bug#18618: 25.0.50; `window-end win t` produces erroenous result with `window-scroll-functions` hook.

[Keith David Bershatsky]

Steps to reproduce the issue.

1.  Create a function that reports (e.g., a message) the value of `(window-end 
win t)` and attach that function to the `window-scroll-functions` hook.

2.  Open a long file in either fundamental-mode or text-mode.

3.  M-x end-of-buffer

4.  M-x beginning-of-buffer

The result of step 4 reports an erroneous window-end value that is at the very 
end of the buffer, instead of the correct window-end (i.e., which is much 
closer to the beginning of the buffer).

This makes it impossible to correctly draw overlays between window-start and 
window-end, because Emacs thinks the entire buffer should be used following an 
interactive use of `beginning-of-buffer`.

Please feel free to use my test-mode, which is a minor mode for testing 
window-start and window-end.

Thanks,

Keith

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;; test-mode

(defvar test-old-window-start nil
"This local variable is set within the `post-command-hook`; and,
is also used by the `window-scroll-functions` hook.")
(make-variable-buffer-local 'test-old-window-start)

(defvar test-old-window-end nil
"This local variable is set within the `post-command-hook`; and,
is also used by the `window-scroll-functions` hook.")
(make-variable-buffer-local 'test-old-window-end)

(defvar test-old-window-end-forced nil
"This local variable is set within the `post-command-hook`; and,
is also used by the `window-scroll-functions` hook.")
(make-variable-buffer-local 'test-old-window-end-forced)

(defvar test-new-window-start nil
"This local variable is set within the `window-scroll-functions`.")
(make-variable-buffer-local 'test-new-window-start)

(defvar test-new-window-end nil
"This local variable is set within the `window-scroll-functions`.")
(make-variable-buffer-local 'test-new-window-end)

(defun test-post-command-hook ()
"NOT good for things like: `beginning-of-buffer`; `end-of-buffer`; `yank`; etc.
NOTE:  When using `this-command` in conjunction with the `post-command-hook`,
the `window-scroll-functions` hook would need to use `last-command`."
  (when
      (and
        (not (minibufferp))
        (window-live-p (get-buffer-window (current-buffer))))
    (setq test-old-window-start (window-start))
    (setq test-old-window-end (window-end))
    (setq test-old-window-end-forced (window-end nil t))
    ;; DEBUGGING TEST
    ;;  (message "pt: %s | ows: %s | owe: %s | owe-f: %s"
    ;;    (point)
    ;;    test-old-window-start
    ;;    test-old-window-end
    ;;    test-old-window-end-forced)
    (when
        (or
          (and
            (not (< (point) test-old-window-start))
            (pos-visible-in-window-p (point)
              (get-buffer-window (current-buffer) (selected-frame)))
            (not (> (point) test-old-window-end))
            (not (> (point) test-old-window-end-forced)))
          ;; special situation when deleting region greater than size of window.
          (and
            (region-active-p)
            (< test-old-window-end 0))
          ;; special situation when deleting region greater than size of window.
          (and
            (region-active-p)
            (> (point) test-old-window-start)
            (> (point) test-old-window-end)
            (< (point) test-old-window-end-forced)) )
      (test-mode-demonstration
        test-old-window-start
        test-old-window-end
        test-old-window-end-forced
        nil
        nil))))

(defun test-window-scroll-functions (win _start)
"Good for things like: `beginning-of-buffer`; `end-of-buffer`; `yank`; etc.
NOTE:  When using `this-command` in conjunction with the `post-command-hook`,
the `window-scroll-functions` hook would need to use `last-command`."
  (when
      (and
        test-old-window-start
        test-old-window-end
        test-old-window-end-forced
        (not (minibufferp))
        (window-live-p (get-buffer-window (current-buffer))))
    ;; DEBUGGING TEST
    ;; (message "nws: %s | nwe-f: %s" _start (window-end nil t))
    (when
        (or
          (not (= _start test-old-window-start))
          (not (pos-visible-in-window-p (point)
            (get-buffer-window (current-buffer) (selected-frame))))
          (< (point) test-old-window-start)
          (> (point) test-old-window-end)
          (> (point) test-old-window-end-forced))
      (setq test-new-window-start _start)
      (setq test-new-window-end (window-end win t))
      ;; FIX-ME -- special circumstance when jumping paragraph down.
      ;; (when (> (point) test-new-window-end)
      ;; (setq test-new-window-end . . .
      (test-mode-demonstration
        nil
        nil
        nil
        test-new-window-start
        test-new-window-end)
      (setq test-old-window-start nil)
      (setq test-old-window-end nil)
      (setq test-old-window-end-forced nil))))

(defun test-mode-demonstration
  (&optional
    test-old-window-start
    test-old-window-end
    test-old-window-end-forced
    test-new-window-start
    test-new-window-end)
"This is a test-mode demonstration function."
  (let* (
      (window-start
        (cond
          (test-old-window-start
            test-old-window-start)
          (test-new-window-start
            test-new-window-start)
          (t (window-start))))
      (window-end
        (cond
          ((and
              test-old-window-end
              test-old-window-end-forced
              (= test-old-window-end test-old-window-end-forced))
            test-old-window-end)
          ((and
              test-old-window-end
              test-old-window-end-forced
              (> test-old-window-end-forced test-old-window-end))
            test-old-window-end-forced)
          (test-new-window-end
            test-new-window-end)
          (t (window-end (selected-window) t)))) )
    (cond
      ((and
          test-old-window-start
          test-old-window-end
          test-old-window-end-forced)
        (message (concat
        "P.C.H. -- `point`: %s | "
        "`test-old-window-start`: %s | "
        "`test-old-window-end`: %s | "
        "`test-old-window-end-forced`: %s")
          (point)
          test-old-window-start
          test-old-window-end
          test-old-window-end-forced))
      ((and
          test-new-window-start
          test-new-window-end)
        (message (concat
          "W.S.F. -- `point`: %s | "
          "`test-new-window-start`: %s | "
          "`test-new-window-end`: %s")
            (point)
            test-new-window-start
            test-new-window-end))) ))

(define-minor-mode test-mode
"A minor-mode for testing `window-start` / `window-end` BEFORE visual 
redisplay."
  :init-value nil
  :lighter " TEST"
  :keymap nil
  :global nil
  :group nil
  (cond
    (test-mode
      (condition-case error
        (progn
          (setq scroll-conservatively 101)
          (setq max-mini-window-height 2)
          (add-hook 'post-command-hook 'test-post-command-hook nil t)
          (add-hook 'window-scroll-functions 'test-window-scroll-functions nil 
t)
          (when (called-interactively-p 'any)
            (message "Turned ON `test-mode`.")))
        (error
         (test-mode 0)
         (signal (car error) (cdr error)))))
    ((not test-mode)
      (setq max-mini-window-height 0.25)
      (remove-hook 'post-command-hook 'test-post-command-hook t)
      (remove-hook 'window-scroll-functions 'test-window-scroll-functions t)
      (when (called-interactively-p 'any)
        (message "Turned OFF `test-mode`.") ))))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;


In GNU Emacs 25.0.50.1 (x86_64-apple-darwin10.8.0, NS appkit-1038.36 Version 
10.6.8 (Build 10K549))
 of 2014-10-01 on MP.local
Repository revision: 117996 dmantipov@yandex.ru-20141001132108-zdsxru2390mqyjlu
Windowing system distributor `Apple', version 10.3.1038
Configured using:
 `configure --with-ns'

Configured features:
ACL LIBXML2 ZLIB

Important settings:
  locale-coding-system: utf-8-unix

Major mode: Text

Minor modes in effect:
  sd-mode: t
  test-mode: t
  sb-mode: t
  tb-mode: t
  shell-dirtrack-mode: t
  cm-mode: t
  bc-mode: t
  as-mode: t
  ds-mode: t
  ml-mode: t

Recent input:

Recent messages:
Mark set
W.S.F. -- `point`: 1 | `test-new-window-start`: 1 | `test-new-window-end`: 
339823
Turned ON `test-mode`.
P.C.H. -- `point`: 1191 | `test-old-window-start`: 1 | `test-old-window-end`: 
5438 | `test-old-window-end-forced`: 5438
W.S.F. -- `point`: 339823 | `test-new-window-start`: 339179 | 
`test-new-window-end`: 339823
Mark set
W.S.F. -- `point`: 1 | `test-new-window-start`: 1 | `test-new-window-end`: 
339823
W.S.F. -- `point`: 339823 | `test-new-window-start`: 339179 | 
`test-new-window-end`: 339823
Mark set
W.S.F. -- `point`: 1 | `test-new-window-start`: 1 | `test-new-window-end`: 
339823

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