Re: undo in loaddefs.el buffer

[Jan D.]

Luc Teirlinck wrote:

> Do `emacs -q', M-x ielm then:
>
> (let (last-nonmenu-event) (yes-or-no-p "prompt"))
>
> Now if you press any key, regular or modifier, say "a", Control,
> Shift, nil is returned, like if you answered "No".  This appears to be
> an obvious bug.  For the particular application we are worried about,
> this is particularly bad, because "No" is the dangerous answer, the
> one that might make Emacs crash.
>  

The behaviour to pop down on key press is present in CVS and 21.3.  But 
this should only happen if the focus is on the frame and not the 
dialog.  It also only happens for Lucid and Lesstif/Motif dialogs.  The 
reason for this being in CVS is because it is in 21.3 :-).  Personally I 
think it is a strange behaviour.

However, I obviously did a typo when making the "pop down on ESC" (see 
below), so the Lucid pops down on any keypress when focus is on the 
dialog.  This is now fixed.

> If we repeat the experiment in 21.3, we see that the bug is not
> present there.  However, there is another bug.  If we click the mouse
> anywhere inside the Emacs frame, but outside the "Yes" button, nil is
> returned.  This is also a bug, which does _not_ occur in current CVS.
> This seems to be a case of introducing one bug by fixing another

This way of popping down the dialog has been replaced by popping down by 
pressing ESC, which is more in line with what other applications and 
toolkits use.  But the non-toolkit build uses menus instead of dialogs, 
so the behaviour is different.  For popup menus, clicking outside means 
"cancel" so in that case it is popped down.  The ESC thing was not 
implemented for the non-toolkit build, I guess I thought it wasn't that 
many people that used it and thus not worth it.

So in CVS, dialogs does not pop down because of a click outside the 
dialog.  The non-toolkit build is not a dialog but a menu, so it does 
pop down.

ESC shall pop down dialogs, except for the non-toolkit build (not 
implemented, but easy to add).

Any key pressed when the focus is on the Emacs frame and not the dialog 
pops down the Lucid and Lesstif/Motif dialog, to be compatible with 
21.3.  GTK and non-toolkit does not pop down on keypress outside the 
dialog/menu.

   Jan D.