Preliminary attempt to fix horizontal scroll bar dragging with bidi text.

* w32term.c (w32_horizontal_scroll_bar_handle_click): In y part
of emacs_event return length from si.nPage to si.nMax.
* xdisp.c (set_horizontal_scroll_bar): For right-to-left text
interchange start and end of thumb.
* scroll-bar.el (scroll-bar-horizontal-drag-1): Use cdr of
portion-whole for scrolling right-to-left text.

3 files changed, 31 insertions, 13 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 91b72e479d7..8e6e75e8b53 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,10 @@
+2014-08-16  Martin Rudalics  <rudalics@gmx.at>
+
+        * w32term.c (w32_horizontal_scroll_bar_handle_click): In y part
+        of emacs_event return length from si.nPage to si.nMax.
+        * xdisp.c (set_horizontal_scroll_bar): For right-to-left text
+        interchange start and end of thumb.
+
 2014-08-15  Ken Brown  <kbrown@cornell.edu>
 
         * gmalloc.c (_malloc_mutex, _aligned_blocks_mutex) [CYGWIN]: Use
diff --git a/src/w32term.c b/src/w32term.c
index dfda29fb903..4eff5ab4cdd 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -4272,15 +4272,15 @@ w32_horizontal_scroll_bar_handle_click (struct scroll_bar *bar, W32Msg *msg,
 
   {
     int left_range = HORIZONTAL_SCROLL_BAR_LEFT_RANGE (f, bar->width);
-    int x;
+    int x, y;
     int dragging = bar->dragging;
     SCROLLINFO si;
 
     si.cbSize = sizeof (si);
-    si.fMask = SIF_POS;
-
+    si.fMask = SIF_POS | SIF_PAGE | SIF_RANGE;
     GetScrollInfo ((HWND) msg->msg.lParam, SB_CTL, &si);
     x = si.nPos;
+    y = si.nMax - si.nPos - si.nPage;
 
     bar->dragging = 0;
     FRAME_DISPLAY_INFO (f)->last_mouse_scroll_bar_pos = msg->msg.wParam;
@@ -4354,7 +4354,7 @@ w32_horizontal_scroll_bar_handle_click (struct scroll_bar *bar, W32Msg *msg,
       }
 
     XSETINT (emacs_event->x, x);
-    XSETINT (emacs_event->y, left_range);
+    XSETINT (emacs_event->y, y);
 
     return TRUE;
   }
diff --git a/src/xdisp.c b/src/xdisp.c
index fe16b2c6a07..c46b4159de0 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -15779,7 +15779,7 @@ set_vertical_scroll_bar (struct window *w)
 void
 set_horizontal_scroll_bar (struct window *w)
 {
-  int start, end, whole, box_width;
+  int start, end, whole, portion;
 
   if (!MINI_WINDOW_P (w)
       || (w == XWINDOW (minibuf_window)
@@ -15806,14 +15806,25 @@ set_horizontal_scroll_bar (struct window *w)
                           MOVE_TO_POS | MOVE_TO_X | MOVE_TO_Y); */
 
       start = w->hscroll * FRAME_COLUMN_WIDTH (WINDOW_XFRAME (w));
-      box_width = window_box_width (w, TEXT_AREA);
-      end = start + box_width;
+      end = start + window_box_width (w, TEXT_AREA);
+      portion = end - start;
+      /* After enlarging a horizontally scrolled window such that it
+         gets at least as wide as the text it contains, make sure that
+         the thumb doesn't fill the entire scroll bar so we can still
+         drag it back to see the entire text.  */
+      whole = max (whole, end);
 
-      /* The following is needed to ensure that if after maximizing a
-         window we get hscroll > 0, we can still drag the thumb to the
-         left.  */
-      whole = max (whole, w->hscroll + box_width);
-      whole = max (whole, end - start);
+      if (it.bidi_p)
+        {
+          Lisp_Object pdir;
+
+          pdir = Fcurrent_bidi_paragraph_direction (Qnil);
+          if (EQ (pdir, Qright_to_left))
+            {
+              start = whole - end;
+              end = start + portion;
+            }
+        }
 
       if (old_buffer)
         set_buffer_internal (old_buffer);
@@ -15826,7 +15837,7 @@ set_horizontal_scroll_bar (struct window *w)
   /* Indicate what this scroll bar ought to be displaying now.  */
   if (FRAME_TERMINAL (XFRAME (w->frame))->set_horizontal_scroll_bar_hook)
     (*FRAME_TERMINAL (XFRAME (w->frame))->set_horizontal_scroll_bar_hook)
-      (w, end - start, whole, start);
+      (w, portion, whole, start);
 }