[O] [PATCH] Implement priority inheritance for agenda views.

[Michael Hohmuth]

* lisp/org.el (org-use-prio-inheritance): New customizable for using
priority inheritance in agenda views.  Defaults to off
(org-get-priority-char): Factored out from org-get-priority.  Return
priority token from headline, defaulting to an optional fallback or
org-default-priority.
(org-get-priority): Use org-get-priority-char. Default to an optional
fallback or org-default-priority.
(org-scan-tags): Assign and display priority according to
org-use-prio-inheritance.
---
This patch can be pulled from branch prio-inherit at
git://github.com/altruizine/org-mode.git .

I am aware that priority inheritance for to-do items has been
requested and rejected in the past, on the grounds of inherited
priorities allegedly inflating the number of assigned priorities,
thereby defeating the purpose of priorities.  Well, I disagree, as I
have found inherited priorities useful in practice.

The code changes are relatively minor, with explicit tracking of the
priority tag for each level, and pasting in this tag into the agenda
items when the inherited priority differs from the default priority.

Comments welcome!
Michael

PS: An FSF copyright-assignment process is in progress.

 lisp/org.el |   55 +++++++++++++++++++++++++++++++++++++++++++------------
 1 files changed, 43 insertions(+), 12 deletions(-)

diff --git a/lisp/org.el b/lisp/org.el
index cdf48c1..72a23f7 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -2498,6 +2498,14 @@ command used) one higher or lower that the default 
priority."
   :group 'org-priorities
   :type 'boolean)
 
+(defcustom org-use-prio-inheritance nil
+  "Non-nil means priority in levels apply also for sublevels.
+When nil, only the priority directly given in a specific line apply there."
+  :group 'org-priorities
+  :type '(choice
+         (const :tag "Not" nil)
+         (const :tag "Always" t)))
+
 (defcustom org-get-priority-function nil
   "Function to extract the priority from a string.
 The string is normally the headline.  If this is nil Org computes the
@@ -12332,15 +12340,20 @@ ACTION can be `set', `up', `down', or a character."
        (message "Priority removed")
       (message "Priority of current item set to %s" news))))
 
-(defun org-get-priority (s)
-  "Find priority cookie and return priority."
+(defun org-get-priority-char (s &optional fallback)
+  "Return priority cookie as char. Defaults to FALLBACK or, if that's
+unset, to org-default-priority."
+  (save-match-data
+    (if (string-match org-priority-regexp s)
+       (string-to-char (match-string 2 s))
+      (or fallback org-default-priority))))
+
+(defun org-get-priority (s &optional fallback)
+  "Find priority cookie and return priority. Defaults to FALLBACK or, if that's
+unset, to org-default-priority."
   (if (functionp org-get-priority-function)
       (funcall org-get-priority-function)
-    (save-match-data
-      (if (not (string-match org-priority-regexp s))
-         (* 1000 (- org-lowest-priority org-default-priority))
-       (* 1000 (- org-lowest-priority
-                  (string-to-char (match-string 2 s))))))))
+    (* 1000 (- org-lowest-priority (org-get-priority-char s fallback)))))
 
 ;;;; Tags
 
@@ -12393,8 +12406,9 @@ only lines with a TODO keyword are included in the 
output."
         (org-map-continue-from nil)
          lspos tags tags-list
         (tags-alist (list (cons 0 org-file-tags)))
+        (prio-alist (list (cons 0 org-default-priority)))
         (llast 0) rtn rtn1 level category i txt
-        todo marker entry priority)
+        todo marker entry priority prio-char)
     (when (not (or (member action '(agenda sparse-tree)) (functionp action)))
       (setq action (list 'lambda nil action)))
     (save-excursion
@@ -12409,8 +12423,18 @@ only lines with a TODO keyword are included in the 
output."
          (goto-char (setq lspos (match-beginning 0)))
          (setq level (org-reduced-level (funcall outline-level))
                category (org-get-category))
-         (setq i llast llast level)
+         (setq txt (org-get-heading))
+
+         (when org-use-prio-inheritance
+           ;; remove prio from same and sublevels
+           (while (>= (caar prio-alist) level)
+             (pop prio-alist))
+           ;; add this prio
+           (setq prio-char (org-get-priority-char txt (cdar prio-alist)))
+           (push (cons level prio-char) prio-alist))
+
          ;; remove tag lists from same and sublevels
+         (setq i llast llast level)
          (while (>= i level)
            (when (setq entry (assoc i tags-alist))
              (setq tags-alist (delete entry tags-alist)))
@@ -12469,21 +12493,28 @@ only lines with a TODO keyword are included in the 
output."
            (cond
             ((eq action 'sparse-tree)
              (and org-highlight-sparse-tree-matches
-                  (org-get-heading) (match-end 0)
+                  txt (match-end 0)
                   (org-highlight-new-match
                    (match-beginning 0) (match-beginning 1)))
              (org-show-context 'tags-tree))
             ((eq action 'agenda)
+             ;; paste in inherited priority tag if different from
+             ;; default priority
+             (when (and org-use-prio-inheritance
+                        (not (equal (org-get-priority-char txt) prio-char)))
+               (setq txt (replace-regexp-in-string "\\( \\).*\\'" 
+                             (concat " [#" (char-to-string prio-char) "] ")
+                             txt nil nil 1)))
              (setq txt (org-format-agenda-item
                         ""
                         (concat
                          (if (eq org-tags-match-list-sublevels 'indented)
                              (make-string (1- level) ?.) "")
-                         (org-get-heading))
+                         txt)
                         category
                         tags-list
                         )
-                   priority (org-get-priority txt))
+                   priority (org-get-priority txt prio-char))
              (goto-char lspos)
              (setq marker (org-agenda-new-marker))
              (org-add-props txt props
-- 
1.7.3.4