bug#21092: 25.0.50; Option `lazy-highlight-max-at-a-time' does not work

[Drew Adams <drew.adams@oracle.com>]

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> OK, I think I found the problem.  I have something working,
> but will send it in the form of a patch in a while.
> 
> Essentially, it is the isearch.el code itself that imposes, in
> a few places, not searching past (window-end) or before
> (window-start), regardless of the value of
> `isearch-lazy-highlight-max-at-a-time'.  This is what needs to
> be fixed, to be (point-max) and (point-min) when
> `isearch-lazy-highlight-max-at-a-time' is nil.
> 
> A more thoroughgoing fix would take into account a numeric
> value of `isearch-lazy-highlight-max-at-a-time', but I won't
> bother with that, for now.

Attached is a quick patch that seems to be OK wrt fixing
things for a nil value of `isearch-lazy-highlight-max-at-a-time'.

Please give it a try.  If OK then I will update the doc and
defcustom to make clear that (for now) this works only for
nil and not for a large value.

Feel free to adjust the fix.  Or to extend it to also take a
numeric value into account.  But I will be happy if it is fixed
at least for nil.

[-- Attachment #2: isearch-2015-08-28.patch --]
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diff -uw isearch.el isearch-patched-2015-08-28.el
--- isearch.el	2015-08-28 09:47:45.431252800 -0700
+++ isearch-patched-2015-08-28.el	2015-08-28 09:51:40.683708500 -0700
@@ -3092,13 +3092,13 @@
 				(+ isearch-lazy-highlight-start
 				   ;; Extend bound to match whole string at point
 				   (1- (length isearch-lazy-highlight-last-string)))
-			      (window-end)))
+			      (if lazy-highlight-max-at-a-time (window-end) (point-max))))
 		     (max (or isearch-lazy-highlight-start-limit (point-min))
 			  (if isearch-lazy-highlight-wrapped
 			      (- isearch-lazy-highlight-end
 				 ;; Extend bound to match whole string at point
 				 (1- (length isearch-lazy-highlight-last-string)))
-			    (window-start))))))
+			    (if lazy-highlight-max-at-a-time (window-start) (point-max)))))))
 	;; Use a loop like in `isearch-search'.
 	(while retry
 	  (setq success (isearch-search-string
@@ -3142,12 +3142,12 @@
 			  (if isearch-lazy-highlight-forward
 			      (if (= mb (if isearch-lazy-highlight-wrapped
 					    isearch-lazy-highlight-start
-					  (window-end)))
+					  (if max (window-end) (point-max))))
 				  (setq found nil)
 				(forward-char 1))
 			    (if (= mb (if isearch-lazy-highlight-wrapped
 					  isearch-lazy-highlight-end
-					(window-start)))
+					(if max (window-start) (point-min))))
 				(setq found nil)
 			      (forward-char -1)))