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

[Stefan Monnier <monnier@iro.umontreal.ca>]

> 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.

To be honest, I don't know what that means.  IIUC it means that most of
the code doesn't care if posn-window sometimes returns a frame.

It's wrong for posn-window to return a frame.  So are there callers that
actually rely on this wrong behavior?  Are there callers where returning
nil instead of a frame would be a problem?  Are there callers where
signaling an error instead of returning a frame would be a problem?

> This would backfire for people who would like `posn-window' to always
> return the first element of a position.

That's OK, in the sense that we don't care if people's feelings
are hurt.  But if it breaks existing packages it's more problematic.


        Stefan