Re: [patch] add "underwave" face attribute

["Aurélien Aptel" <aurelien.aptel+emacs@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 765 bytes --]

On Sat, Feb 4, 2012 at 9:14 AM, Jan Djärv <jan.h.d@swipnet.se> wrote:
> Just create a new GC.

That's what I ended up doing, but the previous GC already sets a
clipping region that I override when underwaving. This results in
unneeded underwaving ie. visual glitches.

I've looked deeply at the code and found a function that returns a
simple clip rectangle of a glyph_string and used it with
x_intersect_rectangles() to have the final clipping region. I then use
the clip field of glyph_string to restore the previous clipping
rectangles.

I've done the same thing for Windows, it should work. Juanma, could
you check again, please?
Mac OSX clipping works differently and I'm not sure what to do... See
XXX coments in nsterm.m

Patch attached.

[-- Attachment #2: underwave-clip-1.patch --]
[-- Type: text/x-patch, Size: 33316 bytes --]

diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index 381eaf6..464dfaa 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -2080,10 +2080,32 @@ Background color, a string.  The value can be a system-defined color
 name, or a hexadecimal color specification.  @xref{Color Names}.
 
 @item :underline
-Whether or not characters should be underlined, and in what color.  If
-the value is @code{t}, underlining uses the foreground color of the
-face.  If the value is a string, underlining uses that color.  The
-value @code{nil} means do not underline.
+Whether or not characters should be underlined, and in what
+color. Here are the possible values of the @code{:underline}
+attribute, and what they mean:
+
+@table @asis
+@item @code{nil}
+Don't underline.
+
+@item @code{t}
+Underline with the foreground color of the face.
+
+@item @var{color}
+Underline in color @var{color}.
+
+@item @code{(:color @var{color} :style @var{style})}
+If @var{color} is a string, underline in it.
+If @var{color} is @code{foreground-color}, underline with the
+foreground color of the face.
+
+If @var{style} is @code{wave} underline with a wave.
+If @var{style} is @code{line} underline with a line. 
+
+If the attribute @code{:color} is omited, underline with the
+foreground color of the face.
+If the attribute @code{:style} is omited, underline with a line.
+@end table
 
 @item :overline
 Whether or not characters should be overlined, and in what color.
diff --git a/lisp/cus-face.el b/lisp/cus-face.el
index d725111..3680a26 100644
--- a/lisp/cus-face.el
+++ b/lisp/cus-face.el
@@ -135,8 +135,13 @@
      (choice :tag "Underline"
 	     :help-echo "Control text underlining."
 	     (const :tag "Off" nil)
-	     (const :tag "On" t)
-	     (color :tag "Colored")))
+	     (list :tag "On"
+		   (const :format "" :value :color)
+		   (choice :tag "Color" (const :tag "Foreground Color" foreground-color) color)
+                   (const :format "" :value :style)
+                   (choice :tag "Style"
+                           (const :tag "Line" line)
+                           (const :tag "Wave" wave)))))
 
     (:overline
      (choice :tag "Overline"
diff --git a/lisp/faces.el b/lisp/faces.el
index 5d406ad..e68abb1 100644
--- a/lisp/faces.el
+++ b/lisp/faces.el
@@ -616,10 +616,21 @@ VALUE must be a color name, a string.
 
 `:underline'
 
-VALUE specifies whether characters in FACE should be underlined.  If
-VALUE is t, underline with foreground color of the face.  If VALUE is
-a string, underline with that color.  If VALUE is nil, explicitly
-don't underline.
+VALUE specifies whether characters in FACE should be underlined.
+If VALUE is t, underline with foreground color of the face.
+If VALUE is a string, underline with that color.
+If VALUE is nil, explicitly don't underline.
+
+Otherwise, VALUE must be a property list of the form:
+
+`(:color COLOR :style STYLE)'.
+
+COLOR can be a either a color name string or `foreground-color'.
+STYLE can be either `line' or `wave'.
+If a keyword/value pair is missing from the property list, a
+default value will be used for the value.
+The default value of COLOR is the foreground color of the face.
+The default value of STYLE is `line'.
 
 `:overline'
 
diff --git a/src/dispextern.h b/src/dispextern.h
index 2c59f4f..cdbbc16 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -1510,6 +1510,13 @@ enum face_box_type
   FACE_SUNKEN_BOX
 };
 
+/* Underline type. */
+
+enum face_underline_type
+{
+  FACE_UNDER_LINE,
+  FACE_UNDER_WAVE
+};
 
 /* Structure describing a realized face.
 
@@ -1585,6 +1592,9 @@ struct face
      drawing shadows.  */
   unsigned use_box_color_for_shadows_p : 1;
 
+  /* Style of underlining. */
+  enum face_underline_type underline_type;
+
   /* Non-zero if text in this face should be underlined, overlined,
      strike-through or have a box drawn around it.  */
   unsigned underline_p : 1;
diff --git a/src/nsterm.m b/src/nsterm.m
index 70d3cc0..71c2f83 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -2596,6 +2596,86 @@ ns_get_glyph_string_clip_rect (struct glyph_string *s, NativeRectangle *nr)
   return n;
 }
 
+/* --------------------------------------------------------------------
+   Draw a wavy line under S. The wave fills wave_height pixels from y0.
+
+                    x0         wave_length = 2
+                                 --
+                y0   *   *   *   *   *
+                     |* * * * * * * * *
+    wave_height = 3  | *   *   *   *
+  --------------------------------------------------------------------- */
+
+static void
+ns_draw_underwave (int x0, int y0,
+                   int width,
+                   int wave_height, int wave_length)
+{
+  /* Helper macro to re-use NSPoint a and b to draw lines. */
+#define DRAWLINE(x1, y1, x2, y2)                        \
+  do                                                    \
+    {                                                   \
+      a.x = x1, a.y = y1;                               \
+      b.x = x2, b.y = y2;                               \
+      [NSBezierPath strokeLineFromPoint:a toPoint: b];  \
+    }                                                   \
+  while (0)
+
+  NSPoint a, b;
+  int wave_height = 2, wave_length = 3;
+  int dx, dy, x0, y0, width, x1, y1, x2, y2, odd, xmax;
+  XRectangle wave_clip, string_clip, final_clip;
+
+  dx = wave_length;
+  dy = wave_height - 1;
+  x0 = s->x;
+  y0 = s->ybase + 1;
+  width = s->width;
+  xmax = x0 + width;
+
+  /* Find and set clipping rectangle */
+
+  wave_clip = (XRectangle){ x0, y0, width, wave_height };
+  /* XXX: use ns_get_glyph_string_clip_rect() instead? */
+  get_glyph_string_clip_rect (s, &string_clip);
+
+  if (!x_intersect_rectangles (&wave_clip, &string_clip, &final_clip))
+    return;
+
+  /*
+     XXX: set clip rectangle
+     XSetClipRectangles (s->display, s->gc, 0, 0, &final_clip, 1, Unsorted);
+  */
+
+  /* Draw the waves */
+
+  x1 = x0 - (x0 % dx);
+  x2 = x1 + dx;
+  odd = (x1/dx) % 2;
+  y1 = y2 = y0;
+
+  if (odd)
+    y1 += dy;
+  else
+    y2 += dy;
+
+  while (x1 <= xmax)
+    {
+      DRAWLINE (x1, y1, x2, y2);
+      x1  = x2, y1 = y2;
+      x2 += dx, y2 = y0 + odd*dy;
+      odd = !odd;
+    }
+
+  /*
+    XXX: Restore previous clipping rectangle(s)
+    XSetClipRectangles (s->display, s->gc, 0, 0, s->clip, s->num_clips, Unsorted);
+  */
+#undef DRAWLINE
+}
+
+
+
 void
 ns_draw_text_decoration (struct glyph_string *s, struct face *face,
                          NSColor *defaultCol, CGFloat width, CGFloat x)
@@ -2609,63 +2689,77 @@ ns_draw_text_decoration (struct glyph_string *s, struct face *face,
   /* Do underline. */
   if (face->underline_p)
     {
-      NSRect r;
-      unsigned long thickness, position;
-
-      /* If the prev was underlined, match its appearance. */
-      if (s->prev && s->prev->face->underline_p
-          && s->prev->underline_thickness > 0)
+      if (s->face->underline_type == FACE_UNDER_WAVE)
         {
-          thickness = s->prev->underline_thickness;
-          position = s->prev->underline_position;
+          unsigned long height = 2, len = 3, y = s->ybase + 1;
+
+          if (face->underline_defaulted_p)
+            [defaultCol set];
+          else
+            [ns_lookup_indexed_color (face->underline_color, s->f) set];
+          
+          ns_draw_underwave (s->x, y, s->width, height, len);
         }
-      else
+      else if (s->face->underline_type == FACE_UNDER_LINE)
         {
-          struct font *font;
-          unsigned long descent;
-
-          font=s->font;
-          descent = s->y + s->height - s->ybase;
-
-          /* Use underline thickness of font, defaulting to 1. */
-          thickness = (font && font->underline_thickness > 0)
-            ? font->underline_thickness : 1;
-
-          /* Determine the offset of underlining from the baseline. */
-          if (x_underline_at_descent_line)
-            position = descent - thickness;
-          else if (x_use_underline_position_properties
-                   && font && font->underline_position >= 0)
-            position = font->underline_position;
-          else if (font)
-            position = lround (font->descent / 2);
-          else
-            position = underline_minimum_offset;
 
-          position = max (position, underline_minimum_offset);
+          NSRect r;
+          unsigned long thickness, position;
 
-          /* Ensure underlining is not cropped. */
-          if (descent <= position)
+          /* If the prev was underlined, match its appearance. */
+          if (s->prev && s->prev->face->underline_p
+              && s->prev->underline_thickness > 0)
             {
-              position = descent - 1;
-              thickness = 1;
+              thickness = s->prev->underline_thickness;
+              position = s->prev->underline_position;
             }
-          else if (descent < position + thickness)
-            thickness = 1;
-        }
+          else
+            {
+              struct font *font;
+              unsigned long descent;
+
+              font=s->font;
+              descent = s->y + s->height - s->ybase;
+
+              /* Use underline thickness of font, defaulting to 1. */
+              thickness = (font && font->underline_thickness > 0)
+                ? font->underline_thickness : 1;
+
+              /* Determine the offset of underlining from the baseline. */
+              if (x_underline_at_descent_line)
+                position = descent - thickness;
+              else if (x_use_underline_position_properties
+                       && font && font->underline_position >= 0)
+                position = font->underline_position;
+              else if (font)
+                position = lround (font->descent / 2);
+              else
+                position = underline_minimum_offset;
 
-      s->underline_thickness = thickness;
-      s->underline_position = position;
+              position = max (position, underline_minimum_offset);
 
-      r = NSMakeRect (x, s->ybase + position, width, thickness);
+              /* Ensure underlining is not cropped. */
+              if (descent <= position)
+                {
+                  position = descent - 1;
+                  thickness = 1;
+                }
+              else if (descent < position + thickness)
+                thickness = 1;
+            }
 
-      if (face->underline_defaulted_p)
-        [defaultCol set];
-      else
-        [ns_lookup_indexed_color (face->underline_color, s->f) set];
-      NSRectFill (r);
-    }
+          s->underline_thickness = thickness;
+          s->underline_position = position;
 
+          r = NSMakeRect (x, s->ybase + position, width, thickness);
+
+          if (face->underline_defaulted_p)
+            [defaultCol set];
+          else
+            [ns_lookup_indexed_color (face->underline_color, s->f) set];
+          NSRectFill (r);
+        }
+    }
   /* Do overline. We follow other terms in using a thickness of 1
      and ignoring overline_margin. */
   if (face->overline_p)
diff --git a/src/w32term.c b/src/w32term.c
index f764ad9..ebaa8f5 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -309,6 +309,93 @@ w32_set_clip_rectangle (HDC hdc, RECT *rect)
     SelectClipRgn (hdc, NULL);
 }
 
+/* Restore clipping rectangle in S */
+static void
+w32_restore_glyph_string_clip (struct glyph_string *s)
+{
+  RECT *r = s->clip;
+  int n = s->num_clips;
+
+  if (n == 1)
+    w32_set_clip_rectangle (s->hdc, r);
+  else if (n > 1)
+    {
+      HRGN clip1 = CreateRectRgnIndirect (r);
+      HRGN clip2 = CreateRectRgnIndirect (r + 1);
+      if (CombineRgn (clip1, clip1, clip2, RGN_OR) != ERROR)
+        SelectClipRgn (s->hdc, clip1);
+      DeleteObject (clip1);
+      DeleteObject (clip2);
+    }
+}
+
+/*
+   Draw a wavy line under S. The wave fills wave_height pixels from y0.
+
+                    x0         wave_length = 2
+                                 --
+                y0   *   *   *   *   *
+                     |* * * * * * * * *
+    wave_height = 3  | *   *   *   *
+
+*/
+
+void
+w32_draw_underwave (struct glyph_string *s, COLORREF color)
+{
+  int wave_height = 2, wave_length = 3;
+  int dx, dy, x0, y0, width, x1, y1, x2, y2, odd, xmax;
+  XRectangle wave_clip, string_clip, final_clip;
+  RECT w32_final_clip;
+  HPEN hp, oldhp;
+
+  dx = wave_length;
+  dy = wave_height - 1;
+  x0 = s->x;
+  y0 = s->ybase + 1;
+  width = s->width;
+  xmax = x0 + width;
+
+  /* Find and set clipping rectangle */
+
+  wave_clip = (XRectangle){ x0, y0, width, wave_height };
+  get_glyph_string_clip_rect (s, &string_clip);
+
+  if (!x_intersect_rectangles (&wave_clip, &string_clip, &final_clip))
+    return;
+
+  hp = CreatePen (PS_SOLID, 0, color);
+  oldhp = SelectObject (s->hdc, hp);
+  CONVERT_FROM_XRECT (final_clip, w32_final_clip);
+  w32_set_clip_rectangle (w32_final_clip);
+
+  /* Draw the waves */
+
+  x1 = x0 - (x0 % dx);
+  x2 = x1 + dx;
+  odd = (x1/dx) % 2;
+  y1 = y2 = y0;
+
+  if (odd)
+    y1 += dy;
+  else
+    y2 += dy;
+
+  MoveToEx (s->hdc, x1, y1, NULL);
+
+  while (x1 <= xmax)
+    {
+      LineTo (s->hdc, x2, y2);
+      x1  = x2, y1 = y2;
+      x2 += dx, y2 = y0 + odd*dy;
+      odd = !odd;
+    }
+
+  /* Restore previous pen and clipping rectangle(s) */
+  w32_restore_glyph_string_clip (s);
+  SelectObject (s->hdc, oldhp);
+  DeleteObject (hp);
+}
 
 /* Draw a hollow rectangle at the specified position.  */
 void
@@ -2343,60 +2430,74 @@ x_draw_glyph_string (struct glyph_string *s)
       /* Draw underline.  */
       if (s->face->underline_p)
         {
-          unsigned long thickness, position;
-          int y;
-
-          if (s->prev && s->prev->face->underline_p)
+          if (s->face->underline_type == FACE_UNDER_WAVE)
             {
-              /* We use the same underline style as the previous one.  */
-              thickness = s->prev->underline_thickness;
-              position = s->prev->underline_position;
+              COLORREF color;
+
+              if (s->face->underline_defaulted_p)
+                color = s->gc->foreground;
+              else
+                color = s->face->underline_color;
+
+              w32_draw_underwave (s, color);
             }
-          else
+          else if (s->face->underline_type == FACE_UNDER_LINE)
             {
-              /* Get the underline thickness.  Default is 1 pixel.  */
-              if (s->font && s->font->underline_thickness > 0)
-                thickness = s->font->underline_thickness;
+              unsigned long thickness, position;
+              int y;
+
+              if (s->prev && s->prev->face->underline_p)
+                {
+                  /* We use the same underline style as the previous one.  */
+                  thickness = s->prev->underline_thickness;
+                  position = s->prev->underline_position;
+                }
               else
-                thickness = 1;
-              if (x_underline_at_descent_line)
-                position = (s->height - thickness) - (s->ybase - s->y);
+                {
+                  /* Get the underline thickness.  Default is 1 pixel.  */
+                  if (s->font && s->font->underline_thickness > 0)
+                    thickness = s->font->underline_thickness;
+                  else
+                    thickness = 1;
+                  if (x_underline_at_descent_line)
+                    position = (s->height - thickness) - (s->ybase - s->y);
+                  else
+                    {
+                      /* Get the underline position.  This is the recommended
+                         vertical offset in pixels from the baseline to the top of
+                         the underline.  This is a signed value according to the
+                         specs, and its default is
+
+                         ROUND ((maximum_descent) / 2), with
+                         ROUND (x) = floor (x + 0.5)  */
+
+                      if (x_use_underline_position_properties
+                          && s->font && s->font->underline_position >= 0)
+                        position = s->font->underline_position;
+                      else if (s->font)
+                        position = (s->font->descent + 1) / 2;
+                    }
+                  position = max (position, underline_minimum_offset);
+                }
+              /* Check the sanity of thickness and position.  We should
+                 avoid drawing underline out of the current line area.  */
+              if (s->y + s->height <= s->ybase + position)
+                position = (s->height - 1) - (s->ybase - s->y);
+              if (s->y + s->height < s->ybase + position + thickness)
+                thickness = (s->y + s->height) - (s->ybase + position);
+              s->underline_thickness = thickness;
+              s->underline_position =position;
+              y = s->ybase + position;
+              if (s->face->underline_defaulted_p)
+                {
+                  w32_fill_area (s->f, s->hdc, s->gc->foreground, s->x,
+                                 y, s->width, 1);
+                }
               else
                 {
-                /* Get the underline position.  This is the recommended
-                   vertical offset in pixels from the baseline to the top of
-                   the underline.  This is a signed value according to the
-                   specs, and its default is
-
-                   ROUND ((maximum_descent) / 2), with
-                   ROUND (x) = floor (x + 0.5)  */
-
-                if (x_use_underline_position_properties
-                    && s->font && s->font->underline_position >= 0)
-                  position = s->font->underline_position;
-                else if (s->font)
-                  position = (s->font->descent + 1) / 2;
+                  w32_fill_area (s->f, s->hdc, s->face->underline_color, s->x,
+                                 y, s->width, 1);
                 }
-	      position = max (position, underline_minimum_offset);
-            }
-	  /* Check the sanity of thickness and position.  We should
-	     avoid drawing underline out of the current line area.  */
-	  if (s->y + s->height <= s->ybase + position)
-	    position = (s->height - 1) - (s->ybase - s->y);
-	  if (s->y + s->height < s->ybase + position + thickness)
-	    thickness = (s->y + s->height) - (s->ybase + position);
-	  s->underline_thickness = thickness;
-	  s->underline_position =position;
-          y = s->ybase + position;
-          if (s->face->underline_defaulted_p)
-            {
-              w32_fill_area (s->f, s->hdc, s->gc->foreground, s->x,
-                             y, s->width, 1);
-            }
-          else
-            {
-              w32_fill_area (s->f, s->hdc, s->face->underline_color, s->x,
-                             y, s->width, 1);
             }
         }
       /* Draw overline.  */
diff --git a/src/xfaces.c b/src/xfaces.c
index 617097d..8bee2d6 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -320,6 +320,7 @@ static Lisp_Object QCfontset;
 
 Lisp_Object Qnormal;
 Lisp_Object Qbold;
+static Lisp_Object Qline, Qwave;
 static Lisp_Object Qultra_light, Qextra_light, Qlight;
 static Lisp_Object Qsemi_light, Qsemi_bold, Qextra_bold, Qultra_bold;
 static Lisp_Object Qoblique, Qreverse_oblique, Qreverse_italic;
@@ -1889,7 +1890,8 @@ check_lface_attrs (Lisp_Object *attrs)
   xassert (UNSPECIFIEDP (attrs[LFACE_UNDERLINE_INDEX])
 	   || IGNORE_DEFFACE_P (attrs[LFACE_UNDERLINE_INDEX])
 	   || SYMBOLP (attrs[LFACE_UNDERLINE_INDEX])
-	   || STRINGP (attrs[LFACE_UNDERLINE_INDEX]));
+	   || STRINGP (attrs[LFACE_UNDERLINE_INDEX])
+	   || CONSP (attrs[LFACE_UNDERLINE_INDEX]));
   xassert (UNSPECIFIEDP (attrs[LFACE_OVERLINE_INDEX])
 	   || IGNORE_DEFFACE_P (attrs[LFACE_OVERLINE_INDEX])
 	   || SYMBOLP (attrs[LFACE_OVERLINE_INDEX])
@@ -2520,7 +2522,8 @@ merge_face_ref (struct frame *f, Lisp_Object face_ref, Lisp_Object *to,
 		{
 		  if (EQ (value, Qt)
 		      || NILP (value)
-		      || STRINGP (value))
+		      || STRINGP (value)
+		      || CONSP (value))
 		    to[LFACE_UNDERLINE_INDEX] = value;
 		  else
 		    err = 1;
@@ -2944,15 +2947,54 @@ FRAME 0 means change the face on all frames, and change the default
     }
   else if (EQ (attr, QCunderline))
     {
-      if (!UNSPECIFIEDP (value) && !IGNORE_DEFFACE_P (value))
-	if ((SYMBOLP (value)
-	     && !EQ (value, Qt)
-	     && !EQ (value, Qnil))
-	    /* Underline color.  */
-	    || (STRINGP (value)
-		&& SCHARS (value) == 0))
-	  signal_error ("Invalid face underline", value);
-
+      int valid_p = 0;
+      
+      if (UNSPECIFIEDP (value) || IGNORE_DEFFACE_P (value))
+	valid_p = 1;
+      else if (NILP (value) || EQ (value, Qt))
+        valid_p = 1;
+      else if (STRINGP (value) && SCHARS (value) > 0)
+        valid_p = 1;
+      else if (CONSP (value))
+        {
+          Lisp_Object key, val, list;
+
+          list = value;
+          valid_p = 1;
+
+          while (!NILP (CAR_SAFE(list)))
+            {
+              key = CAR_SAFE (list);
+              list = CDR_SAFE (list);
+              val = CAR_SAFE (list);
+              list = CDR_SAFE (list);
+            
+              if(NILP (key) || NILP (val)) 
+                {
+                  valid_p = 0;
+                  break;
+                }
+
+              else if (EQ (key, QCcolor)
+                       && !(EQ (val, Qforeground_color)
+                            || (STRINGP (val) && SCHARS (val) > 0)))
+                {
+                  valid_p = 0;
+                  break;
+                }
+              
+              else if (EQ (key, QCstyle) 
+                       && !(EQ (val, Qline) || EQ (val, Qwave)))
+                {
+                  valid_p = 0;
+                  break;
+                }
+            }
+        }
+      
+      if (!valid_p)
+        signal_error ("Invalid face underline", value);
+      
       old_value = LFACE_UNDERLINE (lface);
       LFACE_UNDERLINE (lface) = value;
     }
@@ -3762,6 +3804,7 @@ Value is nil if ATTR doesn't have a discrete set of valid values.  */)
 
   CHECK_SYMBOL (attr);
 
+  /* XXX: no check for QCbox? */
   if (EQ (attr, QCunderline))
     result = Fcons (Qt, Fcons (Qnil, Qnil));
   else if (EQ (attr, QCoverline))
@@ -5563,7 +5606,7 @@ realize_x_face (struct face_cache *cache, Lisp_Object *attrs)
 #ifdef HAVE_WINDOW_SYSTEM
   struct face *default_face;
   struct frame *f;
-  Lisp_Object stipple, overline, strike_through, box;
+  Lisp_Object stipple, underline, overline, strike_through, box;
 
   xassert (FRAME_WINDOW_P (cache->f));
 
@@ -5696,29 +5739,76 @@ realize_x_face (struct face_cache *cache, Lisp_Object *attrs)
 
   /* Text underline, overline, strike-through.  */
 
-  if (EQ (attrs[LFACE_UNDERLINE_INDEX], Qt))
+  underline = attrs[LFACE_UNDERLINE_INDEX];
+  if (EQ (underline, Qt))
     {
       /* Use default color (same as foreground color).  */
       face->underline_p = 1;
+      face->underline_type = FACE_UNDER_LINE;
       face->underline_defaulted_p = 1;
       face->underline_color = 0;
     }
-  else if (STRINGP (attrs[LFACE_UNDERLINE_INDEX]))
+  else if (STRINGP (underline))
     {
       /* Use specified color.  */
       face->underline_p = 1;
+      face->underline_type = FACE_UNDER_LINE;
       face->underline_defaulted_p = 0;
       face->underline_color
-	= load_color (f, face, attrs[LFACE_UNDERLINE_INDEX],
+	= load_color (f, face, underline,
 		      LFACE_UNDERLINE_INDEX);
     }
-  else if (NILP (attrs[LFACE_UNDERLINE_INDEX]))
+  else if (NILP (underline))
     {
       face->underline_p = 0;
       face->underline_defaulted_p = 0;
       face->underline_color = 0;
     }
-
+  else if (CONSP (underline))
+    {
+      /* `(:color COLOR :style STYLE)'.  
+         STYLE being one of `line' or `wave'. */
+      face->underline_p = 1;
+      face->underline_color = 0;
+      face->underline_defaulted_p = 1;
+      face->underline_type = FACE_UNDER_LINE;
+
+      while (CONSP (underline))
+        {
+          Lisp_Object keyword, value;
+
+          keyword = XCAR (underline);
+          underline = XCDR (underline);
+
+          if (!CONSP (underline))
+            break;
+          value = XCAR (underline);
+          underline = XCDR (underline);
+
+          if (EQ (keyword, QCcolor))
+            {
+              if (EQ (value, Qforeground_color))
+                {
+                  face->underline_defaulted_p = 1;
+                  face->underline_color = 0;
+                }
+              else if (STRINGP (value))
+                {
+                  face->underline_defaulted_p = 0;
+                  face->underline_color = load_color (f, face, value,
+                                                      LFACE_UNDERLINE_INDEX);
+                }
+            }
+          else if (EQ (keyword, QCstyle))
+            {
+              if (EQ (value, Qline))
+                face->underline_type = FACE_UNDER_LINE;
+              else if (EQ (value, Qwave))
+                face->underline_type = FACE_UNDER_WAVE;
+            }
+        }
+    }
+  
   overline = attrs[LFACE_OVERLINE_INDEX];
   if (STRINGP (overline))
     {
@@ -6465,6 +6555,8 @@ syms_of_xfaces (void)
   DEFSYM (QCcolor, ":color");
   DEFSYM (QCline_width, ":line-width");
   DEFSYM (QCstyle, ":style");
+  DEFSYM (Qline, "line");
+  DEFSYM (Qwave, "wave");
   DEFSYM (Qreleased_button, "released-button");
   DEFSYM (Qpressed_button, "pressed-button");
   DEFSYM (Qnormal, "normal");
diff --git a/src/xterm.c b/src/xterm.c
index 4b34d63..a58e366 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -2653,6 +2653,65 @@ x_draw_stretch_glyph_string (struct glyph_string *s)
   s->background_filled_p = 1;
 }
 
+/*
+   Draw a wavy line under S. The wave fills wave_height pixels from y0.
+
+                    x0         wave_length = 2
+                                 --
+                y0   *   *   *   *   *
+                     |* * * * * * * * *
+    wave_height = 3  | *   *   *   *
+
+*/
+
+static void
+x_draw_underwave (struct glyph_string *s)
+{
+  int wave_height = 2, wave_length = 3;
+  int dx, dy, x0, y0, width, x1, y1, x2, y2, odd, xmax;
+  XRectangle wave_clip, string_clip, final_clip;
+
+  dx = wave_length;
+  dy = wave_height - 1;
+  x0 = s->x;
+  y0 = s->ybase + 1;
+  width = s->width;
+  xmax = x0 + width;
+
+  /* Find and set clipping rectangle */
+
+  wave_clip = (XRectangle){ x0, y0, width, wave_height };
+  get_glyph_string_clip_rect (s, &string_clip);
+
+  if (!x_intersect_rectangles (&wave_clip, &string_clip, &final_clip))
+    return;
+
+  XSetClipRectangles (s->display, s->gc, 0, 0, &final_clip, 1, Unsorted);
+
+  /* Draw the waves */
+
+  x1 = x0 - (x0 % dx);
+  x2 = x1 + dx;
+  odd = (x1/dx) % 2;
+  y1 = y2 = y0;
+
+  if (odd)
+    y1 += dy;
+  else
+    y2 += dy;
+
+  while (x1 <= xmax)
+    {
+      XDrawLine (s->display, s->window, s->gc, x1, y1, x2, y2);
+      x1  = x2, y1 = y2;
+      x2 += dx, y2 = y0 + odd*dy;
+      odd = !odd;
+    }
+
+  /* Restore previous clipping rectangle(s) */
+  XSetClipRectangles (s->display, s->gc, 0, 0, s->clip, s->num_clips, Unsorted);
+}
+
 
 /* Draw glyph string S.  */
 
@@ -2755,68 +2814,83 @@ x_draw_glyph_string (struct glyph_string *s)
     {
       /* Draw underline.  */
       if (s->face->underline_p)
-	{
-	  unsigned long thickness, position;
-	  int y;
-
-	  if (s->prev && s->prev->face->underline_p)
-	    {
-	      /* We use the same underline style as the previous one.  */
-	      thickness = s->prev->underline_thickness;
-	      position = s->prev->underline_position;
-	    }
-	  else
-	    {
-	      /* Get the underline thickness.  Default is 1 pixel.  */
-	      if (s->font && s->font->underline_thickness > 0)
-		thickness = s->font->underline_thickness;
-	      else
-		thickness = 1;
-	      if (x_underline_at_descent_line)
-		position = (s->height - thickness) - (s->ybase - s->y);
-	      else
-		{
-		  /* Get the underline position.  This is the recommended
-		     vertical offset in pixels from the baseline to the top of
-		     the underline.  This is a signed value according to the
-		     specs, and its default is
-
-		     ROUND ((maximum descent) / 2), with
-		     ROUND(x) = floor (x + 0.5)  */
-
-		  if (x_use_underline_position_properties
-		      && s->font && s->font->underline_position >= 0)
-		    position = s->font->underline_position;
-		  else if (s->font)
-		    position = (s->font->descent + 1) / 2;
-		  else
-		    position = underline_minimum_offset;
-		}
-	      position = max (position, underline_minimum_offset);
-	    }
-	  /* Check the sanity of thickness and position.  We should
-	     avoid drawing underline out of the current line area.  */
-	  if (s->y + s->height <= s->ybase + position)
-	    position = (s->height - 1) - (s->ybase - s->y);
-	  if (s->y + s->height < s->ybase + position + thickness)
-	    thickness = (s->y + s->height) - (s->ybase + position);
-	  s->underline_thickness = thickness;
-	  s->underline_position = position;
-	  y = s->ybase + position;
-	  if (s->face->underline_defaulted_p)
-	    XFillRectangle (s->display, s->window, s->gc,
-			    s->x, y, s->width, thickness);
-	  else
-	    {
-	      XGCValues xgcv;
-	      XGetGCValues (s->display, s->gc, GCForeground, &xgcv);
-	      XSetForeground (s->display, s->gc, s->face->underline_color);
-	      XFillRectangle (s->display, s->window, s->gc,
-			      s->x, y, s->width, thickness);
-	      XSetForeground (s->display, s->gc, xgcv.foreground);
-	    }
-	}
+        {
+          if (s->face->underline_type == FACE_UNDER_WAVE)
+            {
+              if (s->face->underline_defaulted_p)
+                x_draw_underwave (s);
+              else
+                {
+                  XGCValues xgcv;
+                  XGetGCValues (s->display, s->gc, GCForeground, &xgcv);
+                  XSetForeground (s->display, s->gc, s->face->underline_color);
+                  x_draw_underwave (s);
+                  XSetForeground (s->display, s->gc, xgcv.foreground);
+                }
+            }
+          else if (s->face->underline_type == FACE_UNDER_LINE)
+            {
+              unsigned long thickness, position;
+              int y;
 
+              if (s->prev && s->prev->face->underline_p)
+                {
+                  /* We use the same underline style as the previous one.  */
+                  thickness = s->prev->underline_thickness;
+                  position = s->prev->underline_position;
+                }
+              else
+                {
+                  /* Get the underline thickness.  Default is 1 pixel.  */
+                  if (s->font && s->font->underline_thickness > 0)
+                    thickness = s->font->underline_thickness;
+                  else
+                    thickness = 1;
+                  if (x_underline_at_descent_line)
+                    position = (s->height - thickness) - (s->ybase - s->y);
+                  else
+                    {
+                      /* Get the underline position.  This is the recommended
+                         vertical offset in pixels from the baseline to the top of
+                         the underline.  This is a signed value according to the
+                         specs, and its default is
+
+                         ROUND ((maximum descent) / 2), with
+                         ROUND(x) = floor (x + 0.5)  */
+
+                      if (x_use_underline_position_properties
+                          && s->font && s->font->underline_position >= 0)
+                        position = s->font->underline_position;
+                      else if (s->font)
+                        position = (s->font->descent + 1) / 2;
+                      else
+                        position = underline_minimum_offset;
+                    }
+                  position = max (position, underline_minimum_offset);
+                }
+              /* Check the sanity of thickness and position.  We should
+                 avoid drawing underline out of the current line area.  */
+              if (s->y + s->height <= s->ybase + position)
+                position = (s->height - 1) - (s->ybase - s->y);
+              if (s->y + s->height < s->ybase + position + thickness)
+                thickness = (s->y + s->height) - (s->ybase + position);
+              s->underline_thickness = thickness;
+              s->underline_position = position;
+              y = s->ybase + position;
+              if (s->face->underline_defaulted_p)
+                XFillRectangle (s->display, s->window, s->gc,
+                                s->x, y, s->width, thickness);
+              else
+                {
+                  XGCValues xgcv;
+                  XGetGCValues (s->display, s->gc, GCForeground, &xgcv);
+                  XSetForeground (s->display, s->gc, s->face->underline_color);
+                  XFillRectangle (s->display, s->window, s->gc,
+                                  s->x, y, s->width, thickness);
+                  XSetForeground (s->display, s->gc, xgcv.foreground);
+                }
+            }
+        }
       /* Draw overline.  */
       if (s->face->overline_p)
 	{