* calendar/todos.el: Improve handling of overlays.

(todos-get-overlay): New function.
(todos-prefix-overlay): Remove, since subsumed by
todos-get-overlay, and replace by the latter in callers.
(todos-reset-prefix): Apply only to buffer visiting Todos files.
Simplify implementation and use `todos' overlay property.
(todos-reset-done-separator): Use todos-get-overlay and `todos'
overlay property.  Fix logic.
(todos-category-select): Use todos-get-overlay and `todos' overlay
property.
(todos-remove-item): Use todos-get-overlay.  Correct obsolete code.
(todos-prefix-overlays): Use todos-top-priority face also for
non-numerical prefix of top priority items.  Add `todos' overlay
property.
(todos-hide-show-date-time): Simplify, using todos-get-overlay and
`todos' overlay property.

2 files changed, 98 insertions, 87 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 869a2f3deb7..2e4aac74190 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,22 @@
+2013-02-16  Stephen Berman  <stephen.berman@gmx.net>
+
+        * calendar/todos.el: Improve handling of overlays.
+        (todos-get-overlay): New function.
+        (todos-prefix-overlay): Remove, since subsumed by
+        todos-get-overlay, and replace by the latter in callers.
+        (todos-reset-prefix): Apply only to buffer visiting Todos files.
+        Simplify implementation and use `todos' overlay property.
+        (todos-reset-done-separator): Use todos-get-overlay and `todos'
+        overlay property.  Fix logic.
+        (todos-category-select): Use todos-get-overlay and `todos' overlay
+        property.
+        (todos-remove-item): Use todos-get-overlay.  Correct obsolete code.
+        (todos-prefix-overlays): Use todos-top-priority face also for
+        non-numerical prefix of top priority items.  Add `todos' overlay
+        property.
+        (todos-hide-show-date-time): Simplify, using todos-get-overlay and
+        `todos' overlay property.
+
 2013-02-14  Stephen Berman  <stephen.berman@gmx.net>
 
         * calendar/todos.el (todos-edit-multiline, todos-edit-quit):
diff --git a/lisp/calendar/todos.el b/lisp/calendar/todos.el
index e3bac9fb60a..13249f95c10 100644
--- a/lisp/calendar/todos.el
+++ b/lisp/calendar/todos.el
@@ -212,21 +212,14 @@ These reflect the priorities of the items in each category."
 (defun todos-reset-prefix (symbol value)
   "The :set function for `todos-prefix' and `todos-number-priorities'."
   (let ((oldvalue (symbol-value symbol))
-        (files (append todos-files todos-archives)))
+        (files todos-file-buffers))
     (custom-set-default symbol value)
     (when (not (equal value oldvalue))
       (dolist (f files)
         (with-current-buffer (find-file-noselect f)
-          (save-window-excursion
-            (todos-show)
-            (save-excursion
-              (widen)
-              (goto-char (point-min))
-              (while (not (eobp))
-                (remove-overlays (point) (point)); 'before-string prefix)
-                (forward-line)))
-            ;; Activate the new setting (save-restriction does not help).
-            (save-excursion (todos-category-select))))))))
+          (remove-overlays 1 (1+ (buffer-size)) 'todos 'prefix)
+          ;; Activate the new setting in the current category.
+          (save-excursion (todos-category-select)))))))
 
 (defcustom todos-item-mark "*"
   "String used to mark items.
@@ -1181,14 +1174,16 @@ done items are shown.  Its value is determined by user option
               (concat "\n\\(" (regexp-quote todos-category-done) "\\)") nil t)
         (let* ((beg (match-beginning 1))
                (end (match-end 0))
-               (ovs (overlays-at beg))
-               (ov (when ovs (car ovs)))
+               (ov (progn (goto-char beg)
+                          (todos-get-overlay 'separator)))
                (old-sep (when ov (overlay-get ov 'display)))
                new-ov)
-          (when (string= old-sep sep)
-            (setq new-ov (make-overlay beg end))
-            (overlay-put new-ov 'display todos-done-separator)
-            (delete-overlay ov)))))))
+          (when old-sep
+            (unless (string= old-sep sep)
+              (setq new-ov (make-overlay beg end))
+              (overlay-put new-ov 'todos 'separator)
+              (overlay-put new-ov 'display todos-done-separator)
+              (delete-overlay ov))))))))
 
 (defun todos-category-completions ()
   "Return a list of completions for `todos-read-category'.
@@ -1259,17 +1254,12 @@ Todos files named in `todos-category-completions-files'."
         ;; Make display overlay for done items separator string, unless there
         ;; already is one.
         (let* ((done-sep todos-done-separator)
-               (ovs (overlays-at done-sep-start))
-               ;; ov-sep0 ov-sep1)
-               ov-sep)
-          ;; There should never be more than one overlay here, so car suffices.
-          (unless (and ovs (string= (overlay-get (car ovs) 'display) done-sep))
-            (setq ov-sep (make-overlay done-sep-start done-end))
-            (overlay-put ov-sep 'display done-sep))))
-            ;; (setq ov-sep0 (make-overlay done-sep-start done-end))
-            ;; (setq ov-sep1 (make-overlay done-end done-end))
-            ;; (overlay-put ov-sep0 'invisible t)
-            ;; (overlay-put ov-sep1 'after-string done-sep)))
+               (ov (progn (goto-char done-sep-start)
+                          (todos-get-overlay 'separator))))
+          (unless ov
+            (setq ov (make-overlay done-sep-start done-end))
+            (overlay-put ov 'todos 'separator)
+            (overlay-put ov 'display done-sep))))
       (narrow-to-region (point-min) done-start)
       ;; Loading this from todos-mode, or adding it to the mode hook, causes
       ;; Emacs to hang in todos-item-start, at (looking-at todos-item-start).
@@ -1517,11 +1507,10 @@ The final element is \"*\", indicating an unspecified month.")
 
 (defun todos-remove-item ()
   "Internal function called in editing, deleting or moving items."
-  (let* ((beg (todos-item-start))
-         (end (progn (todos-item-end) (1+ (point))))
-         (ovs (overlays-in beg beg)))
-    ;; There can be both prefix/number and mark overlays.
-    (while ovs (delete-overlay (car ovs)) (pop ovs))
+  (let* ((end (progn (todos-item-end) (1+ (point))))
+         (beg (todos-item-start))
+         (ov (todos-get-overlay 'prefix)))
+    (when ov (delete-overlay ov))
     (delete-region beg end)))
 
 (defun todos-diary-item-p ()
@@ -1545,20 +1534,24 @@ The final element is \"*\", indicating an unspecified month.")
         (progn (goto-char (point-min))
                (looking-at todos-done-string-start)))))
 
-(defun todos-prefix-overlay ()
-  "Return this item's prefix overlay."
-  ;; Why doesn't this work?
-  ;; (get-char-property-and-overlay lbp 'before-string)
-  (let* ((lbp (line-beginning-position))
-         (ovs (overlays-in lbp lbp)))
-    (car ovs)))
+(defun todos-get-overlay (val)
+  "Return the overlay at point whose `todos' property has value VAL."
+  ;; Use overlays-in to find prefix overlays and check over two
+  ;; positions to find done separator overlay.
+  (let ((ovs (overlays-in (point) (1+ (point))))
+        ov)
+    (catch 'done
+      (while ovs
+        (setq ov (pop ovs))
+        (when (eq (overlay-get ov 'todos) val)
+          (throw 'done ov))))))
 
 (defun todos-marked-item-p ()
   "Non-nil if this item begins with `todos-item-mark'.
  In that case, return the item's prefix overlay."
   ;; If a todos-item-insert command is called on a Todos file before
   ;; it is visited, it has no prefix overlays, so conditionalize:
-  (let* ((ov (todos-prefix-overlay))
+  (let* ((ov (todos-get-overlay 'prefix))
          (pref (when ov (overlay-get ov 'before-string)))
          (marked (when pref
                    (string-match (concat "^" (regexp-quote todos-item-mark))
@@ -1571,7 +1564,7 @@ The final element is \"*\", indicating an unspecified month.")
   ;; Insertion pushes item down but not its prefix overlay.  When the
   ;; overlay includes a mark, this would now mark the inserted ITEM,
   ;; so move it to the pushed down item.
-  (let ((ov (todos-prefix-overlay))
+  (let ((ov (todos-get-overlay 'prefix))
         (marked (todos-marked-item-p)))
     (insert item "\n")
     (when marked (move-overlay ov (point) (point))))
@@ -1585,41 +1578,45 @@ The overlay's value is the string `todos-prefix' or with non-nil
 the number of todo or done items in the category indicating the
 item's priority.  Todo and done items are numbered independently
 of each other."
-  (let ((prefix (propertize (concat todos-prefix " ")
-                            'face 'todos-prefix-string))
-        (num 0)
+  (let ((num 0)
         (cat-tp (or (cdr (assoc-string
                           (todos-current-category)
                           (nth 2 (assoc-string todos-current-todos-file
                                                todos-priorities-rules))))
                     todos-show-priorities))
-        done)
+        done prefix)
     (save-excursion
       (goto-char (point-min))
       (while (not (eobp))
         (when (or (todos-date-string-matcher (line-end-position))
                   (todos-done-string-matcher (line-end-position)))
           (goto-char (match-beginning 0))
-          (when todos-number-priorities
-            (setq num (1+ num))
-            ;; Reset number to 1 for first done item.
-            (when (and (looking-at todos-done-string-start)
-                       (looking-back (concat "^"
-                                             (regexp-quote todos-category-done)
-                                             "\n")))
-              (setq num 1
-                    done t))
-            (setq prefix (propertize (concat (number-to-string num) " ")
-                                     'face
-                                     ;; Numbers of top priorities have
-                                     ;; a distinct face in Todos mode.
-                                     (if (and (not done) (<= num cat-tp)
-                                              (eq major-mode 'todos-mode))
-                                         'todos-top-priority
-                                       'todos-prefix-string))))
-          (let ((ov (todos-prefix-overlay))
+          (setq num (1+ num))
+          ;; Reset number to 1 for first done item.
+          (when (and (looking-at todos-done-string-start)
+                     (looking-back (concat "^"
+                                           (regexp-quote todos-category-done)
+                                           "\n")))
+            (setq num 1
+                  done t))
+          (setq prefix (concat (propertize
+                                (if todos-number-priorities
+                                    (number-to-string num)
+                                  todos-prefix)
+                                'face
+                                ;; Prefix of top priority items has a
+                                ;; distinct face in Todos mode.
+                                (if (and (not done) (<= num cat-tp)
+                                         (eq major-mode 'todos-mode))
+                                    'todos-top-priority
+                                  'todos-prefix-string))
+                               " "))
+          (let ((ov (todos-get-overlay 'prefix))
                 (marked (todos-marked-item-p)))
+            ;; Prefix overlay must be at a single position so its
+            ;; bounds aren't changed when (re)moving an item.
             (unless ov (setq ov (make-overlay (point) (point))))
+            (overlay-put ov 'todos 'prefix)
             (overlay-put ov 'before-string (if marked
                                                (concat todos-item-mark prefix)
                                              prefix))))
@@ -3764,26 +3761,21 @@ face."
   (save-excursion
     (save-restriction
       (goto-char (point-min))
-      (let ((ovs (overlays-in (point) (1+ (point))))
-            ov hidden)
-        (while ovs
-          (setq ov (pop ovs))
-          (if (equal (overlay-get ov 'display) "")
-              (setq ovs nil hidden t)))
+      (if (todos-get-overlay 'header)
+          (remove-overlays 1 (1+ (buffer-size)) 'todos 'header)
         (widen)
         (goto-char (point-min))
-        (if hidden
-            (remove-overlays (point-min) (point-max) 'display "")
-          (while (not (eobp))
-            (when (re-search-forward
-                   (concat todos-date-string-start todos-date-pattern
-                           "\\( " diary-time-regexp "\\)?"
-                           (regexp-quote todos-nondiary-end) "? ")
-                   nil t)
-              (unless (save-match-data (todos-done-item-p))
-                (setq ov (make-overlay (match-beginning 0) (match-end 0) nil t))
-                (overlay-put ov 'display "")))
-            (todos-forward-item)))))))
+        (while (not (eobp))
+          (when (re-search-forward
+                 (concat todos-date-string-start todos-date-pattern
+                         "\\( " diary-time-regexp "\\)?"
+                         (regexp-quote todos-nondiary-end) "? ")
+                 nil t)
+            (unless (save-match-data (todos-done-item-p))
+              (setq ov (make-overlay (match-beginning 0) (match-end 0) nil t))
+              (overlay-put ov 'todos 'header)
+              (overlay-put ov 'display "")))
+          (todos-forward-item))))))
 
 (defun todos-mark-unmark-item (&optional n)
   "Mark item with `todos-item-mark' if unmarked, otherwise unmark it.
@@ -3794,7 +3786,7 @@ marking of the next N items."
   (dotimes (i n)
     (let* ((cat (todos-current-category))
            (marks (assoc cat todos-categories-with-marks))
-           (ov (todos-prefix-overlay))
+           (ov (todos-get-overlay 'prefix))
            (pref (overlay-get ov 'before-string)))
       (if (todos-marked-item-p)
           (progn
@@ -3817,7 +3809,7 @@ marking of the next N items."
     (while (not (eobp))
       (let* ((cat (todos-current-category))
              (marks (assoc cat todos-categories-with-marks))
-             (ov (todos-prefix-overlay))
+             (ov (todos-get-overlay 'prefix))
              (pref (overlay-get ov 'before-string)))
         (unless (todos-marked-item-p)
           (overlay-put ov 'before-string (concat todos-item-mark pref))
@@ -3834,7 +3826,7 @@ marking of the next N items."
     (while (not (eobp))
       (let* ((cat (todos-current-category))
              (marks (assoc cat todos-categories-with-marks))
-             (ov (todos-prefix-overlay))
+             (ov (todos-get-overlay 'prefix))
              (pref (overlay-get ov 'before-string)))
         (when (todos-marked-item-p)
           (overlay-put ov 'before-string (substring pref 1))
@@ -4883,7 +4875,7 @@ the format of Diary entries."
   (interactive)
   (widen)
   (todos-edit-mode)
-  (remove-overlays) ; nil nil 'before-string)
+  (remove-overlays)
   (message "%s" (substitute-command-keys
                  (concat "Type \\[todos-edit-quit] to check file format "
                          "validity and return to Todos mode.\n"))))
@@ -5412,7 +5404,7 @@ meaning to raise or lower the item's priority by one."
         (todos-insert-with-overlays item)
         ;; If item was marked, restore the mark.
         (and marked
-             (let* ((ov (todos-prefix-overlay))
+             (let* ((ov (todos-get-overlay 'prefix))
                     (pref (overlay-get ov 'before-string)))
                (overlay-put ov 'before-string (concat todos-item-mark pref)))))))