Re: Proposal: window-system-version function

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 22 May 2012 09:51:18 +0400
> From: Dmitry Antipov <dmantipov@yandex.ru>
> CC: emacs-devel@gnu.org

This probably becomes a moot point, given Stefan's response, but...

> On 05/21/2012 08:20 PM, Eli Zaretskii wrote:
> 
> > Thanks.  However, this change breaks backward compatibility.  Perhaps
> > it would be better to leave the variable alone, and _add_ the
> > function; that would be backward-compatible.
> 
> I fixed Lisp code in lisp/international/mule-diag.el and
> lisp/textmodes/artist.el; not sure about external packages which
> may also use it.

I'm not sure either, but gray hair tells me they might.

> Leaving the variable "as is" means that window-system-version
> and (window-system-version) may have different values, which
> is confusing.

Not confusing at all, since we would deprecate the variable.  But
breaking working code over such a minor issue is not a good idea, IMO.

> Ideally, window-system-version should be a frame-local
> variable, but I'm wondering whether this is possible in Emacs.

Yes, see "Frame Parameters".

> >> +It's value is a number:
> >> + - 0 for a termcap frame,
> >> + - Major X protocol version for the frame on X display,
> >> + - Major OS version for the frame on MS-Windows display,
> >> + - 24 for the frame on direct-write MS-DOS display,
> >> + - 10 for the frame on a GNUstep or Macintosh Cocoa display.
> >
> > This is inaccurate at least for MS-DOS and MS-Windows.  Do we really
> > want to document the precise meaning of the values here?  Why is that
> > important?
> 
> I'm not sure about exact values on a systems beyond *nix, and I suppose
> that every Lisp-visible function should be documented.

I didn't mean not to document it.  I meant to document it like this:

 Value is the version of the windowing system used for this frame, as
 a string.

I think this is enough, since the number itself won't tell anything
specific anyway.

> >> +#ifdef HAVE_X_WINDOWS
> >> +    case output_x_window:
> >> +      return make_number (ProtocolVersion (FRAME_X_DISPLAY (f)));
> >> +#endif
> >> +#ifdef WINDOWSNT
> >> +    case output_w32:
> >> +      return make_number (w32_major_version);
> >> +#endif
> >> +#ifdef MSDOS
> >> +    case output_msdos_raw:
> >> +      return make_number (24);
> >> +#endif
> >
> > The MSDOS build supports HAVE_X_WINDOWS as well, so HAVE_X_WINDOWS and
> > MSDOS are not by themselves mutually exclusive.
> 
> The cpp stuff above has no mutually exclusive paths (no #elif or so),
> so it should work if both HAVE_X_WINDOWS and MSDOS are defined.

Right, my bad.  I've misread the code.