[Emacs-diffs] emacs-24 r117415: Fix hscroll of R2L lines that begin with a TAB or another wide glyph.

[Eli Zaretskii]

------------------------------------------------------------
revno: 117415
revision-id: address@hidden
parent: address@hidden
committer: Eli Zaretskii <address@hidden>
branch nick: emacs-24
timestamp: Tue 2014-07-29 11:19:29 +0300
message:
  Fix hscroll of R2L lines that begin with a TAB or another wide glyph.
  
   src/xdisp.c (append_stretch_glyph): In a R2L glyph row, decrease the
   pixel width of the first glyph that is hscrolled from display.
   (display_line): In R2L glyph rows, don't give a negative offset to
   row->x when the first glyph begins before first_visible_x.
modified:
  src/ChangeLog                  changelog-20091113204419-o5vbwnq5f7feedwu-1438
  src/xdisp.c                    xdisp.c-20091113204419-o5vbwnq5f7feedwu-240

=== modified file 'src/ChangeLog'
--- a/src/ChangeLog     2014-07-29 08:08:04 +0000
+++ b/src/ChangeLog     2014-07-29 08:19:29 +0000
@@ -1,3 +1,11 @@
+2014-07-29  Eli Zaretskii  <address@hidden>
+
+       Fix hscroll of R2L lines that begin with a TAB or another wide glyph.
+       * xdisp.c (append_stretch_glyph): In a R2L glyph row, decrease the
+       pixel width of the first glyph that is hscrolled from display.
+       (display_line): In R2L glyph rows, don't give a negative offset to
+       row->x when the first glyph begins before first_visible_x.
+
 2014-07-29  Andreas Schwab  <address@hidden>
 
        * macros.c (Fstart_kbd_macro): Initialize kbd_macro_ptr and

=== modified file 'src/xdisp.c'
--- a/src/xdisp.c       2014-07-28 13:09:02 +0000
+++ b/src/xdisp.c       2014-07-29 08:19:29 +0000
@@ -20188,7 +20188,12 @@
                                  it->max_phys_ascent + it->max_phys_descent);
          row->extra_line_spacing = max (row->extra_line_spacing,
                                         it->max_extra_line_spacing);
-         if (it->current_x - it->pixel_width < it->first_visible_x)
+         if (it->current_x - it->pixel_width < it->first_visible_x
+             /* In R2L rows, we arrange in extend_face_to_end_of_line
+                to add a right offset to the line, by a suitable
+                change to the stretch glyph that is the leftmost
+                glyph of the line.  */
+             && !row->reversed_p)
            row->x = x - it->first_visible_x;
          /* Record the maximum and minimum buffer positions seen so
             far in glyphs that will be displayed by this row.  */
@@ -20402,9 +20407,13 @@
                  if (it->bidi_p)
                    RECORD_MAX_MIN_POS (it);
 
-                 if (x < it->first_visible_x)
+                 if (x < it->first_visible_x && !row->reversed_p)
                    /* Glyph is partially visible, i.e. row starts at
-                      negative X position.  */
+                      negative X position.  Don't do that in R2L
+                      rows, where we arrange to add a right offset to
+                      the line in extend_face_to_end_of_line, by a
+                      suitable change to the stretch glyph that is
+                      the leftmost glyph of the line.  */
                    row->x = x - it->first_visible_x;
                }
              else
@@ -25295,6 +25304,24 @@
          for (g = glyph - 1; g >= it->glyph_row->glyphs[area]; g--)
            g[1] = *g;
          glyph = it->glyph_row->glyphs[area];
+
+         /* Decrease the width of the first glyph of the row that
+            begins before first_visible_x (e.g., due to hscroll).
+            This is so the overall width of the row becomes smaller
+            by the scroll amount, and the stretch glyph appended by
+            extend_face_to_end_of_line will be wider, to shift the
+            row glyphs to the right.  (In L2R rows, the corresponding
+            left-shift effect is accomplished by setting row->x to a
+            negative value, which won't work with R2L rows.)
+
+            This must leave us with a positive value of WIDTH, since
+            otherwise the call to move_it_in_display_line_to at the
+            beginning of display_line would have got past the entire
+            first glyph, and then it->current_x would have been
+            greater or equal to it->first_visible_x.  */
+         if (it->current_x < it->first_visible_x)
+           width -= it->first_visible_x - it->current_x;
+         eassert (width > 0);
        }
       glyph->charpos = CHARPOS (it->position);
       glyph->object = object;