Support horizontal scrolling of bidirectional text.

 lisp/scroll-bar.el (scroll-bar-toolkit-horizontal-scroll): Add
 rudimentary support for bidirectional text.

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)