Fix fallout from "Qnil is zero" change in the display engine. (Bug#19535)

 src/xdisp.c (next_element_from_c_string): Use Lisp integer zero as
 the object.
 (set_cursor_from_row, try_cursor_movement, dump_glyph)
 (insert_left_trunc_glyphs, append_space_for_newline)
 (extend_face_to_end_of_line, highlight_trailing_whitespace)
 (find_row_edges, ROW_GLYPH_NEWLINE_P, Fmove_point_visually)
 (Fbidi_resolved_levels, produce_special_glyphs)
 (rows_from_pos_range, mouse_face_from_buffer_pos)
 (note_mouse_highlight): Use nil as the object for glyphs inserted
 by the display engine, and test with NILP instead of INTEGERP.
 src/w32fns.c (Fx_show_tip): Use NILP to test for glyphs inserted by
 the display engine.
 src/xfns.c (Fx_show_tip): Use NILP to test for glyphs inserted by
 the display engine.
 src/dispextern.h (struct glyph, struct it): Update comments for the
 OBJECT members.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/w32fns.c b/src/w32fns.c
index 38571d3ec21..ced3d87dd66 100644
--- a/src/w32fns.c
+++ b/src/w32fns.c
@@ -6128,7 +6128,7 @@ Text larger than the specified size is clipped.  */)
                  place the cursor there.  Don't include the width of
                  this glyph.  */
               last = &row->glyphs[TEXT_AREA][row->used[TEXT_AREA] - 1];
-              if (INTEGERP (last->object))
+              if (NILP (last->object))
                 row_width -= last->pixel_width;
             }
           else
@@ -6138,7 +6138,7 @@ Text larger than the specified size is clipped.  */)
                  Don't count that glyph.  */
               struct glyph *g = row->glyphs[TEXT_AREA];
 
-              if (g->type == STRETCH_GLYPH && INTEGERP (g->object))
+              if (g->type == STRETCH_GLYPH && NILP (g->object))
                 {
                   row_width -= g->pixel_width;
                   seen_reversed_p = 1;
@@ -6187,7 +6187,7 @@ Text larger than the specified size is clipped.  */)
           if (row->used[TEXT_AREA] && !row->reversed_p)
             {
               last = &row->glyphs[TEXT_AREA][row->used[TEXT_AREA] - 1];
-              if (INTEGERP (last->object))
+              if (NILP (last->object))
                 row_width -= last->pixel_width;
             }