Subject: Re: bug#31904: scatch/ns-drawing

From: Alan Third <[email-masked]>
Date: Sat, 18 Aug 2018 15:02:33 +0100

On Wed, Aug 15, 2018 at 04:54:26PM -0700, [email-masked] wrote:
> For what it’s worth, the scratch/ns-drawing branch has fixed this for me.
> 
>     https://github.com/emacs-mirror/emacs/tree/scratch/ns-drawing <https://github.com/emacs-mirror/emacs/tree/scratch/ns-drawing>

Thanks for the confirmation.

I think I’ll have to port it to Emacs 26. It’s quite a large change,
but if Emacs 26 in its current form simply doesn’t work at all with
the next release of macOS I don’t see that we have much choice.

Can you please try the attached patch against emacs-26?
-- 
Alan Third
>From 9e71b4aa4ece9ced6b888db403e9ae027501a625 Mon Sep 17 00:00:00 2001
From: Alan Third <[email-masked]>
Date: Sat, 4 Aug 2018 11:08:23 +0100
Subject: [PATCH] Force all NS drawing to be done from drawRect:

* 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.
(ns_unfocus): Don't unfocus the view any more.
(ns_clip_to_row): Update to match ns_focus.
(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.
---
 src/nsterm.m | 736 +++++++++++++++++++++++++--------------------------
 1 file changed, 365 insertions(+), 371 deletions(-)

diff --git a/src/nsterm.m b/src/nsterm.m
index 5ed71c9f8f..b36d847eb3 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -276,8 +276,6 @@ - (NSColor *)colorUsingDefaultColorSpace
 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?
@@ -1055,30 +1053,29 @@ static NSRect constrain_frame_rect(NSRect frameRect, bool isFullscreen)
   }
 #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.  */
+  /* FIXME: I don't think we need to do this.  */
 #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];
-      }
-  }
+  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
 
 #ifdef NS_IMPL_GNUSTEP
@@ -1164,23 +1161,14 @@ static NSRect constrain_frame_rect(NSRect frameRect, bool isFullscreen)
    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
+
+static BOOL
 ns_focus (struct frame *f, NSRect *r, int n)
 /* --------------------------------------------------------------------------
    Internal: Focus on given frame.  During small local updates this is used to
@@ -1192,48 +1180,38 @@ static NSRect constrain_frame_rect(NSRect frameRect, bool isFullscreen)
    -------------------------------------------------------------------------- */
 {
   NSTRACE_WHEN (NSTRACE_GROUP_FOCUS, "ns_focus");
-  if (r != NULL)
+  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
-   -------------------------------------------------------------------------- */
+/* Internal: Restore the previous graphics state, unsetting any
+   clipping areas.  */
 {
   NSTRACE_WHEN (NSTRACE_GROUP_FOCUS, "ns_unfocus");
 
@@ -1242,21 +1220,10 @@ static NSRect constrain_frame_rect(NSRect frameRect, bool isFullscreen)
       [[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 +1242,17 @@ static NSRect constrain_frame_rect(NSRect frameRect, bool isFullscreen)
   clip_rect.size.width = window_width;
   clip_rect.size.height = row->visible_height;
 
-  ns_focus (f, &clip_rect, 1);
+  return ns_focus (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_focus), then this will call
+   draw_rect: which will "expose" those areas.  */
+{
+  [FRAME_NS_VIEW (f) displayIfNeeded];
 }

@@ -2699,14 +2676,16 @@ so some key presses (TAB) are swallowed by the system. */
   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_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);
+    }
   unblock_input ();
 }
 
@@ -2727,13 +2706,14 @@ so some key presses (TAB) are swallowed by the system. */
   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_focus (f, &r, 1))
+    {
+      [ns_lookup_indexed_color (NS_FACE_BACKGROUND (face), f) set];
 
-  NSRectFill (r);
+      NSRectFill (r);
 
-  ns_unfocus (f);
-  return;
+      ns_unfocus (f);
+    }
 }
 
 static void
@@ -2745,11 +2725,11 @@ so some key presses (TAB) are swallowed by the system. */
     {
       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 +2940,86 @@ so some key presses (TAB) are swallowed by the system. */
     }
 
   /* 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);
-        }
-    }
-
-  if (p->which)
-    {
-      NSRect r = NSMakeRect (p->x, p->y, p->wd, p->h);
-      EmacsImage *img = bimgs[p->which - 1];
+          int bx = p->bx, by = p->by, nx = p->nx, ny = p->ny;
 
-      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_unfocus (f);
     }
-  ns_unfocus (f);
 }

@@ -3120,67 +3101,66 @@ Note that CURSOR_WIDTH is meaningful only for (h)bar cursors.
   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_unfocus() 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_unfocus (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 +3178,14 @@ Note that CURSOR_WIDTH is meaningful only for (h)bar cursors.
 
   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_focus (f, &r, 1))
+    {
+      if (face)
+        [ns_lookup_indexed_color(face->foreground, f) set];
 
-  NSRectFill(r);
-  ns_unfocus (f);
+      NSRectFill(r);
+      ns_unfocus (f);
+    }
 }

@@ -3230,39 +3212,40 @@ Note that CURSOR_WIDTH is meaningful only for (h)bar cursors.
 
   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.  */
-    {
-      [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.  */
+  if (ns_focus (f, &divider, 1))
     {
-      [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_unfocus (f);
+    }
 }
 
 static void
@@ -3846,83 +3829,84 @@ Function modeled after x_draw_glyph_string_box ().
       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_focus (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];
 
-              x = r[i].origin.x;
-              width = s->w->phys_cursor_width;
-              r[i].size.width -= width;
-              r[i].origin.x += width;
+              /* 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;
 
-              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_unfocus (s->f);
         }
-      ns_unfocus (s->f);
       s->background_filled_p = 1;
     }
 }
@@ -4072,9 +4056,11 @@ overwriting cursor (usually when cursor on a tab) */
             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_focus (s->f, r, n))
+                  {
+                    ns_maybe_dumpglyphs_background (s->next, 1);
+                    ns_unfocus (s->f);
+                  }
               }
             else
               {
@@ -4089,10 +4075,12 @@ overwriting cursor (usually when cursor on a tab) */
 	    || 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_focus (s->f, r, n))
+        {
+          ns_maybe_dumpglyphs_background (s, 1);
+          ns_dumpglyphs_box_or_relief (s);
+          ns_unfocus (s->f);
+        }
       box_drawn_p = 1;
     }
 
@@ -4101,9 +4089,11 @@ overwriting cursor (usually when cursor on a tab) */
 
     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_focus (s->f, r, n))
+        {
+          ns_dumpglyphs_image (s, r[0]);
+          ns_unfocus (s->f);
+        }
       break;
 
     case STRETCH_GLYPH:
@@ -4113,66 +4103,68 @@ overwriting cursor (usually when cursor on a tab) */
     case CHAR_GLYPH:
     case COMPOSITE_GLYPH:
       n = ns_get_glyph_string_clip_rect (s, r);
-      ns_focus (s->f, r, n);
+      if (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);
 
-      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_unfocus (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_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);
+        }
       break;
 
     default:
@@ -4183,9 +4175,11 @@ overwriting cursor (usually when cursor on a tab) */
   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_focus (s->f, r, n))
+        {
+          ns_dumpglyphs_box_or_relief (s);
+          ns_unfocus (s->f);
+        }
     }
 
   s->num_clips = 0;
@@ -4991,7 +4985,7 @@ static Lisp_Object ns_string_to_lispmod (const char *s)
   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,
-- 
2.17.1