emacs: Use text properties instead of overlays for tag coloring

Previously, tag-based search result highlighting was done by creating
an overlay over each search result.  However, overlays have annoying
front- and rear-advancement semantics that make it difficult to
manipulate text at their boundaries, which the next patch will do.
They also have performance problems (creating an overlay is linear in
the number of overlays between point and the new overlay, making
highlighting a search buffer quadratic in the number of results).

Text properties have neither problem.  However, text properties make
it more difficult to apply multiple faces since, unlike with overlays,
a given character can only have a single 'face text property.  Hence,
we introduce a utility function that combines faces into any existing
'face text properties.

Using this utility function, it's straightforward to apply all of the
appropriate tag faces in notmuch-search-color-line.

diff --git a/emacs/notmuch-lib.el b/emacs/notmuch-lib.el
index aa25513a3b6500b1f36ab12e16d252f2cce2aca5..30db58ffbff32c2d703c22f3a21427402a08b20d 100644 (file)
--- a/emacs/notmuch-lib.el
+++ b/emacs/notmuch-lib.el
@@ -269,6 +269,21 @@ current buffer, if possible."
   (loop for (key value . rest) on plist by #'cddr
        collect (cons (intern (substring (symbol-name key) 1)) value)))
 
+(defun notmuch-combine-face-text-property (start end face)
+  "Combine FACE into the 'face text property between START and END.
+
+This function combines FACE with any existing faces between START
+and END.  Attributes specified by FACE take precedence over
+existing attributes.  FACE must be a face name (a symbol or
+string), a property list of face attributes, or a list of these."
+
+  (let ((pos start))
+    (while (< pos end)
+      (let ((cur (get-text-property pos 'face))
+           (next (next-single-property-change pos 'face nil end)))
+       (put-text-property pos next 'face (cons face cur))
+       (setq pos next)))))
+
 ;; Compatibility functions for versions of emacs before emacs 23.
 ;;
 ;; Both functions here were copied from emacs 23 with the following copyright:

diff --git a/emacs/notmuch.el b/emacs/notmuch.el
index ef1892732d09f4278547f4f8ed2f5b671908eeda..82c148dfb0930068b2796809c9ff3ce8cb8fa035 100644 (file)
--- a/emacs/notmuch.el
+++ b/emacs/notmuch.el
@@ -633,20 +633,13 @@ foreground and blue background."
 
 (defun notmuch-search-color-line (start end line-tag-list)
   "Colorize lines in `notmuch-show' based on tags."
-  ;; Create the overlay only if the message has tags which match one
-  ;; of those specified in `notmuch-search-line-faces'.
-  (let (overlay)
-    (mapc (lambda (elem)
-           (let ((tag (car elem))
-                 (attributes (cdr elem)))
-             (when (member tag line-tag-list)
-               (when (not overlay)
-                 (setq overlay (make-overlay start end)))
-               ;; Merge the specified properties with any already
-               ;; applied from an earlier match.
-               (overlay-put overlay 'face
-                            (append (overlay-get overlay 'face) attributes)))))
-         notmuch-search-line-faces)))
+  (mapc (lambda (elem)
+         (let ((tag (car elem))
+               (attributes (cdr elem)))
+           (when (member tag line-tag-list)
+             (notmuch-combine-face-text-property start end attributes))))
+       ;; Reverse the list so earlier entries take precedence
+       (reverse notmuch-search-line-faces)))
 
 (defun notmuch-search-author-propertize (authors)
   "Split `authors' into matching and non-matching authors and