Re: Best way to implement Keywords feature

[Martin Pohlack <mp26@os.inf.tu-dresden.de>]

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Hi All,

Martin Pohlack wrote:
> Alan E. Davis wrote:
>> In some cases, a single headword entry can relate to a large number of
>> topics.  I have tried dealing with longer tag lists: automatic
>> adjustment of tags column (on this list a little utility was posted:
>> org-adjust-tags-column-reset-tags.  I THINK that a keyword list may
>> allow more freedom to cross-index, especially if it is easy to use.
>>
>> Can someone suggest a way to implement a keywording system, perhaps with
>> a custom agenda search?  Or have others dealt with this issue in
>> innovative ways?
>>
>> I would appreciate any ideas.
> 
> I still have the feeling that tags are the way to go.  Searching etc.
> already works with tags.  Their disadvantage seems to be that lines get
> cluttered if many tags are used.
> 
> Maybe this can be solved with two approaches:
> * In agendas, one could have a filter for which tags to show / hide.
>   This would be useful otherwise too, as it would allow to hide context
>   tags in already defined agendas.
> 
>   org-agenda-hide-tags-regex
> 
>   For example, all my contexts start with "@", so I would set it to be
>   "^@work$" to hide redundant information in my work agendas, or use
>   "^@" to remove all context information from a specific agenda.
> 
> * For plain view, could we have a soft newline between tags and content
>   for an item (like in long-lines-mode)?
>   Tags would be shown on a new line (with indentation etc.) but would be
>   stored on the same line in files?
> 
>   For example, the file content ("\" added by me, should be one long
>   line):

Please find attached a patch that implements tag filtering for agenda views.

Feedback welcome.

Cheers,
Martin

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diff --git a/lisp/org-agenda.el b/lisp/org-agenda.el
index 708b193..e146bc0 100644
--- a/lisp/org-agenda.el
+++ b/lisp/org-agenda.el
@@ -1202,6 +1202,14 @@ When non-nil, this must be the number of minutes, e.g. 60 for one hour."
   :group 'org-agenda-line-format
   :type 'boolean)
 
+(defcustom org-agenda-hide-tags-regexp nil
+  "Regular expression used to fitler away specific tags in agenda views.
+Nil means hide no tags."
+  :group 'org-agenda-line-format
+  :type '(choice
+	  (const  :tag "Hide none" nil)
+	  (string :tag "Regexp   ")))
+
 (defcustom org-agenda-remove-tags nil
   "Non-nil means, remove the tags from the headline copy in the agenda.
 When this is the symbol `prefix', only remove tags when
@@ -4507,9 +4515,20 @@ Any match of REMOVE-RE will be removed from TXT."
   (save-match-data
     ;; Diary entries sometimes have extra whitespace at the beginning
     (if (string-match "^ +" txt) (setq txt (replace-match "" nil nil txt)))
-    (when org-agenda-show-inherited-tags
-      ;; Fix the tags part in txt
-      (setq txt (org-agenda-add-inherited-tags txt tags)))
+    ;; filter tags here
+    (when org-agenda-hide-tags-regexp
+      (setq tags (apply 'append (mapcar
+                                 (lambda (x)
+                                   (if (string-match org-agenda-hide-tags-regexp x)
+                                       nil
+                                     (list x)))
+                                 tags))))
+    ;; Fix the tags part in txt
+    (if org-agenda-show-inherited-tags
+        (setq txt (org-agenda-add-inherited-tags txt tags))
+      (when org-agenda-hide-tags-regexp
+        (setq txt (org-agenda-add-local-tags txt tags))))
+    
     (let* ((category (or category
 			 org-category
 			 (if buffer-file-name
@@ -4640,6 +4659,24 @@ Any match of REMOVE-RE will be removed from TXT."
 	'extra extra
 	'dotime dotime))))
 
+(defun org-agenda-add-local-tags (txt tags)
+  "Remove tags string from TXT, and add non-inherited list of tags.
+Inherited tags in TAGS are ignored."
+  (if (string-match (org-re "\\([ \t]+\\)\\(:[[:alnum:]_@:]+:\\)[ \t]*$") txt)
+      (setq txt (substring txt 0 (match-beginning 0))))
+  (when tags
+    ;; drop inherited tags
+    (let ((mytags (apply 'append (mapcar
+                                  (lambda (x)
+                                    (if (get-text-property 0 'inherited x)
+                                        nil
+                                      (list x)))
+                                  tags))))
+      ;; continue with remainder
+      (when (> (length mytags) 0)
+        (setq txt (concat txt " :" (mapconcat (lambda (x) x) mytags ":") ":" )))))
+  txt)
+
 (defun org-agenda-add-inherited-tags (txt tags)
   "Remove tags string from TXT, and add complete list of tags.
 The new list includes inherited tags.  If any inherited tags are present,

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