[PATCH 3/5] emacs: show: mark tags changed since buffer loaded

[Mark Walters]

This shows any tags changed in the show buffer since it was loaded or
refreshed. By default a removed tag is displayed with strike-through
in red (if strike-through is not available, eg on a terminal, inverse
video is used instead) and an added tag is displayed underlined in
green.

One nice feature is that this makes it clear when a message was unread
when you first loaded the buffer (previously the unread tag could be
removed before a user realised that it had been unread).

The code adds into the existing tag formatting code. The user can
specify exactly how a tag should be displayed normally, when deleted,
or when added. For convenience an entry for the entry string in the
notmuch-tag-formats (and the corresponding notmuch-tag-deleted-formats
notmuch-tag-added-formats) is applied to all tags which do not have an
explicit match.

This means that a user can tell notmuch not to show deleted tags at
all by setting notmuch-tag-deleted-formats to
'(("" nil))
or not to show any deleted tags except "unread" by setting it to
'(("" nil)
  ("unread" (propertize tag 'face '(strike-through "red"))))

All the variables are customizable; however, more complicated cases
like changing the face depending on the type of display will require
custom lisp.

Currently this overrides notmuch-tag-deleted-formats for the tests
setting it to '(("" nil)) so that they get removed from the display
and, thus, all tests still pass.
---
 emacs/notmuch-show.el |   22 ++++++++--
 emacs/notmuch-tag.el  |  105 +++++++++++++++++++++++++++++++++++--------------
 test/test-lib.el      |    4 ++
 3 files changed, 96 insertions(+), 35 deletions(-)

diff --git a/emacs/notmuch-show.el b/emacs/notmuch-show.el
index 1ac80ca..30e84b1 100644
--- a/emacs/notmuch-show.el
+++ b/emacs/notmuch-show.el
@@ -341,11 +341,21 @@ operation on the contents of the current buffer."
   "Update the displayed tags of the current message."
   (save-excursion
     (goto-char (notmuch-show-message-top))
-    (if (re-search-forward "(\\([^()]*\\))$" (line-end-position) t)
-	(let ((inhibit-read-only t))
-	  (replace-match (concat "("
-				 (notmuch-tag-format-tags tags)
-				 ")"))))))
+    (let* ((orig-tags (notmuch-show-get-prop :orig-tags))
+	   (all-tags (sort (delete-dups (append tags orig-tags)) #'string<))
+	   (display-tags (mapcar (lambda (tag) (cond ((and (member tag tags) (member tag orig-tags))
+						      tag)
+						     ((not (member tag tags))
+						      (cons tag 'deleted))
+						     ((not (member tag orig-tags))
+						      (cons tag 'added))))
+				 all-tags)))
+
+      (if (re-search-forward "(\\([^()]*\\))$" (line-end-position) t)
+	  (let ((inhibit-read-only t))
+	    (replace-match (concat "("
+				   (notmuch-tag-format-tags display-tags)
+				   ")")))))))
 
 (defun notmuch-clean-address (address)
   "Try to clean a single email ADDRESS for display. Return a cons
@@ -1167,6 +1177,8 @@ function is used."
 
       (jit-lock-register #'notmuch-show-buttonise-links)
 
+      (notmuch-show-mapc (lambda () (notmuch-show-set-prop :orig-tags (notmuch-show-get-tags))))
+
       ;; Set the header line to the subject of the first message.
       (setq header-line-format (notmuch-sanitize (notmuch-show-strip-re (notmuch-show-get-subject))))
 
diff --git a/emacs/notmuch-tag.el b/emacs/notmuch-tag.el
index b60f46c..81ce287 100644
--- a/emacs/notmuch-tag.el
+++ b/emacs/notmuch-tag.el
@@ -28,34 +28,8 @@
 (require 'crm)
 (require 'notmuch-lib)
 
-(defcustom notmuch-tag-formats
-  '(("unread" (propertize tag 'face '(:foreground "red")))
-    ("flagged" (propertize tag 'face '(:foreground "blue"))
-     (notmuch-tag-format-image-data tag (notmuch-tag-star-icon))))
-  "Custom formats for individual tags.
-
-This gives a list that maps from tag names to lists of formatting
-expressions.  The car of each element gives a tag name and the
-cdr gives a list of Elisp expressions that modify the tag.  If
-the list is empty, the tag will simply be hidden.  Otherwise,
-each expression will be evaluated in order: for the first
-expression, the variable `tag' will be bound to the tag name; for
-each later expression, the variable `tag' will be bound to the
-result of the previous expression.  In this way, each expression
-can build on the formatting performed by the previous expression.
-The result of the last expression will displayed in place of the
-tag.
-
-For example, to replace a tag with another string, simply use
-that string as a formatting expression.  To change the foreground
-of a tag to red, use the expression
-  (propertize tag 'face '(:foreground \"red\"))
-
-See also `notmuch-tag-format-image', which can help replace tags
-with images."
-
-  :group 'notmuch-search
-  :group 'notmuch-show
+(define-widget 'notmuch-tag-format-type 'lazy
+  "Customize widget for notmuch-tag-format and friends"
   :type '(alist :key-type (string :tag "Tag")
 		:extra-offset -3
 		:value-type
@@ -82,6 +56,61 @@ with images."
 					  (string :tag "Custom")))
 			    (sexp :tag "Custom")))))
 
+(defcustom notmuch-tag-formats
+  '(("unread" (propertize tag 'face '(:foreground "red")))
+    ("flagged" (propertize tag 'face '(:foreground "blue"))
+     (notmuch-tag-format-image-data tag (notmuch-tag-star-icon))))
+  "Custom formats for individual tags.
+
+This gives a list that maps from tag names to lists of formatting
+expressions.  The car of each element gives a tag name and the
+cdr gives a list of Elisp expressions that modify the tag. If the
+car is an empty string it matches all tags that do not have an
+explicit match. If the list is empty, the tag will simply be
+hidden.  Otherwise, each expression will be evaluated in order:
+for the first expression, the variable `tag' will be bound to the
+tag name; for each later expression, the variable `tag' will be
+bound to the result of the previous expression.  In this way,
+each expression can build on the formatting performed by the
+previous expression.  The result of the last expression will
+displayed in place of the tag.
+
+For example, to replace a tag with another string, simply use
+that string as a formatting expression.  To change the foreground
+of a tag to red, use the expression
+  (propertize tag 'face '(:foreground \"red\"))
+
+See also `notmuch-tag-format-image', which can help replace tags
+with images."
+  :group 'notmuch-search
+  :group 'notmuch-show
+  :type 'notmuch-tag-format-type)
+
+(defcustom notmuch-tag-deleted-formats
+  '(("" (propertize tag 'face
+		   (if (display-supports-face-attributes-p '(:strike-through "red"))
+		       '(:strike-through "red")
+		     '(:inverse-video t)))))
+  "Custom formats for tags when deleted.
+
+By default this shows deleted tags with strike-through in red,
+unless strike-through is not available (e.g., emacs is running in
+a terminal) in which case it uses inverse video. To hide deleted
+tags completely set this to
+  '((\"\" nil))
+
+See `notmuch-tag-formats' for full documentation."
+  :group 'notmuch-show
+  :type 'notmuch-tag-format-type)
+
+(defcustom notmuch-tag-added-formats
+  '(("" (propertize tag 'face '(:underline "green"))))
+  "Custom formats for tags when added.
+
+See `notmuch-tag-formats' for full documentation."
+  :group 'notmuch-show
+  :type 'notmuch-tag-format-type)
+
 (defun notmuch-tag-format-image-data (tag data)
   "Replace TAG with image DATA, if available.
 
@@ -136,8 +165,24 @@ This can be used with `notmuch-tag-format-image-data'."
 </svg>")
 
 (defun notmuch-tag-format-tag (tag)
-  "Format TAG by looking into `notmuch-tag-formats'."
-  (let ((formats (assoc tag notmuch-tag-formats)))
+  "Format TAG by looking into `notmuch-tag-formats'.
+
+TAG can either be a string for a tag or a cons cell. In the
+latter case the car of the cons cell is the tag string, the cdr
+should be 'deleted or 'added to indicate whether the tag has been
+deleted or added. The format for tag is looked up in
+`notmuch-tag-formats' or `notmuch-tag-deleted-formats' or
+`notmuch-tag-added-formats' as appropriate."
+  (let* ((status (if (consp tag) (cdr tag)))
+	 (tag (if (consp tag) (car tag) tag))
+	 (status-formats (cond
+			  ((eq status 'deleted)
+			   notmuch-tag-deleted-formats)
+			  ((eq status 'added)
+			   notmuch-tag-added-formats)
+			  (t notmuch-tag-formats)))
+	 (formats (or (append (assoc tag status-formats))
+		      (append (assoc "" status-formats)))))
     (cond
      ((null formats)		;; - Tag not in `notmuch-tag-formats',
       tag)			;;   the format is the tag itself.
diff --git a/test/test-lib.el b/test/test-lib.el
index 1c9e224..a1b40b7 100644
--- a/test/test-lib.el
+++ b/test/test-lib.el
@@ -174,3 +174,7 @@ nothing."
     (dolist (form body ret)
       (setq ret (eval form))
       (notmuch-post-command))))
+
+;; hide deleted tags
+(setq notmuch-tag-deleted-formats
+      '(("" nil)))
-- 
1.7.9.1