Re: [dev] [dwm] BadAtom error solved

From: pod <pod_AT_nervous-energy.org.uk>
Date: Thu, 27 Oct 2011 00:05:26 +0100

>>>>> "CH" == Christoph Helma <helma_AT_in-silico.ch> writes:

    CH> Thanks! Changing that line to

    CH> Atom wmProperty = XInternAtom(display->get(), "WM_HINTS", True);
    
    CH> seems to solve the problem.

... and almost certainly introduces an entirely different sort of
problem.

I don't think WM_HINTS and _MOTIF_WM_HINTS are at all the same thing.

What you have done merely appears to work because WM_HINTS almost
certainly already exists in the server, thus XInternAtom(..., True) is
pretty much certain to return XA_WM_HINTS (35, the predefined atom
number for WM_HINTS) and not None.

However, the value of a WM_HINTS property is intended to have a specific
structure that is certainly not the same structure as the Hints struct
value that is now being set in the subsequent XChangeProperty() call.

As Anselm hinted probably what you ought to do is change the last
argument in that call to XInternAtom() from True to False. That ought
to mean that if the _MOTIF_WM_HINTS atom does not already exist in the
server then it is created and an atom number (and not the value None) is
returned for it. This atom number should then be valid for use in the
subsequent XChangeProperty(). I'm afraid I can't comment on whether the
structure value as given by the Hints struct is in fact appropriate for
a _MOTIF_WM_HINTS property.

By leaving that last argument as True and not checking wmProperty==None
after the XInternAtom() call you in fact still have precisely the same
bug. It is just now much less likely (maybe even impossible, when
talking to a normally functioning X server) to occur.
Received on Thu Oct 27 2011 - 01:05:26 CEST