Function: ewoc-locate

ewoc-locate is a byte-compiled function defined in ewoc.el.gz.

Signature

(ewoc-locate EWOC &optional POS GUESS)

Documentation

Return the node that POS (a buffer position) is within.

POS may be a marker or an integer. It defaults to point. GUESS should be a node that it is likely to be near POS.

If POS points before the first element, the first node is returned. If POS points after the last element, the last node is returned. If the EWOC is empty, nil is returned.

View in manual

Source Code

;; Defined in /usr/src/emacs/lisp/emacs-lisp/ewoc.el.gz
(defun ewoc-locate (ewoc &optional pos guess)
  "Return the node that POS (a buffer position) is within.
POS may be a marker or an integer.  It defaults to point.
GUESS should be a node that it is likely to be near POS.

If POS points before the first element, the first node is returned.
If POS points after the last element, the last node is returned.
If the EWOC is empty, nil is returned."
  (unless pos (setq pos (point)))
  (ewoc--set-buffer-bind-dll ewoc

    (cond
     ;; Nothing present?
     ((eq (ewoc--node-nth dll 1) (ewoc--node-nth dll -1))
      nil)

     ;; Before second elem?
     ((< pos (ewoc--node-start-marker (ewoc--node-nth dll 2)))
      (ewoc--node-nth dll 1))

     ;; After one-before-last elem?
     ((>= pos (ewoc--node-start-marker (ewoc--node-nth dll -2)))
      (ewoc--node-nth dll -2))

     ;; We now know that pos is within an elem.
     (t
      ;; Make an educated guess about which of the three known
      ;; node'es (the first, the last, or GUESS) is nearest.
      (let* ((best-guess (ewoc--node-nth dll 1))
	     (distance (abs (- pos (ewoc--node-start-marker best-guess)))))
	(when guess
	  (let ((d (abs (- pos (ewoc--node-start-marker guess)))))
	    (when (< d distance)
	      (setq distance d)
	      (setq best-guess guess))))

	(let* ((g (ewoc--node-nth dll -1))	;Check the last elem
	       (d (abs (- pos (ewoc--node-start-marker g)))))
	  (when (< d distance)
	    (setq distance d)
	    (setq best-guess g)))

	(when (ewoc--last-node ewoc)    ;Check "previous".
	  (let* ((g (ewoc--last-node ewoc))
		 (d (abs (- pos (ewoc--node-start-marker g)))))
	    (when (< d distance)
	      (setq distance d)
	      (setq best-guess g))))

	;; best-guess is now a "best guess".
	;; Find the correct node. First determine in which direction
	;; it lies, and then move in that direction until it is found.

	(cond
	 ;; Is pos after the guess?
	 ((>= pos
	      (ewoc--node-start-marker best-guess))
	  ;; Loop until we are exactly one node too far down...
	  (while (>= pos (ewoc--node-start-marker best-guess))
	    (setq best-guess (ewoc--node-next dll best-guess)))
	  ;; ...and return the previous node.
	  (ewoc--node-prev dll best-guess))

	 ;; Pos is before best-guess
	 (t
	  (while (< pos (ewoc--node-start-marker best-guess))
	    (setq best-guess (ewoc--node-prev dll best-guess)))
	  best-guess)))))))