bug#12638: 24.2.50; FR: Some suggestions for icomplete-mode

[Jambunathan K]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> I'd like to go for the () annotation, but I'm pretty swamped, so
> progress is slow.

=== modified file 'lisp/ChangeLog'
--- lisp/ChangeLog      2013-02-13 13:40:00 +0000
+++ lisp/ChangeLog      2013-02-13 13:52:00 +0000
@@ -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  Stefan Monnier  <monnier@iro.umontreal.ca>
 
        * tmm.el: Use lexical-binding and current-active-maps.

=== modified file 'lisp/icomplete.el'
--- lisp/icomplete.el   2013-02-08 07:53:55 +0000
+++ lisp/icomplete.el   2013-02-13 13:31:04 +0000
@@ -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]"))))))

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