emacs: Improve the display of truncated authors.

Incremental search does not match strings that span a
visible/invisible boundary. This results in failure to correctly
isearch for authors in `notmuch-search' mode if the name of the author
is split between the visible and invisible components of the authors
string. To avoid this, attempt to truncate the visible component of
the authors string on a boundary between authors, such that the
entirety of an author's name is either visible or invisible.

emacs/notmuch.el

@@ -629,49 +629,87 @@ foreground and blue background."
 (defun notmuch-search-isearch-authors-show (overlay)
   (remove-from-invisibility-spec (cons (overlay-get overlay 'invisible) t)))
 
-(defun notmuch-search-insert-authors (format-string authors)
-  (let* ((propertized-authors
-	  ;; Need to save the match data to avoid interfering with
-	  ;; `notmuch-search-process-filter'.
-	  (save-match-data
-	    ;; Authors that don't match the search query are shown in a
-	    ;; different font.
-	    (if (string-match "\\(.*\\)|\\(..*\\)" authors)
+(defun notmuch-search-author-propertize (authors)
+  "Split `authors' into matching and non-matching authors and
+propertize appropriately. If no boundary between authors and
+non-authors is found, assume that all of the authors match."
+  (if (string-match "\\(.*\\)|\\(.*\\)" authors)
       (concat (propertize (concat (match-string 1 authors) ",")
 			  'face 'notmuch-search-matching-authors)
 	      (propertize (match-string 2 authors)
 			  'face 'notmuch-search-non-matching-authors))
-	      (propertize authors 'face 'notmuch-search-matching-authors))))
+    (propertize authors 'face 'notmuch-search-matching-authors)))
 
+(defun notmuch-search-insert-authors (format-string authors)
+  ;; Save the match data to avoid interfering with
+  ;; `notmuch-search-process-filter'.
+  (save-match-data
+    (let* ((formatted-authors (format format-string authors))
 	   (formatted-sample (format format-string ""))
-	 (formatted-authors (format format-string propertized-authors))
-	 visible-string invisible-string)
+	   (visible-string formatted-authors)
+	   (invisible-string "")
+	   (padding ""))
 
-    ;; Determine the part of the authors that will be visible by
-    ;; default.
+      ;; Truncate the author string to fit the specification.
       (if (> (length formatted-authors)
 	     (length formatted-sample))
-	;; 4 is `(length "... ")'.
-	(let ((visible-length (- (length formatted-sample) 4)))
-	  (setq visible-string (substring propertized-authors 0 visible-length)
-		invisible-string (substring propertized-authors visible-length)))
-      (setq visible-string formatted-authors
-	    invisible-string nil))
+	  (let ((visible-length (- (length formatted-sample)
+				   (length "... "))))
+	    ;; Truncate the visible string according to the width of
+	    ;; the display string.
+	    (setq visible-string (substring formatted-authors 0 visible-length)
+		  invisible-string (substring formatted-authors visible-length))
+	    ;; If possible, truncate the visible string at a natural
+	    ;; break (comma or pipe), as incremental search doesn't
+	    ;; match across the visible/invisible border.
+	    (when (string-match "\\(.*\\)\\([,|] \\)\\([^,|]*\\)" visible-string)
+	      ;; Second clause is destructive on `visible-string', so
+	      ;; order is important.
+	      (setq invisible-string (concat (match-string 3 visible-string)
+					     invisible-string)
+		    visible-string (concat (match-string 1 visible-string)
+					   (match-string 2 visible-string))))
+	    ;; `visible-string' may be shorter than the space allowed
+	    ;; by `format-string'. If so we must insert some padding
+	    ;; after `invisible-string'.
+	    (setq padding (make-string (- (length formatted-sample)
+					  (length visible-string)
+					  (length "..."))
+				       ? ))))
 
-    ;; Insert both the visible and invisible author strings.
+      ;; Use different faces to show matching and non-matching authors.
+      (if (string-match "\\(.*\\)|\\(.*\\)" visible-string)
+	  ;; The visible string contains both matching and
+	  ;; non-matching authors.
+	  (setq visible-string (notmuch-search-author-propertize visible-string)
+		;; The invisible string must contain only non-matching
+		;; authors, as the visible-string contains both.
+		invisible-string (propertize invisible-string
+					     'face 'notmuch-search-non-matching-authors))
+	;; The visible string contains only matching authors.
+	(setq visible-string (propertize visible-string
+					 'face 'notmuch-search-matching-authors)
+	      ;; The invisible string may contain both matching and
+	      ;; non-matching authors.
+	      invisible-string (notmuch-search-author-propertize invisible-string)))
+
+      ;; If there is any invisible text, add it as a tooltip to the
+      ;; visible text.
+      (when (not (string= invisible-string ""))
+	(setq visible-string (propertize visible-string 'help-echo (concat "..." invisible-string))))
+
+      ;; Insert the visible and, if present, invisible author strings.
       (insert visible-string)
-    (when invisible-string
+      (when (not (string= invisible-string ""))
 	(let ((start (point))
 	      (invis-spec (make-symbol "notmuch-search-authors"))
 	      overlay)
 	  (insert invisible-string)
-	;; Using a cons-cell here causes an ellipsis to be inserted
-	;; instead of the invisible text.
 	  (add-to-invisibility-spec (cons invis-spec t))
 	  (setq overlay (make-overlay start (point)))
 	  (overlay-put overlay 'invisible invis-spec)
-	(overlay-put overlay 'isearch-open-invisible #'notmuch-search-isearch-authors-show)
-	(insert " ")))))
+	  (overlay-put overlay 'isearch-open-invisible #'notmuch-search-isearch-authors-show)))
+      (insert padding))))
 
 (defun notmuch-search-insert-field (field date count authors subject tags)
   (cond