Re: split-window-preferred-function

[martin rudalics <rudalics@gmx.at>]

 > 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.

In the first configuration below (for example, displaying a speedbar in
window 1) people might want to split window 2 horizontally

+---+-----------------------------------+
| 1 | 2                                 |
|   |                                   |
|   |                                   |
|   |                                   |
|   |                                   |
|   |                                   |
+---+-----------------------------------+

while in the next configuration horizontal splitting appears less
desirable:

+------------------+--------------------+
| 3                | 4                  |
|                  |                    |
|                  |                    |
|                  |                    |
|                  |                    |
|                  |                    |
+------------------+--------------------+

How would I express that without `split-width-threshold'?

 > 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.

Currently `display-buffer' would not split the left window vertically
because it is not full-width.  With `split-width-threshold'

	  && (WINDOW_FULL_WIDTH_P (XWINDOW (window)))

we could write something like

           (>= (window-width window) (/ split-width-threshold 2))

hence `split-width-threshold' would serve the dual role to allow
splitting a window horizontally when it's at least that wide and
vertically when it's at least half that wide (due to a preceding
horizontal split maybe).