Re: MY window tree!

[Lennart Borgman (gmail)]

martin rudalics wrote:
>  > If not so, then do I not have to look at all overlays in all buffers?
>
> You should look only at the overlays of buffers whose windows have
> "changed".  That is, all buffers where a ovlwin-window association
> exists such that window displays the buffer.
>
> I think that after running winsav to its end you have four cases:
>
>   The window existed before and exists now.  Ignore it. It's the same
>   window and any overlays referencing it before still reference it.
>
>   The window did not exist before but exists now.  Since you do not
>   arbitrarily create new windows there must be a ovlwin-window
>   association and the associated buffer's overlays may have to be
>   updated.
>
>   The window existed before and doesn't exist now (probably because it
>   was discarded during splitting).  Ignore it.  Any overlay referencing
>   that window won't be displayed in any other window.
>
>   The window didn't exist before and doesn't now.  Ignore it trivially.


Maybe you are saying something that I am missing, but I believe I am 
doing what you propose already. Some questions/points to see if we agree:

1) I think I must search all buffers
2) I must check all overlays in these buffers
3) The only thing I have to check in the overlays is the 'window prop
4) I only have to care if the prop value is a window in the saved tree
5) If that window is not on a frame any more I just replace the value
6) Otherwise I make a new overlay -- seldom

The above is what I am doing. Is any of those points incorrect in your 
opinion? Here is the code:

    (dolist (buf (buffer-list))
      (with-current-buffer buf
        (save-restriction
          (widen)
          (dolist (overlay (overlays-in (point-min) (point-max)))
            (when (setq ovlwin (car (memq (overlay-get overlay 'window) 
oldwins)))
              (setq window (cadr (assoc ovlwin win-list)))
              ;; If the old window is still alive then copy overlay,
              ;; otherwise change the 'window prop.
              (if (not (and (window-live-p ovlwin)
                            (window-frame ovlwin)))
                   ....

`oldwins' is a list with the old windows, ie the windows in the saved tree.

> Initially you didn't want to bother about overlays at all, now you want
> to check overlays in all buffers.  

True, I was not aware of that they could point to windows.

> Initially you wanted to convince me
> that you can do it in Lisp, now that you have nearly done it, you favor
> a solution in C.  

In the short term I think this solution is good enough. And it actually 
can do a bit more than a solution in C that gives handles to manipulate 
the internal C window tree.

> Alas, this will be hardly ever done in C, the window
> related code is too hairy.  


I believe it would be possible to right code to manipulate the internal 
tree as above. A solution building on that would probably use the 
resizing part from my elisp solution (or something similar).

> Yours could be perfect (if you just removed
> the make-overlay stuff).

It could be Good Enough ;-)