Re: PATCH: ewoc.el to permit node representation abutment

[Stefan Monnier]

> i've revised the patch (please see below) to handle empty representations.
> this was tested by modifying `cvs-fileinfo-pp' to output empty string for a
> certain hardcoded filename in my local repo, making the empty string
> conditional on a variable and toggling the variable followed by either
> `ewoc-refresh' or `ewoc-invalidate' calls.  (this description omits several
> steps for preparing the testing framework, but you get the idea.)

>       * emacs-lisp/ewoc.el (ewoc--create-node): Don't insert
>       trailing newline.  Also, create marker with insertion type t.
>       (ewoc--refresh-node): Delete all text from current node's
>       start marker to the next one's.  Also, make the marker
>       "stay put" before calling the pretty-printer, and return it.
>       (ewoc--init-stay-put-list, ewoc--reset-marker-types): New funcs.
>       (ewoc-create): Use marker insertion type t.
>       (ewoc-map): Collect "stay put" markers; reset them when done.
>       (ewoc-invalidate): Rewrite.
>       (ewoc-refresh): Don't insert newline.
>       Collect "stay put" markers; reset them when done.
>       (ewoc-set-hf): Reset header and footer markers when done.
>       * pcvs-info.el (cvs-fileinfo-pp): Insert trailing newline.

> note that ewoc.el is 1.19 from cvs.

Hmm... now it looks too complex to be installed before Emacs-22.
Can't it be done more simply.  Basically just do something like:
[ quality-control: this is guaranteed 100% untested ]

 (defun ewoc--refresh-node (pp node)
   "Redisplay the element represented by NODE using the pretty-printer PP.
 Set NODE's start marker's insertion type to nil and return it."
   (save-excursion
     (let* ((inhibit-read-only t)
            (m (ewoc--node-start-marker node))
            (n (ewoc--node-right node)))
       ;; First, remove the string from the buffer:
       (delete-region m (ewoc--node-start-marker n))
       ;; Calculate and insert the string.
       (goto-char m)
       ;; Temporarily change insertion type of the end marker so it is indeed
       ;; moved to the end.
       (set-marker-insertion-type (ewoc--node-start-marker n) t)
       (funcall pp (ewoc--node-data node))
       (set-marker-insertion-type (ewoc--node-start-marker n) nil)
       ;; Since our markers have insertion type nil (i.e. not "insert-before"),
       ;; all markers that were at position `m' are still at position `m',
       ;; including the ones for subsequent empty nodes, which we thus have
       ;; to reseat.
       (setq m (ewoc--node-start-marker n))
       (while (and (setq n (ewoc--node-right n))
                   (< (ewoc--node-start-marker n) m))
           (set-marker (ewoc--node-start-marker n) m))))))


-- Stefan