Make all NS drawing be done from drawRect

See bug#31904 and bug#32812.

* src/nsterm.m (ns_update_begin): Don't lock focus, only clip if there
is already a view focused.
(ns_update_end): Don't mess with view focusing any more.
(ns_focus): Only clip drawing if there is already a focused view,
otherwise mark area dirty for later drawing.  Renamed ns_clip_to_rect.
All callers changed.
(ns_unfocus): Don't unfocus the view any more.  Renamed
ns_reset_clipping. All callers changed.
(ns_clip_to_row): Update to match ns_clip_to_rect.
(ns_clear_frame):
(ns_clear_frame_area):
(ns_draw_fringe_bitmap):
(ns_draw_window_cursor):
(ns_draw_vertical_window_border):
(ns_draw_window_divider):
(ns_dumpglyphs_stretch):
(ns_draw_glyph_string): Only draw if ns_focus or ns_clip_to_row
return YES.
(ns_copy_bits): Remove superfluous calls to ns_(un)focus.
(ns_flush_display): New function.

1 files changed, 376 insertions, 391 deletions

diff --git a/src/nsterm.m b/src/nsterm.m
index 5ed71c9f8f1..954020dcde9 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -276,12 +276,7 @@ struct ns_display_info *x_display_list; /* Chain of existing displays */
 long context_menu_value = 0;
 
 /* display update */
-static struct frame *ns_updating_frame;
-static NSView *focus_view = NULL;
 static int ns_window_num = 0;
-#ifdef NS_IMPL_GNUSTEP
-static NSRect uRect;            // TODO: This is dead, remove it?
-#endif
 static BOOL gsaved = NO;
 static BOOL ns_fake_keydown = NO;
 #ifdef NS_IMPL_COCOA
@@ -1039,12 +1034,13 @@ ns_update_begin (struct frame *f)
    external (RIF) call; whole frame, called before update_window_begin
    -------------------------------------------------------------------------- */
 {
+#ifdef NS_IMPL_COCOA
   EmacsView *view = FRAME_NS_VIEW (f);
+
   NSTRACE_WHEN (NSTRACE_GROUP_UPDATES, "ns_update_begin");
 
   ns_update_auto_hide_menu_bar ();
 
-#ifdef NS_IMPL_COCOA
   if ([view isFullscreen] && [view fsIsNative])
   {
     // Fix reappearing tool bar in fullscreen for Mac OS X 10.7
@@ -1053,36 +1049,29 @@ ns_update_begin (struct frame *f)
     if (! tbar_visible != ! [toolbar isVisible])
       [toolbar setVisible: tbar_visible];
   }
-#endif
-
-  ns_updating_frame = f;
-  [view lockFocus];
 
   /* drawRect may have been called for say the minibuffer, and then clip path
      is for the minibuffer.  But the display engine may draw more because
      we have set the frame as garbaged.  So reset clip path to the whole
      view.  */
-#ifdef NS_IMPL_COCOA
-  {
-    NSBezierPath *bp;
-    NSRect r = [view frame];
-    NSRect cr = [[view window] frame];
-    /* If a large frame size is set, r may be larger than the window frame
-       before constrained.  In that case don't change the clip path, as we
-       will clear in to the tool bar and title bar.  */
-    if (r.size.height
-        + FRAME_NS_TITLEBAR_HEIGHT (f)
-        + FRAME_TOOLBAR_HEIGHT (f) <= cr.size.height)
-      {
-        bp = [[NSBezierPath bezierPathWithRect: r] retain];
-        [bp setClip];
-        [bp release];
-      }
-  }
-#endif
-
-#ifdef NS_IMPL_GNUSTEP
-  uRect = NSMakeRect (0, 0, 0, 0);
+  /* FIXME: I don't think we need to do this.  */
+  if ([NSView focusView] == FRAME_NS_VIEW (f))
+    {
+      NSBezierPath *bp;
+      NSRect r = [view frame];
+      NSRect cr = [[view window] frame];
+      /* If a large frame size is set, r may be larger than the window frame
+         before constrained.  In that case don't change the clip path, as we
+         will clear in to the tool bar and title bar.  */
+      if (r.size.height
+          + FRAME_NS_TITLEBAR_HEIGHT (f)
+          + FRAME_TOOLBAR_HEIGHT (f) <= cr.size.height)
+        {
+          bp = [[NSBezierPath bezierPathWithRect: r] retain];
+          [bp setClip];
+          [bp release];
+        }
+    }
 #endif
 }
 
@@ -1164,99 +1153,66 @@ ns_update_end (struct frame *f)
    external (RIF) call; for whole frame, called after update_window_end
    -------------------------------------------------------------------------- */
 {
-  EmacsView *view = FRAME_NS_VIEW (f);
-
   NSTRACE_WHEN (NSTRACE_GROUP_UPDATES, "ns_update_end");
 
 /*   if (f == MOUSE_HL_INFO (f)->mouse_face_mouse_frame) */
   MOUSE_HL_INFO (f)->mouse_face_defer = 0;
-
-  block_input ();
-
-  [view unlockFocus];
-  [[view window] flushWindow];
-
-  unblock_input ();
-  ns_updating_frame = NULL;
 }
 
-static void
-ns_focus (struct frame *f, NSRect *r, int n)
+
+static BOOL
+ns_clip_to_rect (struct frame *f, NSRect *r, int n)
 /* --------------------------------------------------------------------------
-   Internal: Focus on given frame.  During small local updates this is used to
-     draw, however during large updates, ns_update_begin and ns_update_end are
-     called to wrap the whole thing, in which case these calls are stubbed out.
-     Except, on GNUstep, we accumulate the rectangle being drawn into, because
-     the back end won't do this automatically, and will just end up flushing
-     the entire window.
+   Clip the drawing area to rectangle r in frame f.  If drawing is not
+   currently possible mark r as dirty and return NO, otherwise return
+   YES.
    -------------------------------------------------------------------------- */
 {
-  NSTRACE_WHEN (NSTRACE_GROUP_FOCUS, "ns_focus");
-  if (r != NULL)
+  NSTRACE_WHEN (NSTRACE_GROUP_FOCUS, "ns_clip_to_rect");
+  if (r)
     {
       NSTRACE_RECT ("r", *r);
-    }
 
-  if (f != ns_updating_frame)
-    {
-      NSView *view = FRAME_NS_VIEW (f);
-      if (view != focus_view)
+      if ([NSView focusView] == FRAME_NS_VIEW (f))
         {
-          if (focus_view != NULL)
-            {
-              [focus_view unlockFocus];
-              [[focus_view window] flushWindow];
-/*debug_lock--; */
-            }
+          [[NSGraphicsContext currentContext] saveGraphicsState];
+          if (n == 2)
+            NSRectClipList (r, 2);
+          else
+            NSRectClip (*r);
+          gsaved = YES;
 
-          if (view)
-            [view lockFocus];
-          focus_view = view;
-/*if (view) debug_lock++; */
+          return YES;
         }
-    }
-
-  /* clipping */
-  if (r)
-    {
-      [[NSGraphicsContext currentContext] saveGraphicsState];
-      if (n == 2)
-        NSRectClipList (r, 2);
       else
-        NSRectClip (*r);
-      gsaved = YES;
+        {
+          NSView *view = FRAME_NS_VIEW (f);
+          int i;
+          for (i = 0 ; i < n ; i++)
+            [view setNeedsDisplayInRect:r[i]];
+        }
     }
+
+  return NO;
 }
 
 
 static void
-ns_unfocus (struct frame *f)
-/* --------------------------------------------------------------------------
-     Internal: Remove focus on given frame
-   -------------------------------------------------------------------------- */
+ns_reset_clipping (struct frame *f)
+/* Internal: Restore the previous graphics state, unsetting any
+   clipping areas.  */
 {
-  NSTRACE_WHEN (NSTRACE_GROUP_FOCUS, "ns_unfocus");
+  NSTRACE_WHEN (NSTRACE_GROUP_FOCUS, "ns_reset_clipping");
 
   if (gsaved)
     {
       [[NSGraphicsContext currentContext] restoreGraphicsState];
       gsaved = NO;
     }
-
-  if (f != ns_updating_frame)
-    {
-      if (focus_view != NULL)
-        {
-          [focus_view unlockFocus];
-          [[focus_view window] flushWindow];
-          focus_view = NULL;
-/*debug_lock--; */
-        }
-    }
 }
 
 
-static void
+static BOOL
 ns_clip_to_row (struct window *w, struct glyph_row *row,
                 enum glyph_row_area area, BOOL gc)
 /* --------------------------------------------------------------------------
@@ -1275,7 +1231,19 @@ ns_clip_to_row (struct window *w, struct glyph_row *row,
   clip_rect.size.width = window_width;
   clip_rect.size.height = row->visible_height;
 
-  ns_focus (f, &clip_rect, 1);
+  return ns_clip_to_rect (f, &clip_rect, 1);
+}
+
+
+static void
+ns_flush_display (struct frame *f)
+/* Force the frame to redisplay.  If areas have previously been marked
+   dirty by setNeedsDisplayInRect (in ns_clip_to_rect), then this will call
+   draw_rect: which will "expose" those areas.  */
+{
+  block_input ();
+  [FRAME_NS_VIEW (f) displayIfNeeded];
+  unblock_input ();
 }
 
 
@@ -2699,14 +2667,16 @@ ns_clear_frame (struct frame *f)
   r = [view bounds];
 
   block_input ();
-  ns_focus (f, &r, 1);
-  [ns_lookup_indexed_color (NS_FACE_BACKGROUND
-                            (FACE_FROM_ID (f, DEFAULT_FACE_ID)), f) set];
-  NSRectFill (r);
-  ns_unfocus (f);
-
-  /* as of 2006/11 or so this is now needed */
-  ns_redraw_scroll_bars (f);
+  if (ns_clip_to_rect (f, &r, 1))
+    {
+      [ns_lookup_indexed_color (NS_FACE_BACKGROUND
+                                (FACE_FROM_ID (f, DEFAULT_FACE_ID)), f) set];
+      NSRectFill (r);
+      ns_reset_clipping (f);
+
+      /* as of 2006/11 or so this is now needed */
+      ns_redraw_scroll_bars (f);
+    }
   unblock_input ();
 }
 
@@ -2727,13 +2697,14 @@ ns_clear_frame_area (struct frame *f, int x, int y, int width, int height)
   NSTRACE_WHEN (NSTRACE_GROUP_UPDATES, "ns_clear_frame_area");
 
   r = NSIntersectionRect (r, [view frame]);
-  ns_focus (f, &r, 1);
-  [ns_lookup_indexed_color (NS_FACE_BACKGROUND (face), f) set];
+  if (ns_clip_to_rect (f, &r, 1))
+    {
+      [ns_lookup_indexed_color (NS_FACE_BACKGROUND (face), f) set];
 
-  NSRectFill (r);
+      NSRectFill (r);
 
-  ns_unfocus (f);
-  return;
+      ns_reset_clipping (f);
+    }
 }
 
 static void
@@ -2745,11 +2716,11 @@ ns_copy_bits (struct frame *f, NSRect src, NSRect dest)
     {
       hide_bell();              // Ensure the bell image isn't scrolled.
 
-      ns_focus (f, &dest, 1);
+      /* FIXME: scrollRect:by: is deprecated in macOS 10.14.  There is
+         no obvious replacement so we may have to come up with our own.  */
       [FRAME_NS_VIEW (f) scrollRect: src
                                  by: NSMakeSize (dest.origin.x - src.origin.x,
                                                  dest.origin.y - src.origin.y)];
-      ns_unfocus (f);
     }
 }
 
@@ -2960,85 +2931,86 @@ ns_draw_fringe_bitmap (struct window *w, struct glyph_row *row,
     }
 
   /* Must clip because of partially visible lines.  */
-  ns_clip_to_row (w, row, ANY_AREA, YES);
-
-  if (!p->overlay_p)
+  if (ns_clip_to_row (w, row, ANY_AREA, YES))
     {
-      int bx = p->bx, by = p->by, nx = p->nx, ny = p->ny;
-
-      if (bx >= 0 && nx > 0)
+      if (!p->overlay_p)
         {
-          NSRect r = NSMakeRect (bx, by, nx, ny);
-          NSRectClip (r);
-          [ns_lookup_indexed_color (face->background, f) set];
-          NSRectFill (r);
-        }
-    }
+          int bx = p->bx, by = p->by, nx = p->nx, ny = p->ny;
 
-  if (p->which)
-    {
-      NSRect r = NSMakeRect (p->x, p->y, p->wd, p->h);
-      EmacsImage *img = bimgs[p->which - 1];
-
-      if (!img)
-        {
-          // Note: For "periodic" images, allocate one EmacsImage for
-          // the base image, and use it for all dh:s.
-          unsigned short *bits = p->bits;
-          int full_height = p->h + p->dh;
-          int i;
-          unsigned char *cbits = xmalloc (full_height);
-
-          for (i = 0; i < full_height; i++)
-            cbits[i] = bits[i];
-          img = [[EmacsImage alloc] initFromXBM: cbits width: 8
-                                         height: full_height
-                                             fg: 0 bg: 0];
-          bimgs[p->which - 1] = img;
-          xfree (cbits);
+          if (bx >= 0 && nx > 0)
+            {
+              NSRect r = NSMakeRect (bx, by, nx, ny);
+              NSRectClip (r);
+              [ns_lookup_indexed_color (face->background, f) set];
+              NSRectFill (r);
+            }
         }
 
-      NSTRACE_RECT ("r", r);
+      if (p->which)
+        {
+          NSRect r = NSMakeRect (p->x, p->y, p->wd, p->h);
+          EmacsImage *img = bimgs[p->which - 1];
 
-      NSRectClip (r);
-      /* Since we composite the bitmap instead of just blitting it, we need
-         to erase the whole background. */
-      [ns_lookup_indexed_color(face->background, f) set];
-      NSRectFill (r);
+          if (!img)
+            {
+              // Note: For "periodic" images, allocate one EmacsImage for
+              // the base image, and use it for all dh:s.
+              unsigned short *bits = p->bits;
+              int full_height = p->h + p->dh;
+              int i;
+              unsigned char *cbits = xmalloc (full_height);
+
+              for (i = 0; i < full_height; i++)
+                cbits[i] = bits[i];
+              img = [[EmacsImage alloc] initFromXBM: cbits width: 8
+                                             height: full_height
+                                                 fg: 0 bg: 0];
+              bimgs[p->which - 1] = img;
+              xfree (cbits);
+            }
 
-      {
-        NSColor *bm_color;
-        if (!p->cursor_p)
-          bm_color = ns_lookup_indexed_color(face->foreground, f);
-        else if (p->overlay_p)
-          bm_color = ns_lookup_indexed_color(face->background, f);
-        else
-          bm_color = f->output_data.ns->cursor_color;
-        [img setXBMColor: bm_color];
-      }
+          NSTRACE_RECT ("r", r);
 
-#ifdef NS_IMPL_COCOA
-      // Note: For periodic images, the full image height is "h + hd".
-      // By using the height h, a suitable part of the image is used.
-      NSRect fromRect = NSMakeRect(0, 0, p->wd, p->h);
+          NSRectClip (r);
+          /* Since we composite the bitmap instead of just blitting it, we need
+             to erase the whole background.  */
+          [ns_lookup_indexed_color(face->background, f) set];
+          NSRectFill (r);
 
-      NSTRACE_RECT ("fromRect", fromRect);
+          {
+            NSColor *bm_color;
+            if (!p->cursor_p)
+              bm_color = ns_lookup_indexed_color(face->foreground, f);
+            else if (p->overlay_p)
+              bm_color = ns_lookup_indexed_color(face->background, f);
+            else
+              bm_color = f->output_data.ns->cursor_color;
+            [img setXBMColor: bm_color];
+          }
 
-      [img drawInRect: r
-              fromRect: fromRect
-             operation: NSCompositingOperationSourceOver
-              fraction: 1.0
-           respectFlipped: YES
-                hints: nil];
+#ifdef NS_IMPL_COCOA
+          // Note: For periodic images, the full image height is "h + hd".
+          // By using the height h, a suitable part of the image is used.
+          NSRect fromRect = NSMakeRect(0, 0, p->wd, p->h);
+
+          NSTRACE_RECT ("fromRect", fromRect);
+
+          [img drawInRect: r
+                 fromRect: fromRect
+                operation: NSCompositingOperationSourceOver
+                 fraction: 1.0
+               respectFlipped: YES
+                    hints: nil];
 #else
-      {
-        NSPoint pt = r.origin;
-        pt.y += p->h;
-        [img compositeToPoint: pt operation: NSCompositingOperationSourceOver];
-      }
+          {
+            NSPoint pt = r.origin;
+            pt.y += p->h;
+            [img compositeToPoint: pt operation: NSCompositingOperationSourceOver];
+          }
 #endif
+        }
+      ns_reset_clipping (f);
     }
-  ns_unfocus (f);
 }
 
 
@@ -3120,67 +3092,66 @@ ns_draw_window_cursor (struct window *w, struct glyph_row *glyph_row,
   r.size.height = h;
   r.size.width = w->phys_cursor_width;
 
-  /* Prevent the cursor from being drawn outside the text area. */
-  ns_clip_to_row (w, glyph_row, TEXT_AREA, NO); /* do ns_focus(f, &r, 1); if remove */
-
-
-  face = FACE_FROM_ID_OR_NULL (f, phys_cursor_glyph->face_id);
-  if (face && NS_FACE_BACKGROUND (face)
-      == ns_index_color (FRAME_CURSOR_COLOR (f), f))
+  /* Prevent the cursor from being drawn outside the text area.  */
+  if (ns_clip_to_row (w, glyph_row, TEXT_AREA, NO))
     {
-      [ns_lookup_indexed_color (NS_FACE_FOREGROUND (face), f) set];
-      hollow_color = FRAME_CURSOR_COLOR (f);
-    }
-  else
-    [FRAME_CURSOR_COLOR (f) set];
+      face = FACE_FROM_ID_OR_NULL (f, phys_cursor_glyph->face_id);
+      if (face && NS_FACE_BACKGROUND (face)
+          == ns_index_color (FRAME_CURSOR_COLOR (f), f))
+        {
+          [ns_lookup_indexed_color (NS_FACE_FOREGROUND (face), f) set];
+          hollow_color = FRAME_CURSOR_COLOR (f);
+        }
+      else
+        [FRAME_CURSOR_COLOR (f) set];
 
 #ifdef NS_IMPL_COCOA
-  /* TODO: This makes drawing of cursor plus that of phys_cursor_glyph
-           atomic.  Cleaner ways of doing this should be investigated.
-           One way would be to set a global variable DRAWING_CURSOR
-           when making the call to draw_phys..(), don't focus in that
-           case, then move the ns_unfocus() here after that call. */
-  NSDisableScreenUpdates ();
+      /* TODO: This makes drawing of cursor plus that of phys_cursor_glyph
+         atomic.  Cleaner ways of doing this should be investigated.
+         One way would be to set a global variable DRAWING_CURSOR
+         when making the call to draw_phys..(), don't focus in that
+         case, then move the ns_reset_clipping() here after that call.  */
+      NSDisableScreenUpdates ();
 #endif
 
-  switch (cursor_type)
-    {
-    case DEFAULT_CURSOR:
-    case NO_CURSOR:
-      break;
-    case FILLED_BOX_CURSOR:
-      NSRectFill (r);
-      break;
-    case HOLLOW_BOX_CURSOR:
-      NSRectFill (r);
-      [hollow_color set];
-      NSRectFill (NSInsetRect (r, 1, 1));
-      [FRAME_CURSOR_COLOR (f) set];
-      break;
-    case HBAR_CURSOR:
-      NSRectFill (r);
-      break;
-    case BAR_CURSOR:
-      s = r;
-      /* If the character under cursor is R2L, draw the bar cursor
-         on the right of its glyph, rather than on the left.  */
-      cursor_glyph = get_phys_cursor_glyph (w);
-      if ((cursor_glyph->resolved_level & 1) != 0)
-        s.origin.x += cursor_glyph->pixel_width - s.size.width;
-
-      NSRectFill (s);
-      break;
-    }
-  ns_unfocus (f);
+      switch (cursor_type)
+        {
+        case DEFAULT_CURSOR:
+        case NO_CURSOR:
+          break;
+        case FILLED_BOX_CURSOR:
+          NSRectFill (r);
+          break;
+        case HOLLOW_BOX_CURSOR:
+          NSRectFill (r);
+          [hollow_color set];
+          NSRectFill (NSInsetRect (r, 1, 1));
+          [FRAME_CURSOR_COLOR (f) set];
+          break;
+        case HBAR_CURSOR:
+          NSRectFill (r);
+          break;
+        case BAR_CURSOR:
+          s = r;
+          /* If the character under cursor is R2L, draw the bar cursor
+             on the right of its glyph, rather than on the left.  */
+          cursor_glyph = get_phys_cursor_glyph (w);
+          if ((cursor_glyph->resolved_level & 1) != 0)
+            s.origin.x += cursor_glyph->pixel_width - s.size.width;
+
+          NSRectFill (s);
+          break;
+        }
+      ns_reset_clipping (f);
 
-  /* draw the character under the cursor */
-  if (cursor_type != NO_CURSOR)
-    draw_phys_cursor_glyph (w, glyph_row, DRAW_CURSOR);
+      /* draw the character under the cursor */
+      if (cursor_type != NO_CURSOR)
+        draw_phys_cursor_glyph (w, glyph_row, DRAW_CURSOR);
 
 #ifdef NS_IMPL_COCOA
-  NSEnableScreenUpdates ();
+      NSEnableScreenUpdates ();
 #endif
-
+    }
 }
 
 
@@ -3198,12 +3169,14 @@ ns_draw_vertical_window_border (struct window *w, int x, int y0, int y1)
 
   face = FACE_FROM_ID_OR_NULL (f, VERTICAL_BORDER_FACE_ID);
 
-  ns_focus (f, &r, 1);
-  if (face)
-    [ns_lookup_indexed_color(face->foreground, f) set];
+  if (ns_clip_to_rect (f, &r, 1))
+    {
+      if (face)
+        [ns_lookup_indexed_color(face->foreground, f) set];
 
-  NSRectFill(r);
-  ns_unfocus (f);
+      NSRectFill(r);
+      ns_reset_clipping (f);
+    }
 }
 
 
@@ -3230,39 +3203,40 @@ ns_draw_window_divider (struct window *w, int x0, int x1, int y0, int y1)
 
   NSTRACE ("ns_draw_window_divider");
 
-  ns_focus (f, &divider, 1);
-
-  if ((y1 - y0 > x1 - x0) && (x1 - x0 >= 3))
-    /* A vertical divider, at least three pixels wide: Draw first and
-       last pixels differently.  */
+  if (ns_clip_to_rect (f, &divider, 1))
     {
-      [ns_lookup_indexed_color(color_first, f) set];
-      NSRectFill(NSMakeRect (x0, y0, 1, y1 - y0));
-      [ns_lookup_indexed_color(color, f) set];
-      NSRectFill(NSMakeRect (x0 + 1, y0, x1 - x0 - 2, y1 - y0));
-      [ns_lookup_indexed_color(color_last, f) set];
-      NSRectFill(NSMakeRect (x1 - 1, y0, 1, y1 - y0));
-    }
-  else if ((x1 - x0 > y1 - y0) && (y1 - y0 >= 3))
-    /* A horizontal divider, at least three pixels high: Draw first and
-       last pixels differently.  */
-    {
-      [ns_lookup_indexed_color(color_first, f) set];
-      NSRectFill(NSMakeRect (x0, y0, x1 - x0, 1));
-      [ns_lookup_indexed_color(color, f) set];
-      NSRectFill(NSMakeRect (x0, y0 + 1, x1 - x0, y1 - y0 - 2));
-      [ns_lookup_indexed_color(color_last, f) set];
-      NSRectFill(NSMakeRect (x0, y1 - 1, x1 - x0, 1));
-    }
-  else
-    {
-      /* In any other case do not draw the first and last pixels
-         differently.  */
-      [ns_lookup_indexed_color(color, f) set];
-      NSRectFill(divider);
-    }
+      if ((y1 - y0 > x1 - x0) && (x1 - x0 >= 3))
+        /* A vertical divider, at least three pixels wide: Draw first and
+           last pixels differently.  */
+        {
+          [ns_lookup_indexed_color(color_first, f) set];
+          NSRectFill(NSMakeRect (x0, y0, 1, y1 - y0));
+          [ns_lookup_indexed_color(color, f) set];
+          NSRectFill(NSMakeRect (x0 + 1, y0, x1 - x0 - 2, y1 - y0));
+          [ns_lookup_indexed_color(color_last, f) set];
+          NSRectFill(NSMakeRect (x1 - 1, y0, 1, y1 - y0));
+        }
+      else if ((x1 - x0 > y1 - y0) && (y1 - y0 >= 3))
+        /* A horizontal divider, at least three pixels high: Draw first and
+           last pixels differently.  */
+        {
+          [ns_lookup_indexed_color(color_first, f) set];
+          NSRectFill(NSMakeRect (x0, y0, x1 - x0, 1));
+          [ns_lookup_indexed_color(color, f) set];
+          NSRectFill(NSMakeRect (x0, y0 + 1, x1 - x0, y1 - y0 - 2));
+          [ns_lookup_indexed_color(color_last, f) set];
+          NSRectFill(NSMakeRect (x0, y1 - 1, x1 - x0, 1));
+        }
+      else
+        {
+          /* In any other case do not draw the first and last pixels
+             differently.  */
+          [ns_lookup_indexed_color(color, f) set];
+          NSRectFill(divider);
+        }
 
-  ns_unfocus (f);
+      ns_reset_clipping (f);
+    }
 }
 
 static void
@@ -3846,83 +3820,84 @@ ns_dumpglyphs_stretch (struct glyph_string *s)
       n = ns_get_glyph_string_clip_rect (s, r);
       *r = NSMakeRect (s->x, s->y, s->background_width, s->height);
 
-      ns_focus (s->f, r, n);
-
-      if (s->hl == DRAW_MOUSE_FACE)
-       {
-         face = FACE_FROM_ID_OR_NULL (s->f,
-                                      MOUSE_HL_INFO (s->f)->mouse_face_face_id);
-         if (!face)
-           face = FACE_FROM_ID (s->f, MOUSE_FACE_ID);
-       }
-      else
-       face = FACE_FROM_ID (s->f, s->first_glyph->face_id);
-
-      bgCol = ns_lookup_indexed_color (NS_FACE_BACKGROUND (face), s->f);
-      fgCol = ns_lookup_indexed_color (NS_FACE_FOREGROUND (face), s->f);
-
-      for (i = 0; i < n; ++i)
+      if (ns_clip_to_rect (s->f, r, n))
         {
-          if (!s->row->full_width_p)
+          if (s->hl == DRAW_MOUSE_FACE)
             {
-              int overrun, leftoverrun;
-
-              /* truncate to avoid overwriting fringe and/or scrollbar */
-              overrun = max (0, (s->x + s->background_width)
-                             - (WINDOW_BOX_RIGHT_EDGE_X (s->w)
-                                - WINDOW_RIGHT_FRINGE_WIDTH (s->w)));
-              r[i].size.width -= overrun;
-
-              /* truncate to avoid overwriting to left of the window box */
-              leftoverrun = (WINDOW_BOX_LEFT_EDGE_X (s->w)
-                             + WINDOW_LEFT_FRINGE_WIDTH (s->w)) - s->x;
-
-              if (leftoverrun > 0)
-                {
-                  r[i].origin.x += leftoverrun;
-                  r[i].size.width -= leftoverrun;
-                }
-
-              /* XXX: Try to work between problem where a stretch glyph on
-                 a partially-visible bottom row will clear part of the
-                 modeline, and another where list-buffers headers and similar
-                 rows erroneously have visible_height set to 0.  Not sure
-                 where this is coming from as other terms seem not to show. */
-              r[i].size.height = min (s->height, s->row->visible_height);
+              face = FACE_FROM_ID_OR_NULL (s->f,
+                                           MOUSE_HL_INFO (s->f)->mouse_face_face_id);
+              if (!face)
+                face = FACE_FROM_ID (s->f, MOUSE_FACE_ID);
             }
+          else
+            face = FACE_FROM_ID (s->f, s->first_glyph->face_id);
 
-          [bgCol set];
+          bgCol = ns_lookup_indexed_color (NS_FACE_BACKGROUND (face), s->f);
+          fgCol = ns_lookup_indexed_color (NS_FACE_FOREGROUND (face), s->f);
 
-          /* NOTE: under NS this is NOT used to draw cursors, but we must avoid
-             overwriting cursor (usually when cursor on a tab) */
-          if (s->hl == DRAW_CURSOR)
+          for (i = 0; i < n; ++i)
             {
-              CGFloat x, width;
+              if (!s->row->full_width_p)
+                {
+                  int overrun, leftoverrun;
+
+                  /* truncate to avoid overwriting fringe and/or scrollbar */
+                  overrun = max (0, (s->x + s->background_width)
+                                 - (WINDOW_BOX_RIGHT_EDGE_X (s->w)
+                                    - WINDOW_RIGHT_FRINGE_WIDTH (s->w)));
+                  r[i].size.width -= overrun;
+
+                  /* truncate to avoid overwriting to left of the window box */
+                  leftoverrun = (WINDOW_BOX_LEFT_EDGE_X (s->w)
+                                 + WINDOW_LEFT_FRINGE_WIDTH (s->w)) - s->x;
+
+                    if (leftoverrun > 0)
+                      {
+                        r[i].origin.x += leftoverrun;
+                        r[i].size.width -= leftoverrun;
+                      }
+
+                    /* XXX: Try to work between problem where a stretch glyph on
+                       a partially-visible bottom row will clear part of the
+                       modeline, and another where list-buffers headers and similar
+                       rows erroneously have visible_height set to 0.  Not sure
+                       where this is coming from as other terms seem not to show.  */
+                    r[i].size.height = min (s->height, s->row->visible_height);
+                }
+
+              [bgCol set];
+
+              /* NOTE: under NS this is NOT used to draw cursors, but we must avoid
+                 overwriting cursor (usually when cursor on a tab).  */
+              if (s->hl == DRAW_CURSOR)
+                {
+                  CGFloat x, width;
 
-              x = r[i].origin.x;
-              width = s->w->phys_cursor_width;
-              r[i].size.width -= width;
-              r[i].origin.x += width;
+                  x = r[i].origin.x;
+                  width = s->w->phys_cursor_width;
+                  r[i].size.width -= width;
+                  r[i].origin.x += width;
 
-              NSRectFill (r[i]);
+                  NSRectFill (r[i]);
 
-              /* Draw overlining, etc. on the cursor. */
-              if (s->w->phys_cursor_type == FILLED_BOX_CURSOR)
-                ns_draw_text_decoration (s, face, bgCol, width, x);
+                  /* Draw overlining, etc. on the cursor.  */
+                  if (s->w->phys_cursor_type == FILLED_BOX_CURSOR)
+                    ns_draw_text_decoration (s, face, bgCol, width, x);
+                  else
+                    ns_draw_text_decoration (s, face, fgCol, width, x);
+                }
               else
-                ns_draw_text_decoration (s, face, fgCol, width, x);
-            }
-          else
-            {
-              NSRectFill (r[i]);
-            }
+                {
+                  NSRectFill (r[i]);
+                }
 
-          /* Draw overlining, etc. on the stretch glyph (or the part
-             of the stretch glyph after the cursor). */
-          ns_draw_text_decoration (s, face, fgCol, r[i].size.width,
-                                   r[i].origin.x);
+              /* Draw overlining, etc. on the stretch glyph (or the part
+                 of the stretch glyph after the cursor).  */
+              ns_draw_text_decoration (s, face, fgCol, r[i].size.width,
+                                       r[i].origin.x);
+            }
+          ns_reset_clipping (s->f);
         }
-      ns_unfocus (s->f);
       s->background_filled_p = 1;
     }
 }
@@ -4072,9 +4047,11 @@ ns_draw_glyph_string (struct glyph_string *s)
             if (next->first_glyph->type != STRETCH_GLYPH)
               {
                 n = ns_get_glyph_string_clip_rect (s->next, r);
-                ns_focus (s->f, r, n);
-                ns_maybe_dumpglyphs_background (s->next, 1);
-                ns_unfocus (s->f);
+                if (ns_clip_to_rect (s->f, r, n))
+                  {
+                    ns_maybe_dumpglyphs_background (s->next, 1);
+                    ns_reset_clipping (s->f);
+                  }
               }
             else
               {
@@ -4089,10 +4066,12 @@ ns_draw_glyph_string (struct glyph_string *s)
             || s->first_glyph->type == COMPOSITE_GLYPH))
     {
       n = ns_get_glyph_string_clip_rect (s, r);
-      ns_focus (s->f, r, n);
-      ns_maybe_dumpglyphs_background (s, 1);
-      ns_dumpglyphs_box_or_relief (s);
-      ns_unfocus (s->f);
+      if (ns_clip_to_rect (s->f, r, n))
+        {
+          ns_maybe_dumpglyphs_background (s, 1);
+          ns_dumpglyphs_box_or_relief (s);
+          ns_reset_clipping (s->f);
+        }
       box_drawn_p = 1;
     }
 
@@ -4101,9 +4080,11 @@ ns_draw_glyph_string (struct glyph_string *s)
 
     case IMAGE_GLYPH:
       n = ns_get_glyph_string_clip_rect (s, r);
-      ns_focus (s->f, r, n);
-      ns_dumpglyphs_image (s, r[0]);
-      ns_unfocus (s->f);
+      if (ns_clip_to_rect (s->f, r, n))
+        {
+          ns_dumpglyphs_image (s, r[0]);
+          ns_reset_clipping (s->f);
+        }
       break;
 
     case STRETCH_GLYPH:
@@ -4113,66 +4094,68 @@ ns_draw_glyph_string (struct glyph_string *s)
     case CHAR_GLYPH:
     case COMPOSITE_GLYPH:
       n = ns_get_glyph_string_clip_rect (s, r);
-      ns_focus (s->f, r, n);
+      if (ns_clip_to_rect (s->f, r, n))
+        {
+          if (s->for_overlaps || (s->cmp_from > 0
+                                  && ! s->first_glyph->u.cmp.automatic))
+            s->background_filled_p = 1;
+          else
+            ns_maybe_dumpglyphs_background
+              (s, s->first_glyph->type == COMPOSITE_GLYPH);
 
-      if (s->for_overlaps || (s->cmp_from > 0
-                              && ! s->first_glyph->u.cmp.automatic))
-        s->background_filled_p = 1;
-      else
-        ns_maybe_dumpglyphs_background
-          (s, s->first_glyph->type == COMPOSITE_GLYPH);
+          if (s->hl == DRAW_CURSOR && s->w->phys_cursor_type == FILLED_BOX_CURSOR)
+            {
+              unsigned long tmp = NS_FACE_BACKGROUND (s->face);
+              NS_FACE_BACKGROUND (s->face) = NS_FACE_FOREGROUND (s->face);
+              NS_FACE_FOREGROUND (s->face) = tmp;
+            }
 
-      if (s->hl == DRAW_CURSOR && s->w->phys_cursor_type == FILLED_BOX_CURSOR)
-        {
-          unsigned long tmp = NS_FACE_BACKGROUND (s->face);
-          NS_FACE_BACKGROUND (s->face) = NS_FACE_FOREGROUND (s->face);
-          NS_FACE_FOREGROUND (s->face) = tmp;
-        }
+          {
+            BOOL isComposite = s->first_glyph->type == COMPOSITE_GLYPH;
 
-      {
-        BOOL isComposite = s->first_glyph->type == COMPOSITE_GLYPH;
+            if (isComposite)
+              ns_draw_composite_glyph_string_foreground (s);
+            else
+              ns_draw_glyph_string_foreground (s);
+          }
 
-        if (isComposite)
-          ns_draw_composite_glyph_string_foreground (s);
-        else
-          ns_draw_glyph_string_foreground (s);
-      }
+          {
+            NSColor *col = (NS_FACE_FOREGROUND (s->face) != 0
+                            ? ns_lookup_indexed_color (NS_FACE_FOREGROUND (s->face),
+                                                       s->f)
+                            : FRAME_FOREGROUND_COLOR (s->f));
+            [col set];
+
+            /* Draw underline, overline, strike-through.  */
+            ns_draw_text_decoration (s, s->face, col, s->width, s->x);
+          }
 
-      {
-        NSColor *col = (NS_FACE_FOREGROUND (s->face) != 0
-                        ? ns_lookup_indexed_color (NS_FACE_FOREGROUND (s->face),
-                                                   s->f)
-                        : FRAME_FOREGROUND_COLOR (s->f));
-        [col set];
-
-        /* Draw underline, overline, strike-through. */
-        ns_draw_text_decoration (s, s->face, col, s->width, s->x);
-      }
+          if (s->hl == DRAW_CURSOR && s->w->phys_cursor_type == FILLED_BOX_CURSOR)
+            {
+              unsigned long tmp = NS_FACE_BACKGROUND (s->face);
+              NS_FACE_BACKGROUND (s->face) = NS_FACE_FOREGROUND (s->face);
+              NS_FACE_FOREGROUND (s->face) = tmp;
+            }
 
-      if (s->hl == DRAW_CURSOR && s->w->phys_cursor_type == FILLED_BOX_CURSOR)
-        {
-          unsigned long tmp = NS_FACE_BACKGROUND (s->face);
-          NS_FACE_BACKGROUND (s->face) = NS_FACE_FOREGROUND (s->face);
-          NS_FACE_FOREGROUND (s->face) = tmp;
+          ns_reset_clipping (s->f);
         }
-
-      ns_unfocus (s->f);
       break;
 
     case GLYPHLESS_GLYPH:
       n = ns_get_glyph_string_clip_rect (s, r);
-      ns_focus (s->f, r, n);
-
-      if (s->for_overlaps || (s->cmp_from > 0
-                              && ! s->first_glyph->u.cmp.automatic))
-        s->background_filled_p = 1;
-      else
-        ns_maybe_dumpglyphs_background
-          (s, s->first_glyph->type == COMPOSITE_GLYPH);
-      /* ... */
-      /* Not yet implemented.  */
-      /* ... */
-      ns_unfocus (s->f);
+      if (ns_clip_to_rect (s->f, r, n))
+        {
+          if (s->for_overlaps || (s->cmp_from > 0
+                                  && ! s->first_glyph->u.cmp.automatic))
+            s->background_filled_p = 1;
+          else
+            ns_maybe_dumpglyphs_background
+              (s, s->first_glyph->type == COMPOSITE_GLYPH);
+          /* ... */
+          /* Not yet implemented.  */
+          /* ... */
+          ns_reset_clipping (s->f);
+        }
       break;
 
     default:
@@ -4183,9 +4166,11 @@ ns_draw_glyph_string (struct glyph_string *s)
   if (!s->for_overlaps && !box_drawn_p && s->face->box != FACE_NO_BOX)
     {
       n = ns_get_glyph_string_clip_rect (s, r);
-      ns_focus (s->f, r, n);
-      ns_dumpglyphs_box_or_relief (s);
-      ns_unfocus (s->f);
+      if (ns_clip_to_rect (s->f, r, n))
+        {
+          ns_dumpglyphs_box_or_relief (s);
+          ns_reset_clipping (s->f);
+        }
     }
 
   s->num_clips = 0;
@@ -4991,7 +4976,7 @@ static struct redisplay_interface ns_redisplay_interface =
   ns_after_update_window_line,
   ns_update_window_begin,
   ns_update_window_end,
-  0, /* flush_display */
+  ns_flush_display, /* flush_display */
   x_clear_window_mouse_face,
   x_get_glyph_overhangs,
   x_fix_overlapping_area,