Fix bug #17969 with vertical-motion through continuation lines with TABs.

 src/xdisp.c (move_it_to): Adjust calculation of line_start_x to what
 x_produce_glyphs does when it generates a stretch glyph that
 represents a TAB.

2 files changed, 25 insertions, 0 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 89621bd54ec..d2f1999b546 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2014-07-08  Eli Zaretskii  <eliz@gnu.org>
+
+	* xdisp.c (move_it_to): Adjust calculation of line_start_x to what
+	x_produce_glyphs does when it generates a stretch glyph that
+	represents a TAB.  (Bug#17969)
+
 2014-07-05  Eli Zaretskii  <eliz@gnu.org>
 
 	* xdisp.c (pos_visible_p): If CHARPOS is at beginning of window,
diff --git a/src/xdisp.c b/src/xdisp.c
index 28752a42cb9..61d1fa24c68 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -9250,6 +9250,25 @@ move_it_to (struct it *it, ptrdiff_t to_charpos, int to_x, int to_y, int to_vpos
 		{
 		  line_start_x = it->current_x + it->pixel_width
 		    - it->last_visible_x;
+		  if (FRAME_WINDOW_P (it->f))
+		    {
+		      struct face *face = FACE_FROM_ID (it->f, it->face_id);
+		      struct font *face_font = face->font;
+
+		      /* When display_line produces a continued line
+			 that ends in a TAB, it skips a tab stop that
+			 is closer than the font's space character
+			 width (see x_produce_glyphs where it produces
+			 the stretch glyph which represents a TAB).
+			 We need to reproduce the same logic here.  */
+		      eassert (face_font);
+		      if (face_font)
+			{
+			  if (line_start_x < face_font->space_width)
+			    line_start_x
+			      += it->tab_width * face_font->space_width;
+			}
+		    }
 		  set_iterator_to_next (it, 0);
 		}
 	    }