master 3eb82181fc 1/2: Fix scroll optimizations being enabled for some rows with stipples

[Po Lu]

branch: master
commit 3eb82181fc328e6503b6cff5321f201322489d3f
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Fix scroll optimizations being enabled for some rows with stipples
    
    * src/dispnew.c (update_text_area): New parameter `partial_p'.
    Set it if not enough glyphs were drawn to determine if a row
    doesn't have a stipple.
    (update_window_line): Preserve current_row->stipple_p in that
    case, after making the desired row current.
    
    * src/xterm.c (x_draw_fringe_bitmap): Set row->stipple.
---
 src/dispnew.c | 32 +++++++++++++++++++++++++++++---
 src/xterm.c   |  5 ++++-
 2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/src/dispnew.c b/src/dispnew.c
index c49c38cba8..795c928bc1 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -3907,7 +3907,8 @@ update_marginal_area (struct window *w, struct glyph_row 
*updated_row,
    Value is true if display has changed.  */
 
 static bool
-update_text_area (struct window *w, struct glyph_row *updated_row, int vpos)
+update_text_area (struct window *w, struct glyph_row *updated_row, int vpos,
+                 bool *partial_p)
 {
   struct glyph_row *current_row = MATRIX_ROW (w->current_matrix, vpos);
   struct glyph_row *desired_row = MATRIX_ROW (w->desired_matrix, vpos);
@@ -4013,6 +4014,13 @@ update_text_area (struct window *w, struct glyph_row 
*updated_row, int vpos)
                {
                  x += desired_glyph->pixel_width;
                  ++desired_glyph, ++current_glyph, ++i;
+
+                 /* Say that only a partial update was performed of
+                    the current row (i.e. not all the glyphs were
+                    drawn).  This is used to preserve the stipple_p
+                    flag of the current row inside
+                    update_window_line.  */
+                 *partial_p = true;
                }
 
              /* Consider the case that the current row contains "xxx
@@ -4084,9 +4092,15 @@ update_text_area (struct window *w, struct glyph_row 
*updated_row, int vpos)
              rif->write_glyphs (w, updated_row, start,
                                 TEXT_AREA, i - start_hpos);
              changed_p = 1;
+             *partial_p = true;
            }
        }
 
+      /* This means we will draw from the start, so no partial update
+        is being performed.  */
+      if (!i)
+       *partial_p = false;
+
       /* Write the rest.  */
       if (i < desired_row->used[TEXT_AREA])
        {
@@ -4159,7 +4173,9 @@ update_window_line (struct window *w, int vpos, bool 
*mouse_face_overwritten_p)
   struct glyph_row *current_row = MATRIX_ROW (w->current_matrix, vpos);
   struct glyph_row *desired_row = MATRIX_ROW (w->desired_matrix, vpos);
   struct redisplay_interface *rif = FRAME_RIF (XFRAME (WINDOW_FRAME (w)));
-  bool changed_p = 0;
+
+  /* partial_p is true if not all of desired_row was drawn.  */
+  bool changed_p = 0, partial_p = 0, was_stipple;
 
   /* A row can be completely invisible in case a desired matrix was
      built with a vscroll and then make_cursor_line_fully_visible shifts
@@ -4183,7 +4199,7 @@ update_window_line (struct window *w, int vpos, bool 
*mouse_face_overwritten_p)
        }
 
       /* Update the display of the text area.  */
-      if (update_text_area (w, desired_row, vpos))
+      if (update_text_area (w, desired_row, vpos, &partial_p))
        {
          changed_p = 1;
          if (current_row->mouse_face_p)
@@ -4212,7 +4228,17 @@ update_window_line (struct window *w, int vpos, bool 
*mouse_face_overwritten_p)
     }
 
   /* Update current_row from desired_row.  */
+  was_stipple = current_row->stipple_p;
   make_current (w->desired_matrix, w->current_matrix, vpos);
+
+  /* If only a partial update was performed, any stipple already
+     displayed in MATRIX_ROW (w->current_matrix, vpos) might still be
+     there, so don't hurry to clear that flag if it's not in
+     desired_row.  */
+
+  if (partial_p && was_stipple)
+    current_row->stipple_p = true;
+
   return changed_p;
 }
 
diff --git a/src/xterm.c b/src/xterm.c
index c9e2618191..10d268dc93 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -5750,7 +5750,8 @@ x_after_update_window_line (struct window *w, struct 
glyph_row *desired_row)
 }
 
 static void
-x_draw_fringe_bitmap (struct window *w, struct glyph_row *row, struct 
draw_fringe_bitmap_params *p)
+x_draw_fringe_bitmap (struct window *w, struct glyph_row *row,
+                     struct draw_fringe_bitmap_params *p)
 {
   struct frame *f = XFRAME (WINDOW_FRAME (w));
   Display *display = FRAME_X_DISPLAY (f);
@@ -5772,6 +5773,8 @@ x_draw_fringe_bitmap (struct window *w, struct glyph_row 
*row, struct draw_fring
          x_fill_rectangle (f, face->gc, p->bx, p->by, p->nx, p->ny,
                            true);
          XSetFillStyle (display, face->gc, FillSolid);
+
+         row->stipple_p = true;
        }
       else
        {