Fix visual-order cursor movement when lines are truncated

* src/xdisp.c (Fmove_point_visually): When lines are truncated,
simulate display in a window of infinite width, to allow move_it_*
functions reach positions outside of normal window dimensions.
Remove code that tried to handle a subset of these situations by
manual iteration of buffer text.  (Bug#17777)

1 files changed, 10 insertions, 21 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index 16a7a64c89b..2be057fd211 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -21291,6 +21291,14 @@ Value is the new character position of point.  */)
       /* Setup the arena.  */
       SET_TEXT_POS (pt, PT, PT_BYTE);
       start_display (&it, w, pt);
+      /* When lines are truncated, we could be called with point
+         outside of the windows edges, in which case move_it_*
+         functions either prematurely stop at window's edge or jump to
+         the next screen line, whereas we rely below on our ability to
+         reach point, in order to start from its X coordinate.  So we
+         need to disregard the window's horizontal extent in that case.  */
+      if (it.line_wrap == TRUNCATE)
+        it.last_visible_x = INFINITY;
 
       if (it.cmp_it.id < 0
           && it.method == GET_FROM_STRING
@@ -21382,6 +21390,8 @@ Value is the new character position of point.  */)
           if (pt_x > 0)
             {
               start_display (&it, w, pt);
+              if (it.line_wrap == TRUNCATE)
+                it.last_visible_x = INFINITY;
               reseat_at_previous_visible_line_start (&it);
               it.current_x = it.current_y = it.hpos = 0;
               if (pt_vpos != 0)
@@ -21494,27 +21504,6 @@ Value is the new character position of point.  */)
       if (it.current_x != target_x)
         move_it_in_display_line_to (&it, ZV, target_x, MOVE_TO_POS | MOVE_TO_X);
 
-      /* When lines are truncated, the above loop will stop at the
-         window edge.  But we want to get to the end of line, even if
-         it is beyond the window edge; automatic hscroll will then
-         scroll the window to show point as appropriate.  */
-      if (target_is_eol_p && it.line_wrap == TRUNCATE
-          && get_next_display_element (&it))
-        {
-          struct text_pos new_pos = it.current.pos;
-
-          while (!ITERATOR_AT_END_OF_LINE_P (&it))
-            {
-              set_iterator_to_next (&it, false);
-              if (it.method == GET_FROM_BUFFER)
-                new_pos = it.current.pos;
-              if (!get_next_display_element (&it))
-                break;
-            }
-
-          it.current.pos = new_pos;
-        }
-
       /* If we ended up in a display string that covers point, move to
          buffer position to the right in the visual order.  */
       if (dir > 0)