Disable scrolling optimizations when a stipple is present

* src/dispextern.h (struct glyph_row): New field `stippled_p'.
We cannot just use the contents of the glyph row, since it has
to be set in `gui_clear_end_of_line' and is more convenient to
set inside the various draw_glyph_string functions.

* src/dispnew.c (scrolling_window): Disable if a row in the
current matrix has the stipple_p flag set.

* src/xdisp.c (gui_clear_end_of_line):
* src/xterm.c (x_draw_image_glyph_string)
(x_draw_stretch_glyph_string, x_draw_glyph_string): Set
`stipple_p' if a stipple pattern was drawn.

src/dispextern.h

@@ -1075,6 +1075,9 @@ struct glyph_row
      right-to-left paragraph.  */
   bool_bf reversed_p : 1;
 
+  /* Whether or not a stipple was drawn in this row at some point.  */
+  bool_bf stipple_p : 1;
+
   /* Continuation lines width at the start of the row.  */
   int continuation_lines_width;
 

src/dispnew.c

@@ -4392,7 +4392,6 @@ add_row_entry (struct glyph_row *row)
   return entry;
 }
 
-
 /* Try to reuse part of the current display of W by scrolling lines.
    HEADER_LINE_P means W has a header line.
 
@@ -4438,6 +4437,14 @@ scrolling_window (struct window *w, int tab_line_p)
       struct glyph_row *d = MATRIX_ROW (desired_matrix, i);
       struct glyph_row *c = MATRIX_ROW (current_matrix, i);
 
+      /* If there is a row with a stipple currently on the glass, give
+	 up.  Stipples look different depending on where on the
+	 display they are drawn, so scrolling the display will produce
+	 incorrect results.  */
+
+      if (c->stipple_p)
+	return 0;
+
       if (c->enabled_p
 	  && d->enabled_p
 	  && !d->redraw_fringe_bitmaps_p
@@ -4467,6 +4474,16 @@ scrolling_window (struct window *w, int tab_line_p)
 
   first_old = first_new = i;
 
+  while (i < current_matrix->nrows - 1)
+    {
+      /* If there is a stipple after the first change, give up as
+	 well.  */
+      if (MATRIX_ROW (current_matrix, i)->stipple_p)
+	return 0;
+
+      ++i;
+    }
+
   /* Set last_new to the index + 1 of the row that reaches the
      bottom boundary in the desired matrix.  Give up if we find a
      disabled row before we reach the bottom boundary.  */

src/xdisp.c

@@ -32015,14 +32015,16 @@ gui_insert_glyphs (struct window *w, struct glyph_row *updated_row,
 
 void
 gui_clear_end_of_line (struct window *w, struct glyph_row *updated_row,
-		     enum glyph_row_area updated_area, int to_x)
+		       enum glyph_row_area updated_area, int to_x)
 {
   struct frame *f;
   int max_x, min_y, max_y;
   int from_x, from_y, to_y;
+  struct face *face;
 
   eassert (updated_row);
   f = XFRAME (w->frame);
+  face = FACE_FROM_ID_OR_NULL (f, DEFAULT_FACE_ID);
 
   if (updated_row->full_width_p)
     max_x = (WINDOW_PIXEL_WIDTH (w)
@@ -32074,6 +32076,9 @@ gui_clear_end_of_line (struct window *w, struct glyph_row *updated_row,
       block_input ();
       FRAME_RIF (f)->clear_frame_area (f, from_x, from_y,
                                        to_x - from_x, to_y - from_y);
+
+      if (face && !updated_row->stipple_p)
+	updated_row->stipple_p = face->stipple;
       unblock_input ();
     }
 }

src/xterm.c

@@ -8052,6 +8052,9 @@ x_draw_image_glyph_string (struct glyph_string *s)
       || s->img->pixmap == 0
       || s->width != s->background_width)
     {
+      if (s->stippled_p)
+	s->row->stipple_p = true;
+
 #ifndef USE_CAIRO
       if (s->img->mask)
 	{
@@ -8232,6 +8235,8 @@ x_draw_stretch_glyph_string (struct glyph_string *s)
 	      XSetFillStyle (display, gc, FillOpaqueStippled);
 	      x_fill_rectangle (s->f, gc, x, y, w, h, true);
 	      XSetFillStyle (display, gc, FillSolid);
+
+	      s->row->stipple_p = true;
 	    }
 	  else
 	    {
@@ -8258,8 +8263,13 @@ x_draw_stretch_glyph_string (struct glyph_string *s)
 	  background_width -= text_left_x - x;
 	  x = text_left_x;
 	}
+
+      if (!s->row->stipple_p)
+	s->row->stipple_p = s->stippled_p;
+
       if (background_width > 0)
-	x_draw_glyph_string_bg_rect (s, x, s->y, background_width, s->height);
+	x_draw_glyph_string_bg_rect (s, x, s->y,
+				     background_width, s->height);
     }
 
   s->background_filled_p = true;
@@ -8708,6 +8718,14 @@ x_draw_glyph_string (struct glyph_string *s)
   /* Reset clipping.  */
   x_reset_clip_rectangles (s->f, s->gc);
   s->num_clips = 0;
+
+  /* Set the stippled flag that tells redisplay whether or not a
+     stipple was actually draw.  */
+
+  if (s->first_glyph->type != STRETCH_GLYPH
+      && s->first_glyph->type != IMAGE_GLYPH
+      && !s->row->stipple_p)
+    s->row->stipple_p = s->stippled_p;
 }
 
 /* Shift display to make room for inserted glyphs.   */