bug#21100: 25.0.50; quit-restore-window should also retore width, not just height

[martin rudalics]

> This was from emacs -Q. On my machine (running Ubuntu), with a
> maximized frame,

emacs -Q doesn't start in a maximized frame.

> increasing the font-size doesn't make the frame
> larger. Maybe it's a difference in the OS (I think on Windows if you
> increase font-size the frame does get enlarged).

Not if it's maximized.  I spent some time on the code handling that.

> The point is that the combination of font-size and frame-size has to
> be such that two windows do not fit side-by-side. In this situation,
> Emacs usually creates temp windows below the current window (instead
> of to the right).

I have no problem resizing my frame so it makes either a new window on
the bottom or on the right.  The problem is that you are talking about
_reusing_ a window on the bottom or the right.

> Here's a new recipe to verify what I'm explaining
> now.
>
> 0. Start emacs -Q
> 1. Resize the frame so that it is less than 30 columns wide, and at
> least 30 lines tall.
> 2. Type `C-h f point RET'.
> 3. The temp window is created below.
>
> Now here is an updated recipe for the original behavior I was
> describing (the fact that windows are vertically expanded to fit the
> help buffer).
>
> 0. Start emacs -Q
> 1. Resize the frame so that it is less than 30 columns wide, and at
> least 30 lines tall.
> 2. Type `C-- C-5 C-x C-2', to create a tiny window below.
> 2. Type `C-h f point RET'.
> 3. The temp buffer is displayed in the window you had created, and the
> windows size is increased to half the frame.

Now I understand.  This resizing is due to `even-window-heights' being
non-nil by default.  If you set that to nil, no resizing is done.  Also,
with more than two windows, you get no resizing either.  This is a very
old option, introduced some time before automatic side-by-side splitting
was introduced.

> 4. If you hit q on that help window, it will return to the original
> height of 5 lines.

Funny.  I never even tested that.

>> It's just that I don't know _why_ a reused window would be expanded.
>> Can you point me to where in the code this expansion takes place?
>
> Some edebugging shows me it is done by
> `display-buffer-use-some-window', and indeed I see a `window-resize'
> in there.

The re-resizing should occur in `quit-restore-window' on this line:

            (window-resize window (- (nth 3 quad) (window-total-height window)))

Please check.

So what you probably want is a new option `even-window-widths' (or maybe
`even-window-sizes') which, if non-nil, does for side-by-side splits the
same thing `even-window-heights' does for a below split.  And,
obviously, `quit-restore-window' should be able to size it back (I have
written this part already).  Suggestions welcome.

martin