2 files changed, 55 insertions, 15 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index f104a4dfe3a..4976d5b9410 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,10 @@
+2013-02-13  Jambunathan K  <kjambunathan@gmail.com>
+
+        * icomplete.el (icomplete-hide-common-prefix):  New user option.
+        (icomplete-first-match): New face.
+        (icomplete-completions): Correct handling of "complete but not
+        unique" (Bug#12638).
+
 2013-02-13  YE Qianchuan  <stool.ye@gmail.com>  (tiny change)
 
         * descr-text.el (describe-char): Display the script (bug#13698).
diff --git a/lisp/icomplete.el b/lisp/icomplete.el
index 8e4dd69e199..1f9b4a3afe6 100644
--- a/lisp/icomplete.el
+++ b/lisp/icomplete.el
@@ -76,6 +76,18 @@
   :type 'string
   :version "24.4")
 
+(defcustom icomplete-hide-common-prefix t
+  "When non-nil, hide common prefix from completion candidates.
+When nil, show candidates in full."
+  :type 'boolean
+  :version "24.4"
+  :group 'icomplete)
+
+(defface icomplete-first-match  '((t :weight bold))
+  "Face used by icomplete for highlighting first match."
+  :version "24.4"
+  :group 'icomplete)
+
 ;;;_* User Customization variables
 (defcustom icomplete-prospects-height
   ;; 20 is an estimated common size for the prompt + minibuffer content, to
@@ -344,7 +356,8 @@ are exhibited within the square braces.)"
                                 (t (concat "…" (substring most compare))))
                                close-bracket)))
              ;;"-prospects" - more than one candidate
-             (prospects-len (+ (length determ)
+             (prospects-len (+ (string-width
+                                (or determ (concat open-bracket close-bracket)))
                                (string-width icomplete-separator)
                                3 ;; take {…} into account
                                (string-width (buffer-string))))
@@ -355,6 +368,8 @@ are exhibited within the square braces.)"
                     ;; one line, increase the allowable space accordingly.
                     (/ prospects-len (window-width)))
                  (window-width)))
+             (prefix (when icomplete-hide-common-prefix
+                       (try-completion "" comps)))
              (prefix-len
               ;; Find the common prefix among `comps'.
               ;; We can't use the optimization below because its assumptions
@@ -364,37 +379,55 @@ are exhibited within the square braces.)"
               ;;     ;; Common case.
               ;;     (length most)
               ;; Else, use try-completion.
-              (let ((comps-prefix (try-completion "" comps)))
-                (and (stringp comps-prefix)
-                     (length comps-prefix)))) ;;)
-
-             prospects most-is-exact comp limit)
+              (and (stringp prefix) (length prefix))) ;;)
+             prospects comp limit)
         (if (eq most-try t) ;; (or (null (cdr comps))
             (setq prospects nil)
+          (when (member name comps)
+            ;; NAME is complete but not unique.  This scenario poses
+            ;; following UI issues:
+            ;;
+            ;; - When `icomplete-hide-common-prefix' is non-nil, NAME
+            ;;   is stripped empty.  This would make the entry
+            ;;   inconspicuous.
+            ;;
+            ;; - Due to sorting of completions, NAME may not be the
+            ;;   first of the prospects and could be hidden deep in
+            ;;   the displayed string.
+            ;;
+            ;; - Because of `icomplete-prospects-height' , NAME may
+            ;;   not even be displayed to the user.
+            ;;
+            ;; To circumvent all the above problems, provide a visual
+            ;; cue to the user via an "empty string" in the try
+            ;; completion field.
+            (setq determ (concat open-bracket "" close-bracket)))
+          ;; Compute prospects for display.
           (while (and comps (not limit))
             (setq comp
                   (if prefix-len (substring (car comps) prefix-len) (car comps))
                   comps (cdr comps))
-            (cond ((string-equal comp "") (setq most-is-exact t))
-                  ((member comp prospects))
-                  (t (setq prospects-len
+            (setq prospects-len
                            (+ (string-width comp)
                               (string-width icomplete-separator)
                               prospects-len))
                      (if (< prospects-len prospects-max)
                          (push comp prospects)
-                       (setq limit t))))))
+              (setq limit t))))
+        (setq prospects (nreverse prospects))
+        ;; Decorate first of the prospects.
+        (when prospects
+          (let ((first (copy-sequence (pop prospects))))
+            (put-text-property 0 (length first)
+                               'face 'icomplete-first-match first)
+            (push first prospects)))
         ;; Restore the base-size info, since completion-all-sorted-completions
         ;; is cached.
         (if last (setcdr last base-size))
         (if prospects
             (concat determ
                     "{"
-                    (and most-is-exact
-                         (substring icomplete-separator
-                                    (string-match "[^ ]" icomplete-separator)))
-                    (mapconcat 'identity (nreverse prospects)
-                               icomplete-separator)
+                    (mapconcat 'identity prospects icomplete-separator)
                     (and limit (concat icomplete-separator "…"))
                     "}")
           (concat determ " [Matched]"))))))