3 files changed, 20 insertions, 8 deletions

diff --git a/src/nsfns.m b/src/nsfns.m
index c8a41f5b4b0..81722681674 100644
--- a/src/nsfns.m
+++ b/src/nsfns.m
@@ -1234,6 +1234,10 @@ This function is an internal primitive--use `make-frame' instead.  */)
   x_default_parameter (f, parms, Qinternal_border_width, make_number (2),
                       "internalBorderWidth", "InternalBorderWidth",
                       RES_TYPE_NUMBER);
+  x_default_parameter (f, parms, Qright_divider_width, make_number (0),
+                       NULL, NULL, RES_TYPE_NUMBER);
+  x_default_parameter (f, parms, Qbottom_divider_width, make_number (0),
+                       NULL, NULL, RES_TYPE_NUMBER);
 
   /* default vertical scrollbars on right on Mac */
   {
diff --git a/src/w32term.c b/src/w32term.c
index e62d49dd947..7a3b2cc631f 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -660,21 +660,25 @@ w32_draw_window_divider (struct window *w, int x0, int x1, int y0, int y1)
                               ? face_last->foreground
                               : FRAME_FOREGROUND_PIXEL (f));
 
-  if (y1 - y0 > x1 - x0 && x1 - x0 > 2)
-    /* Vertical.  */
+  if ((y1 - y0 > x1 - x0) && (x1 - x0 >= 3))
+    /* A vertical divider, at least three pixels wide: Draw first and
+       last pixels differently.  */
     {
       w32_fill_area_abs (f, hdc, color_first, x0, y0, x0 + 1, y1);
       w32_fill_area_abs (f, hdc, color, x0 + 1, y0, x1 - 1, y1);
       w32_fill_area_abs (f, hdc, color_last, x1 - 1, y0, x1, y1);
     }
-  else if (x1 - x0 > y1 - y0 && y1 - y0 > 3)
-    /* Horizontal.  */
+  else if ((x1 - x0 > y1 - y0) && (y1 - y0 >= 3))
+    /* A horizontal divider, at least three pixels high: Draw first and
+       last pixels differently.  */
     {
       w32_fill_area_abs (f, hdc, color_first, x0, y0, x1, y0 + 1);
       w32_fill_area_abs (f, hdc, color, x0, y0 + 1, x1, y1 - 1);
       w32_fill_area_abs (f, hdc, color_last, x0, y1 - 1, x1, y1);
     }
   else
+    /* In any other case do not draw the first and last pixels
+       differently.  */
     w32_fill_area_abs (f, hdc, color, x0, y0, x1, y1);
 
   release_frame_dc (f, hdc);
diff --git a/src/xterm.c b/src/xterm.c
index 28abfaecde9..1deb7b46013 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -1104,8 +1104,9 @@ x_draw_window_divider (struct window *w, int x0, int x1, int y0, int y1)
                               : FRAME_FOREGROUND_PIXEL (f));
   Display *display = FRAME_X_DISPLAY (f);
 
-  if (y1 - y0 > x1 - x0 && x1 - x0 > 2)
-    /* Vertical.  */
+  if ((y1 - y0 > x1 - x0) && (x1 - x0 >= 3))
+    /* A vertical divider, at least three pixels wide: Draw first and
+       last pixels differently.  */
     {
       XSetForeground (display, f->output_data.x->normal_gc, color_first);
       x_fill_rectangle (f, f->output_data.x->normal_gc,
@@ -1117,8 +1118,9 @@ x_draw_window_divider (struct window *w, int x0, int x1, int y0, int y1)
       x_fill_rectangle (f, f->output_data.x->normal_gc,
                         x1 - 1, y0, 1, y1 - y0);
     }
-  else if (x1 - x0 > y1 - y0 && y1 - y0 > 3)
-    /* Horizontal.  */
+  else if ((x1 - x0 > y1 - y0) && (y1 - y0 >= 3))
+    /* A horizontal divider, at least three pixels high: Draw first and
+       last pixels differently.  */
     {
       XSetForeground (display, f->output_data.x->normal_gc, color_first);
       x_fill_rectangle (f, f->output_data.x->normal_gc,
@@ -1132,6 +1134,8 @@ x_draw_window_divider (struct window *w, int x0, int x1, int y0, int y1)
     }
   else
     {
+    /* In any other case do not draw the first and last pixels
+       differently.  */
       XSetForeground (display, f->output_data.x->normal_gc, color);
       x_fill_rectangle (f, f->output_data.x->normal_gc,
                         x0, y0, x1 - x0, y1 - y0);