Re: Black PNG Problem Resolved - 1 Problem Left

[Owen Taylor <otaylor redhat com>]

Michael ROGERS <M.Rogers@cs.ucl.ac.uk> writes:

> >Well... it looks like I got that black PNG background problem resolved. Thanks
> >go out to all who helped me out - there were some _old_ (1.0.97) PNG libs in
> >/lib that were causing all the trouble. My new GNOME desktop is very nice, but
> >there's one thing that still doesn't work: The Window Manager control panel
> >applet. It just doesn't show up. Is this a bug, or another one of my dumb
> >problems?
> 
> This happens when you don't have any window manager desktop files in
> ~/.gnome/wm-properties/. I'd definitely call it a bug, because if you don't
> have any entries for WMs you can't add one! This is only a problem if you
> don't have E, WindowMaker or Icewm installed. If you have one of those three 
> you can use the command "export WINDOW_MANAGER=icewm" (for example) before 
> running Gnome. If (like me) you don't have any of them installed, create a
> directory called wm-properties in ~/.gnome and copy one of the desktop files
> from the control-center package into it. Now the right-hand pane will appear
> (even though there still aren't any *valid* entries), and you can add an
> entry for your favourite WM.
> 
> I'll have a go at patching the wm-properties-capplet over the weekend unless
> someone can tell me why this "feature" exists.

It is not a "feature", it is a bug, and a fix would
be appreciated.

_However_, note that it is a design flaw, not a stupid oversight, and
I will not accept any patches that do not fix the design flaw,
because any patch that hacks around the problem is going
to break the carefully constructed current logic.

The design flaw is that the logic in the WM-properties capplet assumes
that it has a list of window managers and one of them
will be the currently selected window manager; so it has no
concept that there is no window manager or the current
window manager is unknown.

To fix the problem, the concept that none of the window
managers has to be added to the code, and someone
needs to figure out what happens, for instance, when

 1) There is no selected window manager (but the person
    actually is running, say, twm, which the capplet
    is unaware of)
 2) Somebody selects a window manager and hits "try"
 3) They then hit "Revert"

Killing the current window manager and leaving the
user with no window manager is not an option, so you
probably need to just leave window manager 
that was "tried" running, but pretend that you've
reverted.

But, if you want to go that route, then consider what
happens if the window manager that the user tried
to "Try" failed to start at all. Currently, the
window manager capplet will try to do an automatic
revert. So, you need to go straight to the 
scary dialog which says:

 "Could not start fallback window manager.\n"
 "Please run a window manager manually. You can\n"
 "do this by selecting \"Run Program\" in the\n"
 "foot menu\n"

That's not very pretty... you might want to
put a button on that dialog to try and run
twm ... which would be better than no wm.

Anyways, the point here is that I would not recommend 
hacking too much in the wm properties code without 
taking some time to understand what is going on in there.

Regards,
                                        Owen