Issue 834351: Mouse wheel crashes program (original) (raw)
Created on 2003-11-02 00:37 by garyrxx, last changed 2022-04-11 14:56 by admin. This issue is now closed.
Messages (12)
Author: Gary Richardson (garyrxx)
Date: 2003-11-02 00:37
The following program (by Michael Peuser) crashes as soon as the mouse wheel is moved. See my post to c.l.p. on Oct 29.
Gary Richardson
#------------------------- from Tkinter import * def _onMouseWheel(event): print event
root = Tk() root.bind('',_onMouseWheel) root.mainloop()
Author: Martin v. Löwis (loewis) * 
Date: 2003-11-02 18:37
Logged In: YES user_id=21627
What operating system are you using?
Author: Gary Richardson (garyrxx)
Date: 2003-11-03 02:42
Logged In: YES user_id=899035
I'm using Win98SE.
Author: Jon Ashley (ash101)
Date: 2003-12-04 17:02
Logged In: YES user_id=923903
Happens for me too, on Win2K with python 2.3.2. The fault is in TCL84.DLL at an offset of 1002a58c, if that means anything to anyone.
Author: John Fouhy (johnfouhy)
Date: 2004-10-26 04:13
Logged In: YES user_id=1084032
I can reproduce this bug. I am running Python 2.3.4 on WinXP SP2.
tk84.dll is version 8.4.3; tcl84.dll is also 8.4.3.
The mousewheel works correctly with a Tkinter.Text object with no additional bindings.
Author: John Speno (corvus)
Date: 2005-01-04 15:02
Logged In: YES user_id=2138
Me too. Python 2.3.4 with Tcl/Tk 8.4.9. Crash on Scroll Wheeling in WinXP SP 1. (users report it happening in SP 2 also).
I'll try to make this happen in pure Tcl/Tk rather than Tkinter too.
Author: John Speno (corvus)
Date: 2005-01-04 15:40
Logged In: YES user_id=2138
I wasn't able to reproduce this in pure Tcl/Tk (under Wish). No surprise there. In wish, I used this:
toplevel .top bind .top {puts 'foo'}
And mouse wheeling in the Toplevel widget made a bunch of 'foo's appear in the wish console without crashing.
HTH.
Author: Steve Davis (sdati)
Date: 2005-02-08 02:40
Logged In: YES user_id=1214285
I have determined the root cause of this problem. It actually does lie in Tk, but is only revealed by Python Tkinter because of the way Python deals with events.
From Tk source -- tkWinX.c:
case WM_MOUSEWHEEL: ... event.xany.send_event = -1 ...
This line causes Tk to call TkpGetString() when ExpandPercents() is called with '%A' (which is done by Python for ALL events, including ). This, in turn, causes segmentation fault because event.xkey.trans_chars and event.xkey.nbytes are not initialized.
So, the workaround from the Python side is pretty ugly, but I have tested it and verified that it works. There is probably a better way, but this was the obvious solution to me, since I have never needed to look at the Tkinter interface before:
In Tkinter.py, define a new _subst_format and _subst_format_str:
_subst_format_workaround = ('%#', '%b', '%f', '%h', '%k',
'%s', '%t', '%w', '%x', '%y',
'%D', '%E', '%K', '%N', '%W', '%T', '%X', '%Y', '%D')
_subst_format_str_workaround = " ".join(_subst_format_workaround)Note that '%A' entry in _subst_format is replaced with '%D' entry in _subst_format_workaround.
Now, in Misc._bind(),
if sequence == "": cmd = ('%sif {"[%s %s]" == "break"} break\n' % (add and '+' or '', funcid, self._subst_format_str_workaround)) else: cmd = ('%sif {"[%s %s]" == "break"} break\n' % (add and '+' or '', funcid, self._subst_format_str))
I am submitting this bug to Tcl/Tk maintainers to request that they fix (Project: Tk Toolkit Request ID 1118340), but in the meantime (and for all older versions of Tk), it seems like a workaround in the Tkinter code might be appropriate.
Author: nikolaus heger (orthorim)
Date: 2005-05-12 14:41
Logged In: YES user_id=933256
sdati, thanks for this workaround. it's awesome. i am now happily mouse-wheeling :)
I did make a small improvement to it so it works for all MouseWheel type events. Instead of if sequence == "": i say if type(sequence) == str and sequence.contains("MouseWheel"):
This way, all permutations of mouse events are covered, e.g. ""
Author: Georg Brandl (georg.brandl) *
Date: 2005-05-31 13:11
Logged In: YES user_id=1188172
Bumping, as it is still the same with 2.4 on my box.
Author: Terry J. Reedy (terry.reedy) *
Date: 2009-03-25 02:09
3.0.1, WinXP, with two 3.0 revisions:
from tkinter import * def _onMouseWheel(event): print(event)
root = Tk() root.bind('',_onMouseWheel)
In IDLE shell, nothing changes, wheel works normally.
In interpreter window, wheel continues to work normally. After click on tk window, wheel generates <tkinter.Event object at 0x00ACE970> messages in interpreter window.
Unless someone can verify that there is a problem in 2.6.1, or in 3.0.1 on other hardware, we should close this.
Author: Guilherme Polo (gpolo) *
Date: 2009-08-03 17:14
This is a tk issue, so the best way to fix this (if you don't want to install something newer than Python 2.4 on Windows) is to install a newer tcl/tk version.
Unfortunately the proposed workaround is way too specific, imagine if other bindings had similar problems with different binding substitutions.
If we want to be safe, Tkinter should be passing only valid substitutions for a given sequence but this is very awkward. But check what the bind manual says ".. Some of the substitutions are only valid for certain types of events; if they are used for other types of events the value substituted is undefined.", note how it doesn't say ".. if they are used for other types of events a segfault ensues".
History
Date
User
Action
Args
2022-04-11 14:56:00
admin
set
github: 39484
2009-08-03 17:14:02
gpolo
set
status: open -> closed
resolution: wont fix
messages: +
2009-04-26 22:21:40
ajaksu2
set
status: pending -> open
nosy: + gpolo
2009-03-25 23:20:14
loewis
set
status: open -> pending
2009-03-25 02:09:55
terry.reedy
set
nosy: + terry.reedy
messages: +
2009-02-13 04:46:17
ajaksu2
set
stage: test needed
type: behavior
versions: + Python 2.6, - Python 2.4
2003-11-02 00:37:18
garyrxx
create