bug#14233: 24.3; Don't constrain frame size to character multiples

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 23 Apr 2013 08:52:08 +0200
> From: martin rudalics <rudalics@gmx.at>
> CC: jan.h.d@swipnet.se, esabof@gmail.com, 14233@debbugs.gnu.org
> 
>  >> change_frame_size has no idea whether it is called for a text or a
>  >> graphical frame.
>  >
>  > That is done very easily, given the frame pointer (which
>  > change_frame_size accepts as its 1st argument).  E.g.:
>  >
>  >   if (FRAME_WINDOW_P (f))
>  >     /* do the GUI thing */
> 
> A couple of weeks ago I asked you whether HAVE_WINDOW_SYSTEM would be
> sufficient but got no answer :-( The problem is that I'm still not sure
> whether FRAME_WINDOW_P is sufficient.  At least in frame.c all
> FRAME_WINDOW_P calls are guarded by HAVE_WINDOW_SYSTEM checks as
> 
> #ifdef HAVE_WINDOW_SYSTEM
>        if (FRAME_WINDOW_P (XFRAME (this)))
> 	...
> #endif

That's because the members of 'struct frame' that are tested by
FRAME_WINDOW_P do not exist unless HAVE_WINDOW_SYSTEM is defined.
Emacs caters to TTY frames both in a build --without-x, where
HAVE_WINDOW_SYSTEM is not defined and none of the X code is compiled;
and in a build that does support GUI frames, but just created a
text-mode frame for some reason.  Thus the need to have the code both
ifdef'ed away at compile time and tested at run time.

> so some doubt remains whether this predicate is correctly installed on
> every platform.

There's no doubt: it is, as described above.

> In any case I'd want either an #ifdef or a simple and robust
> predicate without having to care about #ifdefs.

Sorry, you can't, not with the current infrastructure.  You must do it
with a predicate that is also protected with an ifdef.

>  >> Text frames might want to call it as before using character sizes.
>  >
>  > On text-mode frames, each character is one pixel.  Emacs knows that
>  > already.
> 
> In the past weeks I started to doubt whether Emacs really knows
> everything it pretends to know.

Maybe so, but "1 character == 1 pixel on TTY frames" does not belong
to any gray areas.

>  >> In any case, the callers have to strip space used for tool- or
>  >> menubars because change_frame_size does not know whether these are
>  >> part of the frame or not.
>  >
>  > Why can't change_frame_size know that?
> 
> The callers should know best whether a toolbar is part of their frames
> or not.  But we could obviously teach change_frame_size to check that.

I think all the information is already stored in the frame object.