bug#22009: PATCH: Use `window-total-width' in `window-splittable-p'

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 26 Nov 2015 19:06:07 +0100
> From: martin rudalics <rudalics@gmx.at>
> CC: joostkremers@fastmail.fm, 22009@debbugs.gnu.org
> 
>  >> Note that ‘window-splittable-p’ is exclusively used by ‘display-buffer’
>  >> and the probability is very high that the new window will not be used
>  >> for displaying the buffer of the original window.  The new window will
>  >> very likely have its own margins and header line.
>  >
>  > Is it forbidden to call that function from any other Lisp?  If so,
>  > disregard what I wrote.  But if not, window-splittable-p should do a
>  > correct job no matter who calls it, do you agree?
> 
> Presently ‘window-splittable-p’ is misnamed and I think that's the main
> cause of the confusion.  But its doc-string clearly names
> ‘split-window-sensibly’ as the caller (which is misnamed as well but all
> of these were written before ‘display-buffer’ was reorganized).  In any
> case both functions belong exclusively to ‘display-buffer’ and are not
> related to C-x 3.
> 
>  > My text that you quoted here talks about the "normal" case, where the
>  > margins stay put upon splitting windows.  I'm saying that in such a
>  > situation a decision made using the total width could be terribly
>  > wrong.
> 
> But the "normal" case where this happens is C-x 3 and there the mode
> that created the large margins should adapt.
> 
>  >> ‘window-min-width’ (and all related variables and functions) refer to
>  >> the total width of windows.  Changing its semantics would constitute
>  >> quite some effort.
>  >
>  > If it's complicated, let's do that on master.  But do it we must, IMO.
> 
> Basically it would amount to ‘split-window-horizontally’ telling us that
> it can't split the window.  Which might not be the intention of the user
> who expects the margins (whose sole purpose is to center the text in the
> window) to shrink accordingly.
> 
> But honestly I don't know which implications changing the semantics of
> ‘window-min-width’ could have.  I could imagine adding a new option say
> ‘window-min-text-width’ and have the resizing routines respect this as
> far as possible.

Maybe we should step back and recall what problem are we trying to
solve with the proposed patch, then.

>  >>   > The modes that triggered this are special in that they adapt their
>  >>   > margins to the split, but how would window-splittable-p know that?
>  >>   > Perhaps such modes should override that function, or maybe we should
>  >>   > provide a hook for them?
>  >>
>  >> This is not mode-triggered.
>  >
>  > In my text, "this" referred to this bug report.
> 
> If you mean that a mode introducing large margins should override
> ‘split-window-sensibly’ then this is not TRT.  ‘split-window-sensibly’
> is user territory and ‘window-splittable-p’ too.

Didn't you just tell they are called by display-buffer?  How's that
"user territory"?