Re: Add function to rotate/transpose all windows

[martin rudalics <rudalics@gmx.at>]

 > I can't quite get it to work, imagine this scinario:
 >
 > +-----+------+
 > | A   |__B___|
 > |     |  C   |
 > +-----+------+
 >
 > What the above split does is that is splits A, with refer B, and these
 > windows aren't really siblings.  So if I do pass the refer of A and B,
 > it should be from A's parent, but then when I pass B with refer (cons C
 > (B and C's parent)), won't it bug out since B's parent is being set twice?

I tell you what I'm doing here: Let's call P the original parent of A
and Q that of B and C.  The first split is a "first child" below split
with A as window to split and a cons of B and P as REFER.  The second
split is a "next sibling" left split with B as window to split and a
cons of C and Q as REFER.  Both splits are done with combination limit
set to t.

So 'split-window-internal' will not use the current parent of A in the
first split (which is nil anyway) but make a new parent which it sets to
P (since that is passed as second argument of REFER).

In the second split it will not use the current parent of A and B (which
is the already resurrected P) but again make a new parent which it sets
to Q (since that is passed as second argument of REFER).

So the parent of B is indeed set twice: When B is resurrected it is set
to P.  When C is resurrected it is set to Q and Q's parent is set to P.

'split-window-internal' makes a new parent window (which it resurrects
in the cases above immediately) when 'window-combination-limit' is
non-nil.  Setting that value up is done in window-rotate.el in the
following excerpt where 'window' is the window to split (first A and
then B in our case):

	    (let* ((prev (window-alist-prev window))
		   (limit (window-alist-combination-limit parent))
		   ;; Set 'window-combination-limit' to make sure
		   ;; that a new parent is created when WINDOW's
		   ;; previous sibling and WINDOW do not have the
		   ;; same parent.
		   (window-combination-limit
		    (or limit
			(not prev)
			(not (eq (window-alist-parent prev)
				 (window-alist-parent window)))))

Here 'prev' is the original previous sibling of 'window' and 'parent'
its original parent (P in the first split and Q in the second).  I set
'window-combination-limit' to t in the following cases:

- 'parent' already has its combination limit set in which case I have to
   preserve it

- 'window' has no previous sibling

- the original parent of 'prev' is not the original parent of 'window'.

In our example, neither A in the first split nor B in the second split
have a previous sibling so I set 'window-combination-limit' to t in both
cases.

BTW if you bind 'window-combination-limit' to t don't forget to reset
it's effect for the parent window via

(set-window-combination-limit parent limit)

right after the split.  Otherwise the parent window cannot be recombined
later on although that would be principally possible.

martin