bug#6130: 23.1; artist-mode spray-can malfunction

[martin rudalics <rudalics@gmx.at>]

 > Could you take a look at the existing callers to see how they would
 > react to receiving nil (instead of a frame), or a frame (as now), or an
 > error (instead of a frame)?

Daniel in his first post wrote that

   I also went ahead and searched the lisp/ tree for other places that
   looked risky -- that is, where a position object was assumed to hold a
   window in a context where there was no such guarantee. Nothing jumped
   out at me, but there could be any number of issues with third-party
   code.

so I think this has been taken care of already.

 >>> and/or deprecate it (in favor of a new posn-window-or-frame).
 >> That's what I had in mind.
 >
 > But that only makes sense if most callers of posn-window can (or would
 > like to) also handle a frame.

Then we have still another choice: Provide a function `posn-frame' and
have `posn-window' return nil when the first element is a frame.  This
would backfire for people who would like `posn-window' to always return
the first element of a position.

martin