First commit to scratch/follow. Make Isearch work with Follow Mode, etc.
doc/lispref/window.texi (Basic Windows): Add paragraph defining "Group of
Windows" and new @defun selected-window-group.
(Window Start and End): Describe new &optional parameter GROUP and
...-group-function for window-start, window-end, set-window-start, and
pos-visible-in-window-p.
(Textual Scrolling) Describe the same for recenter.
doc/lispref/positions.texi (Screen Lines): Describe the same for
move-to-window-line.
src/window.c (Fwindow_start, Fwindow_end, Fset_window_start)
(Fpos_visible_in_window_p, Frecenter, Fmove_to_window_line): To each, add ar
new optional parameter "group". At the beginning of each, check whether the
corresponding ...-group-function is set to a function, and if so execute this
function in place of the normal processing.
(syms_of_window): Define symbols for the six new variables below.
(window-start-group-function, window-end-group-function)
(set-window-start-group-function, recenter-group-function)
(pos-visible-in-window-p-group-function, move-to-window-line-group-function):
New permanent local buffer local variables.
src/keyboard.c (Fposn_at_point): Add extra parameter in call to
Fpos_visible_in_window_p.
lisp/window.el (selected-window-group-function): New permanent local buffer
local variable.
(selected-window-group): New function.
lisp/follow.el (follow-mode): Set the ...-group-function variables at mode
enable, kill them at mode disable. Add/remove follow-after-change to/from
after-change-functions.
(follow-start-end-invalid): New variable.
(follow-redisplay): Manipulate follow-start-end-invalid.
(follow-after-change, follow-window-start, follow-window-end)
(follow-set-window-start, follow-pos-visible-in-window-p)
(follow-move-to-window-line, follow-sit-for): New functions.
lisp/isearch.el (isearch-call-message): New macro.
(isearch-update, with-isearch-suspended, isearch-del-char)
(isearch-search-and-update, isearch-ring-adjust): Invoke above new macro.
(with-isearch-suspended): Rearrange code such that isearch-call-message is
invoked before point is moved.
(isearch-message): Add comment about where point must be at function call.
(isearch-search): Remove call to isearch-message.
(isearch-lazy-highlight-window-group): New variable.
(isearch-lazy-highlight-new-loop): Unconditionally start idle timer. Move
the battery of tests to ...
(isearch-lazy-highlight-maybe-new-loop): New function, started by idle timer.
Note: (sit-for 0) is still called.
(isearch-lazy-highlight-update): Check membership of
isearch-lazy-highlight-window-group. Don't set the `window' overlay
property.
(isearch-update, isearch-done, isearch-string-out-of-window)
(isearch-back-into-window, isearch-lazy-highlight-maybe-new-loop)
(isearch-lazy-highlight-search, isearch-lazy-highlight-update)
(isearch-lazy-highlight-update): Call the six amended primitives (see
src/window.c above) with the new `group' argument set to t, to cooperate
with Follow Mode.