bug#12796: Optimize `ido-completing-read' for larger lists with flex matching enabled

[Dmitry Gutov <dgutov@yandex.ru>]

On 06.11.2012 15:03, Kim Storm wrote:
> On 2012-11-06 02:45, Stefan Monnier wrote:
>> [ Hi Kim, can you give me your opinion on this?  ]
>>
>>> To try it, I just wrapped in it the "busy" part of `ido-set-matches-1' -
>>> and indeed, no more waiting a several seconds after button
>>> mashing. It's a bit buggy so far, but that's to be expected.
>> To eliminate the buggy behavior, it should probably be put elsewhere,
>> maybe directly in ido-exhibit (the post-command-hook).
> Sounds right, but I a bit worried that some of the state information
> may get corrupted if arbitrarily interrupted by user input.
>
> If someone proposes a patch, I'll look at it.

How does this look to you?

I added a new var because ido-rescan is unconditionally set to nil in 
many places.

By the way, is there a place where ido-rotate is set to anything but 
nil? Does this variable actually do anything?

=== modified file 'lisp/ido.el'
--- lisp/ido.el	2012-10-05 07:38:05 +0000
+++ lisp/ido.el	2012-11-07 05:34:53 +0000
@@ -1020,6 +1020,9 @@
  (defvar ido-rotate nil
    "Non-nil means we are rotating list of matches.")

+(defvar ido-interrupted nil
+  "Non-nil means calculation of matches was interrupted by keyboard 
input.")
+
  (defvar ido-text nil
    "Stores the users string as it is typed in.")

@@ -3778,9 +3781,14 @@

  (defun ido-set-matches ()
    ;; Set `ido-matches' to the list of items matching prompt
-  (when ido-rescan
-    (setq ido-matches (ido-set-matches-1 (reverse ido-cur-list) (not 
ido-rotate))
-	  ido-rotate nil)))
+  (when (or ido-rescan ido-interrupted)
+    (setq ido-interrupted t)
+    (while-no-input
+      (setq ido-matches (ido-set-matches-1 (reverse ido-cur-list)
+                                           (not ido-rotate))
+            ido-interrupted nil
+            ido-rotate nil))
+    (when ido-interrupted (setq ido-matches nil))))

  (defun ido-ignore-item-p (name re-list &optional ignore-ext)
    ;; Return t if the buffer or file NAME should be ignored.
@@ -4513,11 +4521,12 @@
  	      (exit-minibuffer)))

  	;; Insert the match-status information:
-	(ido-set-common-completion)
-	(let ((inf (ido-completions contents)))
-	  (setq ido-show-confirm-message nil)
-	  (ido-trace "inf" inf)
-	  (insert inf))
+        (unless ido-interrupted
+          (ido-set-common-completion)
+          (let ((inf (ido-completions contents)))
+            (setq ido-show-confirm-message nil)
+            (ido-trace "inf" inf)
+            (insert inf)))
  	))))

  (defun ido-completions (name)