Re: split-window-preferred-function

[Juri Linkov]

> I'm not yet sure how to handle the following two:
>
>                 || (NILP (XWINDOW (window)->parent))

As you can see, I already implemented this in
`split-window-preferred-horizontally' as a call
to `one-window-p'.

> BTW, do we want a `split-width-threshold'?

In my initial patch I presented the variable `split-width-threshold',
but in the final installed patch I dropped this variable,
because I realized that it is not necessary.

The reason is simple: there is no sense to have more than two
automatically horizontally split side-by-side windows.  For instance,
I use the smallest readable font and on a wide screen I get 200 columns.
Splitting them in three parts gives less than 80-column wide windows that
is not comfortable width to work in most buffers.

It is true that some specialized features like speedbar might
require a narrow window, but they can create such a window
configuration explicitly.  So really automatic splitting in
more than 3 horizontally split windows is not necessary.

However, what is very much necessary, and what is still missing in
`split-window-preferred-horizontally' is the ability to
split _vertically_ in horizontally split windows.

Let's take for example `calendar'.  When we have two horizontally split
windows and call `M-x calendar', it displays the calendar window
in the adjacent window.  This is very inconvenient because the
calendar window is usually not higher than 8 lines and the
rest of its window below is filled by empty space:

    +------------+------------+
    |            |            |
    |            |  calendar  |
    |            |            |
    |            |            |
    |            |            |
    |            |            |
    |            |            |
    |            |            |
    |            |            |
    |            |            |
    |            |            |
    |            |            |
    +------------+------------+

It would be more preferable for `calendar' to split the current window
vertically and adjust its height like it already does:

    +------------+------------+
    |            |            |
    |            |            |
    |            |            |
    |            |            |
    |            |            |
    |            |            |
    |            |            |
    |            |            |
    +------------+            |
    |            |            |
    |  calendar  |            |
    |            |            |
    +------------+------------+

I'm not sure yet whether this behavior can be generalized in
`split-window-preferred-horizontally' or `calendar' should
treat it specially.

-- 
Juri Linkov
http://www.jurta.org/emacs/