Re: Changes in frame/window code

[Eli Zaretskii]

> Date: Tue, 29 Jul 2014 12:41:02 +0300
> From: Eli Zaretskii <address@hidden>
> Cc: address@hidden, address@hidden
> 
> >  > You need to reverse the meaning of START and END for the R2L case:
> >  >
> >  >     end = whole - w->hscroll * FRAME_COLUMN_WIDTH (WINDOW_XFRAME (w));
> >  >     start = end - box_width;
> >  >
> >  > (Note that current-bidi-paragraph-direction returns the results at
> >  > buffer's point, so you will need to temporarily go to the window's
> >  > point marker.)
> > 
> > As soon as you have some spare time (I know you never do) please try it.
> 
> I can only try this on MS-Windows.

The patch below almost works.  "Almost" because of 2 issues that still
need to be taken care of:

 . As soon as I click on the scroll-bar thumb, which is correctly
   drawn flushed all the way to the right when point is an a R2L line,
   the scroll bar "jumps" to the left edge.  Where's the code which
   does that?

 . The code below is for the selected window, where point is up to
   date.  But what about non-selected windows, should we use
   window-point there?

=== modified file 'src/xdisp.c'
--- src/xdisp.c 2014-07-27 13:21:30 +0000
+++ src/xdisp.c 2014-07-29 10:17:58 +0000
@@ -15814,6 +15814,17 @@ set_horizontal_scroll_bar (struct window
         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))
+           {
+             end = whole - w->hscroll * FRAME_COLUMN_WIDTH (WINDOW_XFRAME (w));
+             start = end - box_width;
+           }
+       }
 
       if (old_buffer)
        set_buffer_internal (old_buffer);