Allow negative line width for :box face attribute

Separate values for box line width and height and allow both to be
negative which makes the visual width and height of the boxed string
unchanged (Bug#13011).

* doc/lispref/display.texi (Face Attributes): Modify :box attribute
description to reflect the new possibilities.
* lisp/cus-face.el (custom-face-attributes): Set box attribute to get
two integer to set vertical and horizontal width and modify pre-filter
to accept dotted list of two int as valid box attribute.
* src/dispextern.h (face): Use two int for box horizontal and vertical
line width.

* src/nsfont.m (nsfont_draw): Use new face attributes.
* src/nsterm.m (ns_draw_box, ns_draw_relief): Support separated
horizontal and vertical box line width.
(ns_dumpglyphs_box_or_relief, ns_maybe_dumpglyphs_background)
(ns_dumpglyphs_image, ns_draw_glyph_string_foreground)
(ns_draw_composite_glyph_string_foreground): Use new face attributes.

* src/w32term.c (w32_draw_box_rect, w32_draw_relief_rect): Support
separated horizontal and vertical box line width.
(x_draw_glyph_string_background, x_draw_glyph_string_foreground)
(x_draw_composite_glyph_string_foreground)
(x_draw_glyphless_glyph_string_foreground, x_draw_glyph_string_box)
(x_draw_image_foreground, x_draw_image_relief)
(w32_draw_image_foreground_1, x_draw_image_glyph_string): Use new face
attributes.

* src/xfaces.c (Sinternal_set_lisp_face_attribute, realize_x_face):
Accept box attribute as a list of two ints.

* src/xdisp.c (estimate_mode_line_height, produce_image_glyph)
(produce_xwidget_glyph, x_produce_glyphs): Use new face attributes.
* src/xterm.c (x_draw_box_rect, x_draw_relief_rect): Support separated
horizontal and vertical box line width.
(x_draw_glyph_string_background, x_draw_glyph_string_foreground)
(x_draw_composite_glyph_string_foreground)
(x_draw_glyphless_glyph_string_foreground, x_draw_glyph_string_box)
(x_draw_image_foreground, x_draw_image_relief, x_draw_image_foreground_1)
(x_draw_image_glyph_string): Use new face attributes.

7 files changed, 207 insertions, 202 deletions

diff --git a/src/dispextern.h b/src/dispextern.h
index 08380f1f17f..555946f84cb 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -1693,12 +1693,17 @@ struct face
   int fontset;
 
   /* Non-zero means characters in this face have a box of that
-     thickness around them.  If this value is negative, its absolute
-     value indicates the thickness, and the horizontal (top and
-     bottom) borders of box are drawn inside of the character glyphs'
-     area.  The vertical (left and right) borders of the box are drawn
-     in the same way as when this value is positive.  */
-  int box_line_width;
+     thickness around them. Vertical (left and right) and horizontal
+     (top and bottom) borders size can be set separatedly using an
+     associated list of two ints in the form
+     (vertical_size . horizontal_size). In case one of the value is
+     negative, its absolute value indicates the thickness, and the
+     borders of box are drawn inside of the character glyphs' area
+     potentially over the glyph itself but the glyph drawing size is
+     not increase. If a (signed) int N is use instead of a list, it
+     is the same as setting ( abs(N) . N ) values. */
+  int box_vertical_line_width;
+  int box_horizontal_line_width;
 
   /* Type of box drawn.  A value of FACE_NO_BOX means no box is drawn
      around text in this face.  A value of FACE_SIMPLE_BOX means a box
diff --git a/src/nsfont.m b/src/nsfont.m
index 9bec3691786..e41a698a2ff 100644
--- a/src/nsfont.m
+++ b/src/nsfont.m
@@ -1043,7 +1043,7 @@ nsfont_draw (struct glyph_string *s, int from, int to, int x, int y,
 
   r.origin.x = s->x;
   if (s->face->box != FACE_NO_BOX && s->first_glyph->left_box_line_p)
-    r.origin.x += abs (s->face->box_line_width);
+    r.origin.x += max (s->face->box_vertical_line_width, 0);
 
   r.origin.y = s->y;
   r.size.height = FONT_HEIGHT (font);
@@ -1105,7 +1105,7 @@ nsfont_draw (struct glyph_string *s, int from, int to, int x, int y,
     {
       NSRect br = r;
       int fibw = FRAME_INTERNAL_BORDER_WIDTH (s->f);
-      int mbox_line_width = max (s->face->box_line_width, 0);
+      int mbox_line_width = max (s->face->box_vertical_line_width, 0);
 
       if (s->row->full_width_p)
         {
@@ -1129,9 +1129,10 @@ nsfont_draw (struct glyph_string *s, int from, int to, int x, int y,
         }
       else
         {
-          int correction = abs (s->face->box_line_width)+1;
+          int correction = abs (s->face->box_horizontal_line_width)+1;
           br.origin.y += correction;
           br.size.height -= 2*correction;
+          correction = abs (s->face->box_vertical_line_width)+1;
           br.origin.x += correction;
           br.size.width -= 2*correction;
         }
diff --git a/src/nsterm.m b/src/nsterm.m
index 04fc0512234..3ce223307ba 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -3639,8 +3639,8 @@ ns_draw_text_decoration (struct glyph_string *s, struct face *face,
 }
 
 static void
-ns_draw_box (NSRect r, CGFloat thickness, NSColor *col,
-             char left_p, char right_p)
+ns_draw_box (NSRect r, CGFloat hthickness, CGFloat vthickness,
+             NSColor *col, char left_p, char right_p)
 /* --------------------------------------------------------------------------
     Draw an unfilled rect inside r, optionally leaving left and/or right open.
     Note we can't just use an NSDrawRect command, because of the possibility
@@ -3651,28 +3651,28 @@ ns_draw_box (NSRect r, CGFloat thickness, NSColor *col,
   [col set];
 
   /* top, bottom */
-  s.size.height = thickness;
+  s.size.height = hthickness;
   NSRectFill (s);
-  s.origin.y += r.size.height - thickness;
+  s.origin.y += r.size.height - hthickness;
   NSRectFill (s);
 
   s.size.height = r.size.height;
   s.origin.y = r.origin.y;
 
   /* left, right (optional) */
-  s.size.width = thickness;
+  s.size.width = vthickness;
   if (left_p)
     NSRectFill (s);
   if (right_p)
     {
-      s.origin.x += r.size.width - thickness;
+      s.origin.x += r.size.width - vthickness;
       NSRectFill (s);
     }
 }
 
 
 static void
-ns_draw_relief (NSRect r, int thickness, char raised_p,
+ns_draw_relief (NSRect r, int hthickness, int vthickness, char raised_p,
                char top_p, char bottom_p, char left_p, char right_p,
                struct glyph_string *s)
 /* --------------------------------------------------------------------------
@@ -3722,27 +3722,27 @@ ns_draw_relief (NSRect r, int thickness, char raised_p,
   /* TODO: mitering. Using NSBezierPath doesn't work because of color switch.  */
 
   /* top */
-  sr.size.height = thickness;
+  sr.size.height = hthickness;
   if (top_p) NSRectFill (sr);
 
   /* left */
   sr.size.height = r.size.height;
-  sr.size.width = thickness;
+  sr.size.width = vthickness;
   if (left_p) NSRectFill (sr);
 
   [(raised_p ? darkCol : lightCol) set];
 
   /* bottom */
   sr.size.width = r.size.width;
-  sr.size.height = thickness;
-  sr.origin.y += r.size.height - thickness;
+  sr.size.height = hthickness;
+  sr.origin.y += r.size.height - hthickness;
   if (bottom_p) NSRectFill (sr);
 
   /* right */
   sr.size.height = r.size.height;
   sr.origin.y = r.origin.y;
-  sr.size.width = thickness;
-  sr.origin.x += r.size.width - thickness;
+  sr.size.width = vthickness;
+  sr.origin.x += r.size.width - vthickness;
   if (right_p) NSRectFill (sr);
 }
 
@@ -3758,7 +3758,7 @@ ns_dumpglyphs_box_or_relief (struct glyph_string *s)
   char left_p, right_p;
   struct glyph *last_glyph;
   NSRect r;
-  int thickness;
+  int hthickness, vthickness;
   struct face *face;
 
   if (s->hl == DRAW_MOUSE_FACE)
@@ -3771,7 +3771,8 @@ ns_dumpglyphs_box_or_relief (struct glyph_string *s)
   else
     face = s->face;
 
-  thickness = face->box_line_width;
+  vthickness = face->box_vertical_line_width;
+  hthickness = face->box_horizontal_line_width;
 
   NSTRACE ("ns_dumpglyphs_box_or_relief");
 
@@ -3796,14 +3797,15 @@ ns_dumpglyphs_box_or_relief (struct glyph_string *s)
   /* TODO: Sometimes box_color is 0 and this seems wrong; should investigate.  */
   if (s->face->box == FACE_SIMPLE_BOX && s->face->box_color)
     {
-      ns_draw_box (r, abs (thickness),
+      ns_draw_box (r, abs (hthickness), abs (vthickness),
                    ns_lookup_indexed_color (face->box_color, s->f),
-                  left_p, right_p);
+                   left_p, right_p);
     }
   else
     {
-      ns_draw_relief (r, abs (thickness), s->face->box == FACE_RAISED_BOX,
-                     1, 1, left_p, right_p, s);
+      ns_draw_relief (r, abs (hthickness), abs (vthickness),
+                      s->face->box == FACE_RAISED_BOX,
+                      1, 1, left_p, right_p, s);
     }
 }
 
@@ -3819,7 +3821,7 @@ ns_maybe_dumpglyphs_background (struct glyph_string *s, char force_p)
 
   if (!s->background_filled_p/* || s->hl == DRAW_MOUSE_FACE*/)
     {
-      int box_line_width = max (s->face->box_line_width, 0);
+      int box_line_width = max (s->face->box_horizontal_line_width, 0);
       if (FONT_HEIGHT (s->font) < s->height - 2 * box_line_width
           /* When xdisp.c ignores FONT_HEIGHT, we cannot trust font
              dimensions, since the actual glyphs might be much
@@ -3870,7 +3872,7 @@ ns_dumpglyphs_image (struct glyph_string *s, NSRect r)
    -------------------------------------------------------------------------- */
 {
   EmacsImage *img = s->img->pixmap;
-  int box_line_vwidth = max (s->face->box_line_width, 0);
+  int box_line_vwidth = max (s->face->box_horizontal_line_width, 0);
   int x = s->x, y = s->ybase - image_ascent (s->img, s->face, &s->slice);
   int bg_x, bg_y, bg_height;
   int th;
@@ -3883,7 +3885,7 @@ ns_dumpglyphs_image (struct glyph_string *s, NSRect r)
 
   if (s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p && s->slice.x == 0)
-    x += abs (s->face->box_line_width);
+    x += max (s->face->box_vertical_line_width, 0);
 
   bg_x = x;
   bg_y =  s->slice.y == 0 ? s->y : s->y + box_line_vwidth;
@@ -4003,7 +4005,7 @@ ns_dumpglyphs_image (struct glyph_string *s, NSRect r)
       r.origin.y = y - th;
       r.size.width = s->slice.width + 2*th-1;
       r.size.height = s->slice.height + 2*th-1;
-      ns_draw_relief (r, th, raised_p,
+      ns_draw_relief (r, th, th, raised_p,
                       s->slice.y == 0,
                       s->slice.y + s->slice.height == s->img->height,
                       s->slice.x == 0,
@@ -4017,7 +4019,7 @@ ns_dumpglyphs_image (struct glyph_string *s, NSRect r)
     {
       int thickness = abs (s->img->relief);
       if (thickness == 0) thickness = 1;
-      ns_draw_box (br, thickness, FRAME_CURSOR_COLOR (s->f), 1, 1);
+      ns_draw_box (br, thickness, thickness, FRAME_CURSOR_COLOR (s->f), 1, 1);
     }
 }
 
@@ -4100,7 +4102,7 @@ ns_draw_glyph_string_foreground (struct glyph_string *s)
      of S to the right of that box line.  */
   if (s->face && s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p)
-    x = s->x + eabs (s->face->box_line_width);
+    x = s->x + max (s->face->box_vertical_line_width, 0);
   else
     x = s->x;
 
@@ -4126,7 +4128,7 @@ ns_draw_composite_glyph_string_foreground (struct glyph_string *s)
      of S to the right of that box line.  */
   if (s->face && s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p)
-    x = s->x + eabs (s->face->box_line_width);
+    x = s->x + max (s->face->box_vertical_line_width, 0);
   else
     x = s->x;
 
@@ -4142,7 +4144,7 @@ ns_draw_composite_glyph_string_foreground (struct glyph_string *s)
       if (s->cmp_from == 0)
         {
           NSRect r = NSMakeRect (s->x, s->y, s->width-1, s->height -1);
-          ns_draw_box (r, 1, FRAME_CURSOR_COLOR (s->f), 1, 1);
+          ns_draw_box (r, 1, 1, FRAME_CURSOR_COLOR (s->f), 1, 1);
         }
     }
   else if (! s->first_glyph->u.cmp.automatic)
diff --git a/src/w32term.c b/src/w32term.c
index 76cf6bd6964..5fa77d58e10 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -888,10 +888,10 @@ static void w32_draw_image_foreground_1 (struct glyph_string *, HBITMAP);
 static void w32_clear_glyph_string_rect (struct glyph_string *, int,
                                          int, int, int);
 static void w32_draw_relief_rect (struct frame *, int, int, int, int,
-                                  int, int, int, int, int, int,
+                                  int, int, int, int, int, int, int,
                                   RECT *);
 static void w32_draw_box_rect (struct glyph_string *, int, int, int, int,
-                               int, bool, bool, RECT *);
+                               int, int, bool, bool, RECT *);
 
 
 /* Set S->gc to a suitable GC for drawing glyph string S in cursor
@@ -1160,7 +1160,7 @@ w32_draw_glyph_string_background (struct glyph_string *s, bool force_p)
      shouldn't be drawn in the first place.  */
   if (!s->background_filled_p)
     {
-      int box_line_width = max (s->face->box_line_width, 0);
+      int box_line_width = max (s->face->box_horizontal_line_width, 0);
 
 #if 0 /* TODO: stipple */
       if (s->stippled_p)
@@ -1206,7 +1206,7 @@ w32_draw_glyph_string_foreground (struct glyph_string *s)
      of S to the right of that box line.  */
   if (s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p)
-    x = s->x + eabs (s->face->box_line_width);
+    x = s->x + max (s->face->box_vertical_line_width, 0);
   else
     x = s->x;
 
@@ -1264,7 +1264,7 @@ w32_draw_composite_glyph_string_foreground (struct glyph_string *s)
      of S to the right of that box line.  */
   if (s->face && s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p)
-    x = s->x + eabs (s->face->box_line_width);
+    x = s->x + max (s->face->box_vertical_line_width, 0);
   else
     x = s->x;
 
@@ -1361,7 +1361,7 @@ w32_draw_glyphless_glyph_string_foreground (struct glyph_string *s)
      of S to the right of that box line.  */
   if (s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p)
-    x = s->x + eabs (s->face->box_line_width);
+    x = s->x + max (s->face->box_vertical_line_width, 0);
   else
     x = s->x;
 
@@ -1617,7 +1617,7 @@ w32_setup_relief_colors (struct glyph_string *s)
 static void
 w32_draw_relief_rect (struct frame *f,
                       int left_x, int top_y, int right_x, int bottom_y,
-                      int width, int raised_p,
+                      int hwidth, int vwidth, int raised_p,
                       int top_p, int bot_p, int left_p, int right_p,
                       RECT *clip_rect)
 {
@@ -1634,14 +1634,14 @@ w32_draw_relief_rect (struct frame *f,
 
   /* Top.  */
   if (top_p)
-    for (i = 0; i < width; ++i)
+    for (i = 0; i < hwidth; ++i)
       w32_fill_area (f, hdc, gc.foreground,
                      left_x + i * left_p, top_y + i,
                      right_x - left_x - i * (left_p + right_p ) + 1, 1);
 
   /* Left.  */
   if (left_p)
-    for (i = 0; i < width; ++i)
+    for (i = 0; i < vwidth; ++i)
       w32_fill_area (f, hdc, gc.foreground,
                      left_x + i, top_y + (i + 1) * top_p, 1,
                      bottom_y - top_y - (i + 1) * (bot_p + top_p) + 1);
@@ -1653,14 +1653,14 @@ w32_draw_relief_rect (struct frame *f,
 
   /* Bottom.  */
   if (bot_p)
-    for (i = 0; i < width; ++i)
+    for (i = 0; i < hwidth; ++i)
       w32_fill_area (f, hdc, gc.foreground,
                      left_x + i * left_p, bottom_y - i,
                      right_x - left_x - i * (left_p + right_p) + 1, 1);
 
   /* Right.  */
   if (right_p)
-    for (i = 0; i < width; ++i)
+    for (i = 0; i < vwidth; ++i)
       w32_fill_area (f, hdc, gc.foreground,
                      right_x - i, top_y + (i + 1) * top_p, 1,
                      bottom_y - top_y - (i + 1) * (bot_p + top_p) + 1);
@@ -1680,31 +1680,31 @@ w32_draw_relief_rect (struct frame *f,
 
 static void
 w32_draw_box_rect (struct glyph_string *s,
-                   int left_x, int top_y, int right_x, int bottom_y, int width,
-                   bool left_p, bool right_p, RECT *clip_rect)
+                   int left_x, int top_y, int right_x, int bottom_y, int hwidth,
+                   int vwidth, bool left_p, bool right_p, RECT *clip_rect)
 {
   w32_set_clip_rectangle (s->hdc, clip_rect);
 
   /* Top.  */
   w32_fill_area (s->f, s->hdc, s->face->box_color,
-                  left_x, top_y, right_x - left_x + 1, width);
+                  left_x, top_y, right_x - left_x + 1, hwidth);
 
   /* Left.  */
   if (left_p)
     {
       w32_fill_area (s->f, s->hdc, s->face->box_color,
-                     left_x, top_y, width, bottom_y - top_y + 1);
+                     left_x, top_y, vwidth, bottom_y - top_y + 1);
     }
 
   /* Bottom.  */
   w32_fill_area (s->f, s->hdc, s->face->box_color,
-                 left_x, bottom_y - width + 1, right_x - left_x + 1, width);
+                 left_x, bottom_y - hwidth + 1, right_x - left_x + 1, hwidth);
 
   /* Right.  */
   if (right_p)
     {
       w32_fill_area (s->f, s->hdc, s->face->box_color,
-                     right_x - width + 1, top_y, width, bottom_y - top_y + 1);
+                     right_x - vwidth + 1, top_y, vwidth, bottom_y - top_y + 1);
     }
 
   w32_set_clip_rectangle (s->hdc, NULL);
@@ -1716,7 +1716,7 @@ w32_draw_box_rect (struct glyph_string *s,
 static void
 w32_draw_glyph_string_box (struct glyph_string *s)
 {
-  int width, left_x, right_x, top_y, bottom_y, last_x;
+  int hwidth, vwidth, left_x, right_x, top_y, bottom_y, last_x;
   bool left_p, right_p, raised_p;
   struct glyph *last_glyph;
   RECT clip_rect;
@@ -1730,7 +1730,8 @@ w32_draw_glyph_string_box (struct glyph_string *s)
                 ? s->first_glyph
                 : s->first_glyph + s->nchars - 1);
 
-  width = eabs (s->face->box_line_width);
+  vwidth = eabs (s->face->box_vertical_line_width);
+  hwidth = eabs (s->face->box_horizontal_line_width);
   raised_p = s->face->box == FACE_RAISED_BOX;
   left_x = s->x;
   right_x = ((s->row->full_width_p && s->extends_to_end_of_line_p
@@ -1751,13 +1752,13 @@ w32_draw_glyph_string_box (struct glyph_string *s)
   get_glyph_string_clip_rect (s, &clip_rect);
 
   if (s->face->box == FACE_SIMPLE_BOX)
-    w32_draw_box_rect (s, left_x, top_y, right_x, bottom_y, width,
-                       left_p, right_p, &clip_rect);
+    w32_draw_box_rect (s, left_x, top_y, right_x, bottom_y, hwidth,
+                       vwidth, left_p, right_p, &clip_rect);
   else
     {
       w32_setup_relief_colors (s);
-      w32_draw_relief_rect (s->f, left_x, top_y, right_x, bottom_y,
-                            width, raised_p, 1, 1, left_p, right_p, &clip_rect);
+      w32_draw_relief_rect (s->f, left_x, top_y, right_x, bottom_y, hwidth,
+                            vwidth, raised_p, 1, 1, left_p, right_p, &clip_rect);
     }
 }
 
@@ -1795,7 +1796,7 @@ w32_draw_image_foreground (struct glyph_string *s)
   if (s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p
       && s->slice.x == 0)
-    x += eabs (s->face->box_line_width);
+    x += max (s->face->box_vertical_line_width, 0);
 
   /* If there is a margin around the image, adjust x- and y-position
      by that margin.  */
@@ -1982,7 +1983,7 @@ w32_draw_image_relief (struct glyph_string *s)
   if (s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p
       && s->slice.x == 0)
-    x += eabs (s->face->box_line_width);
+    x += max (s->face->box_vertical_line_width, 0);
 
   /* If there is a margin around the image, adjust x- and y-position
      by that margin.  */
@@ -2034,7 +2035,7 @@ w32_draw_image_relief (struct glyph_string *s)
 
   w32_setup_relief_colors (s);
   get_glyph_string_clip_rect (s, &r);
-  w32_draw_relief_rect (s->f, x, y, x1, y1, thick, raised_p,
+  w32_draw_relief_rect (s->f, x, y, x1, y1, thick, thick, raised_p,
                         top_p, bot_p, left_p, right_p, &r);
 }
 
@@ -2054,7 +2055,7 @@ w32_draw_image_foreground_1 (struct glyph_string *s, HBITMAP pixmap)
   if (s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p
       && s->slice.x == 0)
-    x += eabs (s->face->box_line_width);
+    x += max (s->face->box_vertical_line_width, 0);
 
   /* If there is a margin around the image, adjust x- and y-position
      by that margin.  */
@@ -2167,8 +2168,8 @@ static void
 w32_draw_image_glyph_string (struct glyph_string *s)
 {
   int x, y;
-  int box_line_hwidth = eabs (s->face->box_line_width);
-  int box_line_vwidth = max (s->face->box_line_width, 0);
+  int box_line_hwidth = max (s->face->box_vertical_line_width, 0);
+  int box_line_vwidth = max (s->face->box_horizontal_line_width, 0);
   int height, width;
   HBITMAP pixmap = 0;
 
diff --git a/src/xdisp.c b/src/xdisp.c
index 61c798c59e8..cbdef7ad118 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -2061,8 +2061,8 @@ estimate_mode_line_height (struct frame *f, enum face_id face_id)
             {
               if (face->font)
                 height = normal_char_height (face->font, -1);
-              if (face->box_line_width > 0)
-                height += 2 * face->box_line_width;
+              if (face->box_horizontal_line_width > 0)
+                height += 2 * face->box_horizontal_line_width;
             }
         }
 
@@ -28900,18 +28900,21 @@ produce_image_glyph (struct it *it)
 
   if (face->box != FACE_NO_BOX)
     {
-      if (face->box_line_width > 0)
+      if (face->box_horizontal_line_width > 0)
         {
           if (slice.y == 0)
-            it->ascent += face->box_line_width;
+            it->ascent += face->box_horizontal_line_width;
           if (slice.y + slice.height == img->height)
-            it->descent += face->box_line_width;
+            it->descent += face->box_horizontal_line_width;
         }
 
-      if (it->start_of_box_run_p && slice.x == 0)
-        it->pixel_width += eabs (face->box_line_width);
-      if (it->end_of_box_run_p && slice.x + slice.width == img->width)
-        it->pixel_width += eabs (face->box_line_width);
+      if (face->box_vertical_line_width > 0)
+        {
+          if (it->start_of_box_run_p && slice.x == 0)
+            it->pixel_width += face->box_vertical_line_width;
+          if (it->end_of_box_run_p && slice.x + slice.width == img->width)
+            it->pixel_width += face->box_vertical_line_width;
+        }
     }
 
   take_vertical_position_into_account (it);
@@ -29009,15 +29012,18 @@ produce_xwidget_glyph (struct it *it)
 
   if (face->box != FACE_NO_BOX)
     {
-      if (face->box_line_width > 0)
+      if (face->box_horizontal_line_width > 0)
         {
-          it->ascent += face->box_line_width;
-          it->descent += face->box_line_width;
+          it->ascent += face->box_horizontal_line_width;
+          it->descent += face->box_horizontal_line_width;
         }
 
-      if (it->start_of_box_run_p)
-        it->pixel_width += eabs (face->box_line_width);
-      it->pixel_width += eabs (face->box_line_width);
+      if (face->box_vertical_line_width > 0)
+        {
+          if (it->start_of_box_run_p)
+            it->pixel_width += face->box_vertical_line_width;
+          it->pixel_width += face->box_vertical_line_width;
+        }
     }
 
   take_vertical_position_into_account (it);
@@ -29780,6 +29786,31 @@ produce_glyphless_glyph (struct it *it, bool for_no_font, Lisp_Object acronym)
 }
 
 
+/* If face has a box, add the box thickness to the character
+   height.  If character has a box line to the left and/or
+   right, add the box line width to the character's width.  */
+#define IT_APPLY_FACE_BOX(it, face)                             \
+  do {                                                          \
+    if (face->box != FACE_NO_BOX)                               \
+      {                                                         \
+        int thick = face->box_horizontal_line_width;            \
+        if (thick > 0)                                          \
+          {                                                     \
+            it->ascent += thick;                                \
+            it->descent += thick;                               \
+          }                                                     \
+                                                                \
+        thick = face->box_vertical_line_width;                  \
+        if (thick > 0)                                          \
+          {                                                     \
+            if (it->start_of_box_run_p)                         \
+              it->pixel_width += thick;                         \
+            if (it->end_of_box_run_p)                           \
+              it->pixel_width += thick;                         \
+          }                                                     \
+      }                                                         \
+    } while (false)
+
 /* RIF:
    Produce glyphs/get display metrics for the display element IT is
    loaded with.  See the description of struct it in dispextern.h
@@ -29895,26 +29926,7 @@ gui_produce_glyphs (struct it *it)
           if (stretched_p)
             it->pixel_width *= XFLOATINT (it->space_width);
 
-          /* If face has a box, add the box thickness to the character
-             height.  If character has a box line to the left and/or
-             right, add the box line width to the character's width.  */
-          if (face->box != FACE_NO_BOX)
-            {
-              int thick = face->box_line_width;
-
-              if (thick > 0)
-                {
-                  it->ascent += thick;
-                  it->descent += thick;
-                }
-              else
-                thick = -thick;
-
-              if (it->start_of_box_run_p)
-                it->pixel_width += thick;
-              if (it->end_of_box_run_p)
-                it->pixel_width += thick;
-            }
+          IT_APPLY_FACE_BOX(it, face);
 
           /* If face has an overline, add the height of the overline
              (1 pixel) and a 1 pixel margin to the character height.  */
@@ -30029,10 +30041,10 @@ gui_produce_glyphs (struct it *it)
 
               if ((it->max_ascent > 0 || it->max_descent > 0)
                   && face->box != FACE_NO_BOX
-                  && face->box_line_width > 0)
+                  && face->box_horizontal_line_width > 0)
                 {
-                  it->ascent += face->box_line_width;
-                  it->descent += face->box_line_width;
+                  it->ascent += face->box_horizontal_line_width;
+                  it->descent += face->box_horizontal_line_width;
                 }
               if (!NILP (height)
                   && XFIXNUM (height) > it->ascent + it->descent)
@@ -30439,23 +30451,7 @@ gui_produce_glyphs (struct it *it)
       it->pixel_width = cmp->pixel_width;
       it->ascent = it->phys_ascent = cmp->ascent;
       it->descent = it->phys_descent = cmp->descent;
-      if (face->box != FACE_NO_BOX)
-        {
-          int thick = face->box_line_width;
-
-          if (thick > 0)
-            {
-              it->ascent += thick;
-              it->descent += thick;
-            }
-          else
-            thick = - thick;
-
-          if (it->start_of_box_run_p)
-            it->pixel_width += thick;
-          if (it->end_of_box_run_p)
-            it->pixel_width += thick;
-        }
+      IT_APPLY_FACE_BOX(it, face);
 
       /* If face has an overline, add the height of the overline
          (1 pixel) and a 1 pixel margin to the character height.  */
@@ -30489,23 +30485,8 @@ gui_produce_glyphs (struct it *it)
         it->glyph_row->contains_overlapping_glyphs_p = true;
       it->ascent = it->phys_ascent = metrics.ascent;
       it->descent = it->phys_descent = metrics.descent;
-      if (face->box != FACE_NO_BOX)
-        {
-          int thick = face->box_line_width;
+      IT_APPLY_FACE_BOX(it, face);
 
-          if (thick > 0)
-            {
-              it->ascent += thick;
-              it->descent += thick;
-            }
-          else
-            thick = - thick;
-
-          if (it->start_of_box_run_p)
-            it->pixel_width += thick;
-          if (it->end_of_box_run_p)
-            it->pixel_width += thick;
-        }
       /* If face has an overline, add the height of the overline
          (1 pixel) and a 1 pixel margin to the character height.  */
       if (face->overline_p)
diff --git a/src/xfaces.c b/src/xfaces.c
index 711ec48bbdd..bab142ade0f 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -3128,6 +3128,8 @@ FRAME 0 means change the face on all frames, and change the default
         valid_p = XFIXNUM (value) != 0;
       else if (STRINGP (value))
         valid_p = SCHARS (value) > 0;
+      else if (CONSP (value) && FIXNUMP (XCAR (value)) && FIXNUMP (XCDR (value)))
+        valid_p = true;
       else if (CONSP (value))
         {
           Lisp_Object tem;
@@ -3146,7 +3148,9 @@ FRAME 0 means change the face on all frames, and change the default
 
               if (EQ (k, QCline_width))
                 {
-                  if (!FIXNUMP (v) || XFIXNUM (v) == 0)
+                  if ((!CONSP(v) || !FIXNUMP (XCAR (v)) || XFIXNUM (XCAR (v)) == 0
+                                 || !FIXNUMP (XCDR (v)) || XFIXNUM (XCDR (v)) == 0)
+                      && (!FIXNUMP (v) || XFIXNUM (v) == 0))
                     break;
                 }
               else if (EQ (k, QCcolor))
@@ -5815,7 +5819,7 @@ realize_gui_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE]
       face->box_color = load_color (f, face, attrs[LFACE_BOX_INDEX],
                                     LFACE_BOX_INDEX);
       face->box = FACE_SIMPLE_BOX;
-      face->box_line_width = 1;
+      face->box_vertical_line_width = face->box_horizontal_line_width = 1;
     }
   else if (FIXNUMP (box))
     {
@@ -5823,9 +5827,19 @@ realize_gui_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE]
          face.  */
       eassert (XFIXNUM (box) != 0);
       face->box = FACE_SIMPLE_BOX;
-      face->box_line_width = XFIXNUM (box);
+      face->box_vertical_line_width = eabs(XFIXNUM (box));
+      face->box_horizontal_line_width = XFIXNUM (box);
+      face->box_color = face->foreground;
+      face->box_color_defaulted_p = true;
+    }
+  else if (CONSP (box) && FIXNUMP (XCAR (box)) && FIXNUMP (XCDR (box)))
+    {
+        /* `(VWIDTH . HWIDTH)'.  */
+      face->box = FACE_SIMPLE_BOX;
       face->box_color = face->foreground;
       face->box_color_defaulted_p = true;
+      face->box_vertical_line_width = XFIXNUM (XCAR (box));
+      face->box_horizontal_line_width = XFIXNUM (XCDR (box));
     }
   else if (CONSP (box))
     {
@@ -5834,7 +5848,7 @@ realize_gui_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE]
       face->box = FACE_SIMPLE_BOX;
       face->box_color = face->foreground;
       face->box_color_defaulted_p = true;
-      face->box_line_width = 1;
+      face->box_vertical_line_width = face->box_horizontal_line_width = 1;
 
       while (CONSP (box))
         {
@@ -5850,8 +5864,14 @@ realize_gui_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE]
 
           if (EQ (keyword, QCline_width))
             {
-              if (FIXNUMP (value) && XFIXNUM (value) != 0)
-                face->box_line_width = XFIXNUM (value);
+              if (CONSP (value) && FIXNUMP (XCAR (value)) && FIXNUMP (XCDR (value))) {
+                  face->box_vertical_line_width = XFIXNUM (XCAR (value));
+                  face->box_horizontal_line_width = XFIXNUM (XCDR (value));
+              }
+              else if (FIXNUMP (value) && XFIXNUM (value) != 0) {
+                face->box_vertical_line_width = eabs (XFIXNUM (value));
+                face->box_horizontal_line_width = XFIXNUM (value);
+              }
             }
           else if (EQ (keyword, QCcolor))
             {
diff --git a/src/xterm.c b/src/xterm.c
index d7d992c91b2..fc68c77048f 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -1754,7 +1754,7 @@ x_draw_glyph_string_background (struct glyph_string *s, bool force_p)
      shouldn't be drawn in the first place.  */
   if (!s->background_filled_p)
     {
-      int box_line_width = max (s->face->box_line_width, 0);
+      int box_line_width = max (s->face->box_horizontal_line_width, 0);
 
       if (s->stippled_p)
         {
@@ -1799,7 +1799,7 @@ x_draw_glyph_string_foreground (struct glyph_string *s)
      of S to the right of that box line.  */
   if (s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p)
-    x = s->x + eabs (s->face->box_line_width);
+    x = s->x + max (s->face->box_vertical_line_width, 0);
   else
     x = s->x;
 
@@ -1849,7 +1849,7 @@ x_draw_glyph_string_foreground (struct glyph_string *s)
           if (!(s->for_overlaps
                 || (s->background_filled_p && s->hl != DRAW_CURSOR)))
             {
-              int box_line_width = max (s->face->box_line_width, 0);
+              int box_line_width = max (s->face->box_horizontal_line_width, 0);
 
               if (s->stippled_p)
                 {
@@ -1893,7 +1893,7 @@ x_draw_composite_glyph_string_foreground (struct glyph_string *s)
      of S to the right of that box line.  */
   if (s->face && s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p)
-    x = s->x + eabs (s->face->box_line_width);
+    x = s->x + max (s->face->box_vertical_line_width, 0);
   else
     x = s->x;
 
@@ -2004,7 +2004,7 @@ x_draw_glyphless_glyph_string_foreground (struct glyph_string *s)
      of S to the right of that box line.  */
   if (s->face && s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p)
-    x = s->x + eabs (s->face->box_line_width);
+    x = s->x + max (s->face->box_vertical_line_width, 0);
   else
     x = s->x;
 
@@ -2769,7 +2769,7 @@ x_setup_relief_colors (struct glyph_string *s)
 static void
 x_draw_relief_rect (struct frame *f,
                     int left_x, int top_y, int right_x, int bottom_y,
-                    int width, bool raised_p, bool top_p, bool bot_p,
+                    int hwidth, int vwidth, bool raised_p, bool top_p, bool bot_p,
                     bool left_p, bool right_p,
                     XRectangle *clip_rect)
 {
@@ -2794,7 +2794,7 @@ x_draw_relief_rect (struct frame *f,
   if (left_p)
     {
       x_fill_rectangle (f, top_left_gc, left_x, top_y,
-                        width, bottom_y + 1 - top_y);
+                        vwidth, bottom_y + 1 - top_y);
       if (top_p)
         corners |= 1 << CORNER_TOP_LEFT;
       if (bot_p)
@@ -2802,8 +2802,8 @@ x_draw_relief_rect (struct frame *f,
     }
   if (right_p)
     {
-      x_fill_rectangle (f, bottom_right_gc, right_x + 1 - width, top_y,
-                        width, bottom_y + 1 - top_y);
+      x_fill_rectangle (f, bottom_right_gc, right_x + 1 - vwidth, top_y,
+                        vwidth, bottom_y + 1 - top_y);
       if (top_p)
         corners |= 1 << CORNER_TOP_RIGHT;
       if (bot_p)
@@ -2813,25 +2813,25 @@ x_draw_relief_rect (struct frame *f,
     {
       if (!right_p)
         x_fill_rectangle (f, top_left_gc, left_x, top_y,
-                          right_x + 1 - left_x, width);
+                          right_x + 1 - left_x, hwidth);
       else
         x_fill_trapezoid_for_relief (f, top_left_gc, left_x, top_y,
-                                     right_x + 1 - left_x, width, 1);
+                                     right_x + 1 - left_x, hwidth, 1);
     }
   if (bot_p)
     {
       if (!left_p)
-        x_fill_rectangle (f, bottom_right_gc, left_x, bottom_y + 1 - width,
-                          right_x + 1 - left_x, width);
+        x_fill_rectangle (f, bottom_right_gc, left_x, bottom_y + 1 - hwidth,
+                          right_x + 1 - left_x, hwidth);
       else
         x_fill_trapezoid_for_relief (f, bottom_right_gc,
-                                     left_x, bottom_y + 1 - width,
-                                     right_x + 1 - left_x, width, 0);
+                                     left_x, bottom_y + 1 - hwidth,
+                                     right_x + 1 - left_x, hwidth, 0);
     }
-  if (left_p && width != 1)
+  if (left_p && vwidth > 1)
     x_fill_rectangle (f, bottom_right_gc, left_x, top_y,
                       1, bottom_y + 1 - top_y);
-  if (top_p && width != 1)
+  if (top_p && hwidth > 1)
     x_fill_rectangle (f, bottom_right_gc, left_x, top_y,
                       right_x + 1 - left_x, 1);
   if (corners)
@@ -2865,12 +2865,12 @@ x_draw_relief_rect (struct frame *f,
   /* Top.  */
   if (top_p)
     {
-      if (width == 1)
+      if (hwidth == 1)
         XDrawLine (dpy, drawable, gc,
                    left_x + left_p, top_y,
                    right_x + !right_p, top_y);
 
-      for (i = 1; i < width; ++i)
+      for (i = 1; i < hwidth; ++i)
         XDrawLine (dpy, drawable, gc,
                    left_x  + i * left_p, top_y + i,
                    right_x + 1 - i * right_p, top_y + i);
@@ -2879,13 +2879,10 @@ x_draw_relief_rect (struct frame *f,
   /* Left.  */
   if (left_p)
     {
-      if (width == 1)
+      if (vwidth == 1)
         XDrawLine (dpy, drawable, gc, left_x, top_y + 1, left_x, bottom_y);
 
-      x_clear_area(f, left_x, top_y, 1, 1);
-      x_clear_area(f, left_x, bottom_y, 1, 1);
-
-      for (i = (width > 1 ? 1 : 0); i < width; ++i)
+      for (i = 1; i < vwidth; ++i)
         XDrawLine (dpy, drawable, gc,
                    left_x + i, top_y + (i + 1) * top_p,
                    left_x + i, bottom_y + 1 - (i + 1) * bot_p);
@@ -2898,26 +2895,25 @@ x_draw_relief_rect (struct frame *f,
     gc = f->output_data.x->white_relief.gc;
   XSetClipRectangles (dpy, gc, 0, 0, clip_rect, 1, Unsorted);
 
-  if (width > 1)
-    {
-      /* Outermost top line.  */
-      if (top_p)
-        XDrawLine (dpy, drawable, gc,
-                   left_x  + left_p, top_y,
-                   right_x + !right_p, top_y);
+  /* Outermost top line.  */
+  if (top_p && hwidth > 1)
+    XDrawLine (dpy, drawable, gc,
+               left_x  + left_p, top_y,
+               right_x + !right_p, top_y);
 
-      /* Outermost left line.  */
-      if (left_p)
-        XDrawLine (dpy, drawable, gc, left_x, top_y + 1, left_x, bottom_y);
-    }
+  /* Outermost left line.  */
+  if (left_p && vwidth > 1)
+    XDrawLine (dpy, drawable, gc, left_x, top_y + 1, left_x, bottom_y);
 
   /* Bottom.  */
   if (bot_p)
     {
-      XDrawLine (dpy, drawable, gc,
-                 left_x + left_p, bottom_y,
-                 right_x + !right_p, bottom_y);
-      for (i = 1; i < width; ++i)
+      if (hwidth >= 1)
+        XDrawLine (dpy, drawable, gc,
+                   left_x + left_p, bottom_y,
+                   right_x + !right_p, bottom_y);
+
+      for (i = 1; i < hwidth; ++i)
         XDrawLine (dpy, drawable, gc,
                    left_x  + i * left_p, bottom_y - i,
                    right_x + 1 - i * right_p, bottom_y - i);
@@ -2926,9 +2922,7 @@ x_draw_relief_rect (struct frame *f,
   /* Right.  */
   if (right_p)
     {
-      x_clear_area(f, right_x, top_y, 1, 1);
-      x_clear_area(f, right_x, bottom_y, 1, 1);
-      for (i = 0; i < width; ++i)
+      for (i = 0; i < vwidth; ++i)
         XDrawLine (dpy, drawable, gc,
                    right_x - i, top_y + (i + 1) * top_p,
                    right_x - i, bottom_y + 1 - (i + 1) * bot_p);
@@ -2949,8 +2943,8 @@ x_draw_relief_rect (struct frame *f,
 
 static void
 x_draw_box_rect (struct glyph_string *s,
-                 int left_x, int top_y, int right_x, int bottom_y, int width,
-                 bool left_p, bool right_p, XRectangle *clip_rect)
+                 int left_x, int top_y, int right_x, int bottom_y, int hwidth,
+                 int vwidth, bool left_p, bool right_p, XRectangle *clip_rect)
 {
   Display *display = FRAME_X_DISPLAY (s->f);
   XGCValues xgcv;
@@ -2961,21 +2955,21 @@ x_draw_box_rect (struct glyph_string *s,
 
   /* Top.  */
   x_fill_rectangle (s->f, s->gc,
-                  left_x, top_y, right_x - left_x + 1, width);
+                  left_x, top_y, right_x - left_x + 1, hwidth);
 
   /* Left.  */
   if (left_p)
     x_fill_rectangle (s->f, s->gc,
-                    left_x, top_y, width, bottom_y - top_y + 1);
+                    left_x, top_y, vwidth, bottom_y - top_y + 1);
 
   /* Bottom.  */
   x_fill_rectangle (s->f, s->gc,
-                  left_x, bottom_y - width + 1, right_x - left_x + 1, width);
+                  left_x, bottom_y - hwidth + 1, right_x - left_x + 1, hwidth);
 
   /* Right.  */
   if (right_p)
     x_fill_rectangle (s->f, s->gc,
-                    right_x - width + 1, top_y, width, bottom_y - top_y + 1);
+                    right_x - vwidth + 1, top_y, vwidth, bottom_y - top_y + 1);
 
   XSetForeground (display, s->gc, xgcv.foreground);
   x_reset_clip_rectangles (s->f, s->gc);
@@ -2987,7 +2981,7 @@ x_draw_box_rect (struct glyph_string *s,
 static void
 x_draw_glyph_string_box (struct glyph_string *s)
 {
-  int width, left_x, right_x, top_y, bottom_y, last_x;
+  int hwidth, vwidth, left_x, right_x, top_y, bottom_y, last_x;
   bool raised_p, left_p, right_p;
   struct glyph *last_glyph;
   XRectangle clip_rect;
@@ -3001,7 +2995,8 @@ x_draw_glyph_string_box (struct glyph_string *s)
                 ? s->first_glyph
                 : s->first_glyph + s->nchars - 1);
 
-  width = eabs (s->face->box_line_width);
+  vwidth = eabs (s->face->box_vertical_line_width);
+  hwidth = eabs (s->face->box_horizontal_line_width);
   raised_p = s->face->box == FACE_RAISED_BOX;
   left_x = s->x;
   right_x = (s->row->full_width_p && s->extends_to_end_of_line_p
@@ -3022,13 +3017,13 @@ x_draw_glyph_string_box (struct glyph_string *s)
   get_glyph_string_clip_rect (s, &clip_rect);
 
   if (s->face->box == FACE_SIMPLE_BOX)
-    x_draw_box_rect (s, left_x, top_y, right_x, bottom_y, width,
-                     left_p, right_p, &clip_rect);
+    x_draw_box_rect (s, left_x, top_y, right_x, bottom_y, hwidth,
+                     vwidth, left_p, right_p, &clip_rect);
   else
     {
       x_setup_relief_colors (s);
-      x_draw_relief_rect (s->f, left_x, top_y, right_x, bottom_y,
-                          width, raised_p, true, true, left_p, right_p,
+      x_draw_relief_rect (s->f, left_x, top_y, right_x, bottom_y, hwidth,
+                          vwidth, raised_p, true, true, left_p, right_p,
                           &clip_rect);
     }
 }
@@ -3086,7 +3081,7 @@ x_draw_image_foreground (struct glyph_string *s)
   if (s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p
       && s->slice.x == 0)
-    x += eabs (s->face->box_line_width);
+    x += max (s->face->box_vertical_line_width, 0);
 
   /* If there is a margin around the image, adjust x- and y-position
      by that margin.  */
@@ -3205,7 +3200,7 @@ x_draw_image_relief (struct glyph_string *s)
   if (s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p
       && s->slice.x == 0)
-    x += eabs (s->face->box_line_width);
+    x += max (s->face->box_vertical_line_width, 0);
 
   /* If there is a margin around the image, adjust x- and y-position
      by that margin.  */
@@ -3273,7 +3268,7 @@ x_draw_image_relief (struct glyph_string *s)
 
   x_setup_relief_colors (s);
   get_glyph_string_clip_rect (s, &r);
-  x_draw_relief_rect (s->f, x, y, x1, y1, thick, raised_p,
+  x_draw_relief_rect (s->f, x, y, x1, y1, thick, thick, raised_p,
                       top_p, bot_p, left_p, right_p, &r);
 }
 
@@ -3292,7 +3287,7 @@ x_draw_image_foreground_1 (struct glyph_string *s, Pixmap pixmap)
   if (s->face->box != FACE_NO_BOX
       && s->first_glyph->left_box_line_p
       && s->slice.x == 0)
-    x += eabs (s->face->box_line_width);
+    x += max (s->face->box_vertical_line_width, 0);
 
   /* If there is a margin around the image, adjust x- and y-position
      by that margin.  */
@@ -3394,8 +3389,8 @@ x_draw_glyph_string_bg_rect (struct glyph_string *s, int x, int y, int w, int h)
 static void
 x_draw_image_glyph_string (struct glyph_string *s)
 {
-  int box_line_hwidth = eabs (s->face->box_line_width);
-  int box_line_vwidth = max (s->face->box_line_width, 0);
+  int box_line_hwidth = max (s->face->box_vertical_line_width, 0);
+  int box_line_vwidth = max (s->face->box_horizontal_line_width, 0);
   int height;
 #ifndef USE_CAIRO
   Display *display = FRAME_X_DISPLAY (s->f);