From: Jakub Travnik <jtra@...>
Date: 2002-09-16T22:50:45+09:00
Subject: Re: [BUG] in win32 tcltk/ruby FocusIn/FocusOut events

Jakub Travnik wrote:
> 
> Hello,
> 
> I have found a bug in win32 tcltk/ruby.
> Following code demonstrates the problem:
> ----cut_here-------------------
> require 'tk'
> 
> root=TkRoot.new
> e1=TkEntry.new root, 'width'=>10
> e2=TkEntry.new root, 'width'=>10
> e1.pack 'side'=>'left'
> e2.pack 'side'=>'left'
> 
> e1.bind 'FocusIn', proc { puts 'focus in'}
> e1.bind 'FocusOut', proc { puts 'focus out'}
> 
> Tk.mainloop
> -------------------------------
> 
> After events trigger (by focusing entry boxes), ruby crashes:
> ----cut_here-------------------
> focus in
> C:/PROG/RUBY/lib/ruby/1.6/tk.rb:620: [BUG] Segmentation fault
> ruby 1.6.7 (2002-03-01) [i586-mswin32]
> 
> abnormal program termination
> -------------------------------
> 
> If you change 'FocusIn' to 'Enter' and 'FocusOut' to 'Leave',
> no bug occurs and code works fine (however with different
> functionality, since original intent was to highlight TkEntry
> that has keyboard focus, this does not solve my problem).
> 
> Affected versions
> (both tested are from the Pragmatic Programmers distribution):
> 
> * Ruby Installer for Windows, Ruby Version 1.6.7, Installer Version 4,
>   tcl/tk readme header shows:
>   Tcl/Tk 8.3 for Windows, Binary Distribution
>   RCS: @(#) $Id: README.binary,v 1.19.2.1 2000/07/27 01:39:23 hobbs Exp $
> 
> * And older version 1.6.4-3 of ruby installer.
> 
> By win32 I mean the tested windows version which was:
> Windows 95 OSR2 Czech.
> 
> Unaffected:
> * linux version: ruby 1.6.7 (2002-03-19) [i386-linux] / tcltk 8.3
> 
> 
> BUG does not seem to be in tcl/tk itself since following tcl script works
> under win32 correctly:
> ----cut_here-------------------
> entry .e1 -width 10
> entry .e2 -width 10
> label .l1 -text "initial"
> pack .e1 -side left
> pack .e2 -side left
> pack .l1 -side left
> bind .e1 <FocusIn> {.l1 configure -text "focus in"}
> bind .e1 <FocusOut> {.l1 configure -text "focus out"}
> -------------------------------
> Note: output to label was due to unavailable stdout.
> 
> I have also tested some older version of Python 1.5.2
> under win32 with tcl/tk 8.0
> ----cut_here-------------------
> from Tkinter import *
> def myprint(x):
>   print x
> root=Tk()
> e1=Entry(root, width=10)
> e2=Entry(root, width=10)
> e1.pack(side='left')
> e2.pack(side='left')
> e1.bind('<FocusIn>', lambda e: myprint("focus in"))
> e1.bind('<FocusOut>', lambda e: myprint("focus out"))
> mainloop()
> -------------------------------
> No problem ocurrs.
> 
> Ruby ran with RUBY_TCL_DLL and RUBY_TCL_DLL pointing to tcl/tk
> distributed with the python (tcl/tk 8.0) does not make any difference,
> the bug still happen.
> 
> I don't have windows compiler to experiment more deeply.
> 
> BUG seems to be triggered from tcltklib to which is the
> last call before crash when stepping source with ruby -rdebug.
> 
> Best regards,
> 
> Jakub Travnik
> jabber://jtra@jabber.com
> 
> P.S.: searching ruby-talk archive show that this bug has been noticed
> before but with no attempt to correct it. But since python can do it
> and ruby tcl/tk is modeled after python's so it should be fixable.
> 

Hello,

I have solved the problem. Bug is in the Tk itself, see following
tcltk code:
----cut_here-------------------
entry .e1 -width 10
entry .e2 -width 10
label .l1 -text "initial"
pack .e1 -side left
pack .e2 -side left
pack .l1 -side left
bind .e1 <FocusIn> {.l1 configure -text %S}
bind .e1 <FocusOut> {.l1 configure -text %S}
-------------------------------

This will crash in Tk_GetHWND called from TkpPrintWindowId
called from case "%S" in ExpandPercents when FocusIn/FocusOut event
happen.

Since ruby does use %S in every bind where no explicit
percent string is supplied, bug happens. Python does not use this
so bug does not happen with it.

Quick fix for ruby is to bind with other percent string, in this
case, empty is sufficient.
----cut_here-------------------
require 'tk'

root=TkRoot.new
e1=TkEntry.new root, 'width'=>10
e2=TkEntry.new root, 'width'=>10
e1.pack 'side'=>'left'
e2.pack 'side'=>'left'

e1.bind 'FocusIn', proc { puts 'focus in'}, "" # <--- EMPTY STRING HERE
e1.bind 'FocusOut', proc { puts 'focus out'}, "" # <--- EMPTY STRING HERE

Tk.mainloop
-------------------------------

Long term fix is to remove %S from tk.rb file depending on event, or
fix tcl/tk windows version to behave in correct way for this situation.

Best regards,

Jakub Travnik,
jabber://jtra@jabber.com