[wxPython] wxListCtrl_virtual crashes and I can't find what I'm doing wrong

[F. GEIGER]

Thank you, Robin, for answering that quick!

"Robin Dunn" <robin at alldunn.com> schrieb im Newsbeitrag
news:407C1D34.8000205 at alldunn.com...
> F. GEIGER wrote:
> [...]
>
> > And now I have problems:
> >
> > This control is named VipAPSpooler. It first used a wxTimer, to update
> > itself periodically: If the underlying model had changed in the number
of
> > items, it exec'ed a DeleteAllItems() and a SetItemCount().
>
> Since it's virtual just a SetItemCount should be enough.

Okay, I'll try that.


>
> >
> > This did not work: The debugger halted in the MainFrame's(!)
on-idle-method
> > in line
> >
> > currentTitle = self.GetTitle()
> >
> > saying "Inappropriate argument type: an integer is required".
>
> If an exception happens in some of the C++ wrapper code (such as after
> returning from an event handler or a callback), then the next time
> control enters Python code the exception is detected and raised from
> that point.  Normally the C++ code will detect the situation and print
> the traceback and then clear the error, but it's possible that this is a
> case that it is missed.
>
> Does the same thing happen if you run outside of WinIDE?  Try running it

Yes, but see below.


> from a command-line window using python.exe so you can see any warning
> log messages that wxWidgets is issuing.  I seem to recall that WinIDE
> has a setting that causes it to stop on all exceptions, even if they are
> caught or cleared, perhaps changing that will help.
>
>
> >
> > I thought, that using too many wxTimer-s could cause this problem (other
> > controls used timers too to update themselves).
>
> Doubtful, unless you have dozens of timers.

Glad to here that. I'll unroll all my changes regarding timers. They are
really handy for having controls updating themselves.

>
> >
> > So I decided to eliminate all timers and to write an update method for
all
> > controls that should be able to update themselves. This update-method
were
> > then called from the MainFrames's on-idle-method. The rationale: No more
> > timers and only one on-idle-method.
> >
> > But that did not solve the problem. The same and sometimes other weired
> > errors popped up now in code called by OnGetItemAttr() ans
OnGetItemText()
> > of the virtual wxListCtrl.
> >
> > Example:
> >
> >    def __str__(self):
> >       if self._value: # <- "Inappropriate argument type: an integer is
> > required".
> >          return str(self._value)
> >       return ''
> >
> > Or this:
> >
> >    def OnGetItemAttr(self, item):
> >       if item == self.model().currentLineNbr(): # <- "Inappropriate
argument
> > type: an integer is
> >          return self._attr
> >       return None
> >
> >
> > Executing the offending line in the Debug Probe (yes, it's WingIDE) in
each
> > case passes w/o problems - weird. Looking at the stack data doesn't show
any
> > data corruption, everything seems okay.
>
> Because it probably happened in whatever weas executed before the error
> was detected.
>
> >
> > I commented out this and that and seem to have found out, that as soon
> > SetItemCount() is called, the control is no more able to do its job.
>
>
> Do you also implement OnGetItemImage?  Does it always return an integer?
>   (If you don't use an ImageList for this control then just return -1.)
>

That's it <face flushed red/>.

I had written:

def OnGetItemImage(self, item):
#    if item % 3 == 0:
#        return self.idx1
#    else:
#        return -1
    pass

Oh god, how embarrassing!

When I deleted the whole method, wxPython 2.5 threw a wxAssert stating, that
OnGetItemImage() shouldn't be called or something like that (can reproduce
that if there's interest on it). Anyway, overriding this method seems to be
a must. But with the right return value, of course...

So, writing

def OnGetItemImage(self, item):
    return -1

did it. Small cause, big effect.

Again, thanks a lot, Robin!

Kind regards
Franz GEIGER



> --
> Robin Dunn
> Software Craftsman
> http://wxPython.org  Java give you jitters?  Relax with wxPython!
>
>
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