bug#4147: 23.1.50: Info-search command strange behaviour

[martin rudalics <rudalics@gmx.at>]

 > I think no need to relay back because a keymap click in a "header-line"
 > window will call a function that updates `header-line-format' whose new
 > content will be displayed in this window anyway.

But you want to display the buffer the tab stands for in the other
window and not in the window where the tab appears.  That has to be
handled.

 > This means we need extra buffer per every header-line.

Yes.

 > I don't understand how do you intend to ensure that the tabbar
 > of the selected window doesn't disappear if the user types
 > `C-x 1' (`delete-other-windows')?

Windows code can investigate all sorts of window parameters - in the
present case there would be parameters like "nodelete", "noresize",
"nosplit" and "noother" say.  Now consider a configuration like this

  --------------------
| T                  |
|--------------------|
| W                  |
|                    |
|                    |
|                    |
|                    |
  --------------------

where T is the tabbar window and W the window (live or internal) the
tabbar is attached to.  These windows share a parent window which
doesn't contain any other window.


The tabbar window T would have

nodelete 'this ... the only way to delete T is via `delete-window' with
   T as argument or `delete-other-windows' with any but T or W as
   argument.  C-x 1 invoked with either T or W selected will fill the
   frame with T and W and delete all other windows.  C-x 0 in T deletes T
   but leaves W alone.

noresize 'vertical ... means T cannot be resized vertically.

nosplit 'parent ... means C-x 2 on T will split the parent window of T
   and W instead.

noother t ... means `other-window' will skip T.  There should be a
   special command to cycle through the attached windows of W and back to
   W though.  But `other-window' and its clients should not try to pick a
   window like T.


The window W would have

nodelete 'parent ... means C-x 0 in W will delete both T and W.  C-x 1
   in W means only W and T will be left on their frame.  We could add the
   twist that on a frame containing W and T only C-x 1 in W deletes T.

nosplit 'parent ... is as above.


Note that parameter values like 'parent are transitive so you can
attach, for example, another window on the left like:

  -------------------------
| S  | T                  |
|    |--------------------|
|    | W                  |
|    |                    |
|    |                    |
|    |                    |
|    |                    |
  -------------------------

and have C-x 0 in W delete S, T and W (provided there is another window
left), C-x 0 in S or T behave as usual, and C-x 1 in S, T or W delete
all windows but S, T and W.

martin