From 0f6bbc3da36a77fbdd07e801fd1755702b157a6e Mon Sep 17 00:00:00 2001
From: Eli Zaretskii <eliz@gnu.org>
Date: Sun, 27 Jul 2014 21:05:37 +0300
Subject: [PATCH] Support horizontal scrolling of bidirectional text.

 lisp/scroll-bar.el (scroll-bar-toolkit-horizontal-scroll): Add
 rudimentary support for bidirectional text.
---
 lisp/ChangeLog     |  5 +++++
 lisp/scroll-bar.el | 30 +++++++++++++++++++-----------
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 3f97396ca02..dd87a610057 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2014-07-27  Eli Zaretskii  <eliz@gnu.org>
+
+	* scroll-bar.el (scroll-bar-toolkit-horizontal-scroll): Add
+	rudimentary support for bidirectional text.
+
 2014-07-27  Martin Rudalics  <rudalics@gmx.at>
 
 	* frame.el (frame-notice-user-settings): Rewrite using
diff --git a/lisp/scroll-bar.el b/lisp/scroll-bar.el
index 09f30d5d3f0..739670cb1c9 100644
--- a/lisp/scroll-bar.el
+++ b/lisp/scroll-bar.el
@@ -451,6 +451,9 @@ EVENT should be a scroll bar click."
   (let* ((end-position (event-end event))
 	 (window (nth 0 end-position))
 	 (part (nth 4 end-position))
+	 (bidi-factor (if (eq (current-bidi-paragraph-direction) 'left-to-right)
+			  1
+			-1))
 	 before-scroll)
     (cond
      ((eq part 'end-scroll))
@@ -462,27 +465,32 @@ EVENT should be a scroll bar click."
 	(setq before-scroll (or before-scroll (point)))
 	(cond
 	 ((eq part 'before-handle)
-	  (scroll-right 4))
+	  (scroll-right (* bidi-factor 4)))
 	 ((eq part 'after-handle)
-	  (scroll-left 4))
+	  (scroll-left (* bidi-factor 4)))
 	 ((eq part 'ratio)
 	  (let* ((portion-whole (nth 2 end-position))
 		 (columns (scroll-bar-scale portion-whole
 					    (1- (window-width)))))
 	    (scroll-right
-	     (cond
-	      ((not (zerop columns))
-	       columns)
-	      ((< (car portion-whole) 0) -1)
-	      (t 1)))))
+	     (* (cond
+		 ((not (zerop columns))
+		  columns)
+		 ((< (car portion-whole) 0) -1)
+		 (t 1))
+		bidi-factor))))
 	 ((eq part 'left)
-	  (scroll-right 1))
+	  (scroll-right (* bidi-factor 1)))
 	 ((eq part 'right)
-	  (scroll-left 1))
+	  (scroll-left (* bidi-factor 1)))
 	 ((eq part 'leftmost)
-	  (goto-char (line-beginning-position)))
+	  (goto-char (if (eq bidi-factor 1)
+			 (line-beginning-position)
+		       (line-end-position))))
 	 ((eq part 'rightmost)
-	  (goto-char (line-end-position)))
+	  (goto-char (if (eq bidi-factor 1)
+			 (line-end-position)
+		       (line-beginning-position))))
 	 ((eq part 'horizontal-handle)
 	  (scroll-bar-horizontal-drag-1 event))))
       (sit-for 0)
-- 
2.39.2