From 8d09cb21f8ad4c3d3197dadfcc38fe925da558d0 Mon Sep 17 00:00:00 2001
From: Juri Linkov <juri@linkov.net>
Date: Mon, 8 Jul 2019 01:35:35 +0300
Subject: Handle scroll-error-top-bottom in follow.el and view.el (bug#21893)

* lisp/follow.el (follow-scroll-up-arg, follow-scroll-up-window):
Use scroll-up-command instead of scroll-up.
(follow-scroll-down-arg, follow-scroll-down-window):
Use scroll-down-command instead of scroll-down.
(follow-scroll-up, follow-scroll-down): Handle scroll-error-top-bottom.

* lisp/view.el (view-scroll-lines): Use scroll-down-command
instead of scroll-down and scroll-up-command instead of scroll-up.
(view-really-at-end): Handle scroll-error-top-bottom.
---
 lisp/follow.el | 22 ++++++++++++++--------
 lisp/view.el   |  7 ++++---
 2 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/lisp/follow.el b/lisp/follow.el
index acc2b26c550..faac87986bb 100644
--- a/lisp/follow.el
+++ b/lisp/follow.el
@@ -557,7 +557,7 @@ This is an internal function for `follow-scroll-up' and
   (let ((opoint (point))  (owin (selected-window)))
     (while
         ;; If we are too near EOB, try scrolling the previous window.
-        (condition-case nil (progn (scroll-up arg) nil)
+        (condition-case nil (progn (scroll-up-command arg) nil)
           (end-of-buffer
            (condition-case nil (progn (follow-previous-window) t)
              (error
@@ -576,7 +576,7 @@ If ARG is nil, scroll the size of the current window.
 This is an internal function for `follow-scroll-down' and
 `follow-scroll-down-window'."
   (let ((opoint (point)))
-    (scroll-down arg)
+    (scroll-down-command arg)
     (unless (and scroll-preserve-screen-position
                  (get this-command 'scroll-command))
       (goto-char opoint))
@@ -596,7 +596,7 @@ Negative ARG means scroll downward.
 Works like `scroll-up' when not in Follow mode."
   (interactive "P")
   (cond ((not follow-mode)
-	 (scroll-up arg))
+	 (scroll-up-command arg))
 	((eq arg '-)
 	 (follow-scroll-down-window))
 	(t (follow-scroll-up-arg arg))))
@@ -616,7 +616,7 @@ Negative ARG means scroll upward.
 Works like `scroll-down' when not in Follow mode."
   (interactive "P")
   (cond ((not follow-mode)
-	 (scroll-down arg))
+	 (scroll-down-command arg))
 	((eq arg '-)
 	 (follow-scroll-up-window))
 	(t (follow-scroll-down-arg arg))))
@@ -635,13 +635,16 @@ Negative ARG means scroll downward.
 Works like `scroll-up' when not in Follow mode."
   (interactive "P")
   (cond ((not follow-mode)
-	 (scroll-up arg))
+	 (scroll-up-command arg))
 	(arg (follow-scroll-up-arg arg))
         (t
 	 (let* ((windows (follow-all-followers))
 		(end (window-end (car (reverse windows)))))
 	   (if (eq end (point-max))
-	       (signal 'end-of-buffer nil)
+	       (if (or (null scroll-error-top-bottom)
+		       (eobp))
+		   (signal 'end-of-buffer nil)
+		 (goto-char (point-max)))
 	     (select-window (car windows))
 	     ;; `window-end' might return nil.
 	     (if end
@@ -663,14 +666,17 @@ Negative ARG means scroll upward.
 Works like `scroll-down' when not in Follow mode."
   (interactive "P")
   (cond ((not follow-mode)
-	 (scroll-down arg))
+	 (scroll-down-command arg))
 	(arg (follow-scroll-down-arg arg))
         (t
 	 (let* ((windows (follow-all-followers))
 		(win (car (reverse windows)))
 		(start (window-start (car windows))))
 	   (if (eq start (point-min))
-	       (signal 'beginning-of-buffer nil)
+	       (if (or (null scroll-error-top-bottom)
+		       (bobp))
+		   (signal 'beginning-of-buffer nil)
+		 (goto-char (point-min)))
 	     (select-window win)
 	     (goto-char start)
 	     (vertical-motion (- (- (window-height win)
diff --git a/lisp/view.el b/lisp/view.el
index a765be02c1e..e4489b391a9 100644
--- a/lisp/view.el
+++ b/lisp/view.el
@@ -743,18 +743,19 @@ invocations return to earlier marks."
     (setq backward (not backward) lines (- lines)))
   (when (and maxdefault lines (> lines (view-window-size)))
     (setq lines nil))
-  (cond (backward (scroll-down lines))
+  (cond (backward (scroll-down-command lines))
 	((view-really-at-end)
 	 (if view-scroll-auto-exit
 	     (View-quit)
 	   (ding)
 	   (view-end-message)))
-	(t (scroll-up lines)
+	(t (scroll-up-command lines)
 	   (if (view-really-at-end) (view-end-message)))))
 
 (defun view-really-at-end ()
   ;; Return true if buffer end visible.  Maybe revert buffer and test.
-  (and (pos-visible-in-window-p (point-max))
+  (and (or (null scroll-error-top-bottom) (eobp))
+       (pos-visible-in-window-p (point-max))
        (let ((buf (current-buffer))
 	     (bufname (buffer-name))
 	     (file (buffer-file-name)))
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