROW:
## ==============
# Excel-style reverse tabs in a row

class TabRow(Frame):

## CLASS ATTRIBUTES:
## -----------------

defaultHeight = 24 # Default height for row
verticalMargin = 2 # Margin at the top and the bottom of the tabs
tabBorderWidth = 10 # Width for the descending and ascending lines at the
# border of tabs


## METHOD __INIT__:
## ----------------
# Constructor
# Parameters: the ones for the Frame class
# Recognized options: the ones for the Frame class +
# - tabs: list of tabs
# - currenttab: active element in tabs, or its index
# - tabchangecallba ck: function called when the user clicks on a tab
# (1 param = text; returns a boolean)
# - font: the font to use to display the texts in the tabs
# - activebackgroun d: the background for the current tab

def __init__(self, *args, **options):

## INSTANCE ATTRIBUTES:
## --------------------

self.__tabs = ()
self.__tabChang eCallback = None
self.__tabsCanv as = None
self.__currentT abIndex = 0
self.__tabPosit ions = None
self.__canvasHe ight = TabRow.defaultH eight

## Super-init
apply(Frame.__i nit__, (self,) + args)
## Configure/update
self.configure( options)


## METHOD CONFIGURE:
## -----------------
# Changes the options for the tab row

def configure(self, dictOptions={}, **options):
options.update( dictOptions)
## Get specific options
self.__tabs = options.get("ta bs", self.__tabs)
self.__tabChang eCallback = options.get('ta bchangecallback ',
self.__tabChang eCallback)
## Get index for current tab
if options.has_key ('currenttab'):
if type(options['currenttab']) == type(0):
self.__currentT abIndex = options['currenttab']
else:
indices = [i for i in range(len(self. __tabs))
if self.__tabs[i] == options['currenttab']]
if indices: self.__currentT abIndex = indices[0]
## Remember forced height for canvas if any
self.__canvasHe ight = options.get('he ight', self.__canvasHe ight)
## Remove unwanted options
needUpdate = 0
for o in ('tabs', 'currenttab', 'tabchangecallb ack',
'font', 'activebackgrou nd', 'height'):
if not options.has_key (o): continue
del options[o]
needUpdate = 1
if options.has_key ('bg') or options.has_key ('background'): needUpdate = 1
## If needed, apply options on the frame
if options:
apply(Frame.con figure, (self,), options)
## If needed, update display
if needUpdate: self.__update()


## METHOD __UPDATE:
## ----------------
# Updates the display

def __update(self):
## (Re)create canvas for tabs
if self.__tabsCanv as is not None:
self.__tabsCanv as.grid_forget( )
self.__tabsCanv as.destroy()
self.__tabsCanv as = Canvas(self, bg=self.cget('b ackground'),
height=self.__c anvasHeight)
self.__tabsCanv as.grid(row=0, column=0, sticky='nswe')
## Build tabs
tabIndex, pos = 0, 0
self.__tabPosit ions = []
activeTabRight = 0
for text in self.__tabs:
## Standard tag + specific tag if tab is the current one
tabTag = 'TAB_%s' % tabIndex
tags = [tabTag]
if tabIndex == self.__currentT abIndex: tags.append("CU RRENT_TAB")
tags = tuple(tags)
## Remember tab position
self.__tabPosit ions.append(pos )
## Draw text
textId = self.__tabsCanv as.create_text( pos + TabRow.tabBorde rWidth,
self.__canvasHe ight / 2,
text=text, anchor=W, tags=tags,
font=('helvetic a', 10, 'bold'))
## Polygon for tab, including line from left side if current tab
textBBox = self.__tabsCanv as.bbox(textId)
x = textBBox[2]
coords = [
pos, TabRow.vertical Margin,
pos + TabRow.tabBorde rWidth,
self.__canvasHe ight - TabRow.vertical Margin,
x, self.__canvasHe ight - TabRow.vertical Margin,
x + TabRow.tabBorde rWidth, TabRow.vertical Margin ]
if tabIndex == self.__currentT abIndex:
coords = [0, TabRow.vertical Margin] + coords
activeTabRight = x + TabRow.tabBorde rWidth
## Get polygon background
polygOpt = {'fill' : self.__tabsCanv as.cget('backgr ound'),
'outline':'', 'tags':tags}
if tabIndex == self.__currentT abIndex: polygOpt['fill'] = 'white'
## Draw polygon
polygId = apply(self.__ta bsCanvas.create _polygon, coords, polygOpt)
lineId = apply(self.__ta bsCanvas.create _line, coords,
{'fill':'black' , 'tags':tags})
## Put it under text
self.__tabsCanv as.lower(lineId )
self.__tabsCanv as.lower(polygI d)
## Binding for tab change
self.__tabsCanv as.tag_bind(tab Tag, '<ButtonReleas e-1>',
GenericCallback (self.__changeT ab, tabIndex, text))
## Update position and tab index
pos = x + TabRow.tabBorde rWidth / 2
tabIndex += 1
## End of display: draw line from active tab to right border
## and put active tab on top
self.__tabsCanv as.create_line( activeTabRight, TabRow.vertical Margin,
pos + TabRow.tabBorde rWidth / 2,
TabRow.vertical Margin)
self.__tabsCanv as.tag_raise("C URRENT_TAB")


## METHOD __CHANGE.TAB:
## --------------------
# Called when the user clicks on a tab

def __changeTab(sel f, tabIndex, text, event=None):
if self.__tabChang eCallback is None: return
if not self.__tabChang eCallback(text) : return
self.__currentT abIndex = tabIndex
self.__update()



if __name__ == '__main__':
root = Tk()

def ct(t):
print t
return 1

r = TabRow(root, tabs=('foo', 'bar', 'spam'), tabchangecallba ck=ct)
r.pack()
root.mainloop()
---------------------------------------------
--
- Eric Brunel <eric.brunel@pr agmadev.com> -
PragmaDev : Real Time Software Development Tools - http://www.pragmadev.com