bug#17453: Isearch doesn't work properly with Follow Mode.

[Juri Linkov]

> So how about us just moving all these checks to where they really
> belong, in isearch-lazy-highlight-update?  I've a feeling that if we do
> this, then your function follow--search-function becomes unneeded.
>
> Juri?

Right, without (sit-for 0) it's possible to switch focus to adjacent windows
with just adding 2 lines to follow.el, i.e. I get the desired behavior with:

diff --git a/lisp/follow.el b/lisp/follow.el
index 938c59e..0433854 100644
--- a/lisp/follow.el
+++ b/lisp/follow.el
@@ -420,6 +420,7 @@ (define-minor-mode follow-mode
   (if follow-mode
       (progn
        (add-hook 'compilation-filter-hook 'follow-align-compilation-windows t 
t)
+       (add-hook 'isearch-update-post-hook 'follow-align-compilation-windows t 
t)
        (add-hook 'post-command-hook 'follow-post-command-hook t)
        (add-hook 'window-size-change-functions 'follow-window-size-change t))
     ;; Remove globally-installed hook functions only if there is no
@@ -432,6 +433,7 @@ (define-minor-mode follow-mode
       (unless following
        (remove-hook 'post-command-hook 'follow-post-command-hook)
        (remove-hook 'window-size-change-functions 'follow-window-size-change)))
+    (remove-hook 'isearch-update-post-hook 'follow-align-compilation-windows t)
     (remove-hook 'compilation-filter-hook 'follow-align-compilation-windows 
t)))
 
 (defun follow-find-file-hook ()
diff --git a/lisp/isearch.el b/lisp/isearch.el
index b762884..8edf8b0 100644
--- a/lisp/isearch.el
+++ b/lisp/isearch.el
@@ -3018,7 +3018,7 @@ (defun isearch-lazy-highlight-new-loop (&optional beg end)
 search string to change or the window to scroll).  It is also used
 by other Emacs features."
   (when (and (null executing-kbd-macro)
-             (sit-for 0)         ;make sure (window-start) is credible
+             ; (sit-for 0)         ;make sure (window-start) is credible
              (or (not (equal isearch-string
                              isearch-lazy-highlight-last-string))
                  (not (eq (selected-window)


So what remains to do is to fix this bug, but I don't understand the logic
you proposed: how checks could be moved to isearch-lazy-highlight-update
if isearch-lazy-highlight-update is scheduled by a timer conditionally
depending on these checks?