Port double-line underlines to GUI systems

* src/xterm.c (x_get_scale_factor): Replace display in first
argument with a pointer to dpyinfo.
(x_draw_underwave): Adjust to match.
(x_draw_glyph_string): Implement double-line underlines.

* src/androidterm.c (android_get_scale_factor)
(android_draw_glyph_string):

* src/haikuterm.c (haiku_draw_text_decoration):

* src/nsterm.m (ns_draw_text_decoration):

* src/pgtkterm.c (pgtk_draw_glyph_string):

* src/w32term.c (w32_draw_glyph_string): Synchronize with X.

* src/xfaces.c (realize_gui_face): Enable `double-line' on
window systems.

7 files changed, 181 insertions, 77 deletions

diff --git a/src/androidterm.c b/src/androidterm.c
index f5173168785..9f25c507a23 100644
--- a/src/androidterm.c
+++ b/src/androidterm.c
@@ -3740,19 +3740,15 @@ static void
 android_get_scale_factor (int *scale_x, int *scale_y)
 {
   /* This is 96 everywhere else, but 160 on Android.  */
-  const int base_res = 160;
-  struct android_display_info *dpyinfo;
+  int base_res = 160;
 
-  dpyinfo = x_display_list;
   *scale_x = *scale_y = 1;
+  eassert (x_display_list);
 
-  if (dpyinfo)
-    {
-      if (dpyinfo->resx > base_res)
-	*scale_x = floor (dpyinfo->resx / base_res);
-      if (dpyinfo->resy > base_res)
-	*scale_y = floor (dpyinfo->resy / base_res);
-    }
+  if (x_display_list->resx > base_res)
+    *scale_x = floor (x_display_list->resx / base_res);
+  if (x_display_list->resy > base_res)
+    *scale_y = floor (x_display_list->resy / base_res);
 }
 
 static void
@@ -4171,13 +4167,16 @@ android_draw_glyph_string (struct glyph_string *s)
                   android_set_foreground (s->gc, xgcv.foreground);
                 }
             }
-          else if (s->face->underline == FACE_UNDERLINE_SINGLE)
+          else if (s->face->underline == FACE_UNDERLINE_SINGLE
+		   || s->face->underline == FACE_UNDERLINE_DOUBLE_LINE)
             {
               unsigned long thickness, position;
               int y;
 
               if (s->prev
-		  && s->prev->face->underline == FACE_UNDERLINE_SINGLE
+		  && ((s->prev->face->underline == FACE_UNDERLINE_SINGLE)
+		      || (s->prev->face->underline
+			  == FACE_UNDERLINE_DOUBLE_LINE))
 		  && (s->prev->face->underline_at_descent_line_p
 		      == s->face->underline_at_descent_line_p)
 		  && (s->prev->face->underline_pixels_above_descent_line
@@ -4254,19 +4253,38 @@ android_draw_glyph_string (struct glyph_string *s)
                 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)
-                android_fill_rectangle (FRAME_ANDROID_DRAWABLE (s->f), s->gc,
-					s->x, y, decoration_width, thickness);
-              else
-                {
-                  struct android_gc_values xgcv;
-                  android_get_gc_values (s->gc, ANDROID_GC_FOREGROUND, &xgcv);
-                  android_set_foreground (s->gc, s->face->underline_color);
-                  android_fill_rectangle (FRAME_ANDROID_DRAWABLE (s->f), s->gc,
+
+	      {
+		struct android_gc_values xgcv;
+
+		y = s->ybase + position;
+		if (s->face->underline_defaulted_p)
+		  android_fill_rectangle (FRAME_ANDROID_DRAWABLE (s->f), s->gc,
 					  s->x, y, decoration_width, thickness);
-                  android_set_foreground (s->gc, xgcv.foreground);
-                }
+		else
+		  {
+		    android_get_gc_values (s->gc, ANDROID_GC_FOREGROUND, &xgcv);
+		    android_set_foreground (s->gc, s->face->underline_color);
+		    android_fill_rectangle (FRAME_ANDROID_DRAWABLE (s->f), s->gc,
+					    s->x, y, decoration_width, thickness);
+		  }
+
+		/* Place a second underline above the first if this was
+		   requested in the face specification.  */
+
+		if (s->face->underline == FACE_UNDERLINE_DOUBLE_LINE)
+		  {
+		    /* Compute the position of the second underline.  */
+		    position = position - thickness - 1;
+		    y        = s->ybase + position;
+		    android_fill_rectangle (FRAME_ANDROID_DRAWABLE (s->f),
+					    s->gc, s->x, y, decoration_width,
+					    thickness, false);
+		  }
+
+		if (!s->face->underline_defaulted_p)
+		  android_set_foreground (s->gc, xgcv.foreground);
+	      }
             }
         }
       /* Draw overline.  */
diff --git a/src/haikuterm.c b/src/haikuterm.c
index c3971bf6fe4..4a03c4cb2d5 100644
--- a/src/haikuterm.c
+++ b/src/haikuterm.c
@@ -829,13 +829,15 @@ haiku_draw_text_decoration (struct glyph_string *s, struct face *face,
 
       if (face->underline == FACE_UNDERLINE_WAVE)
 	haiku_draw_underwave (s, width, x);
-      else if (face->underline == FACE_UNDERLINE_SINGLE)
+      else if (face->underline == FACE_UNDERLINE_SINGLE
+	       || face->underline == FACE_UNDERLINE_DOUBLE_LINE))
 	{
 	  unsigned long thickness, position;
 	  int y;
 
 	  if (s->prev
-	      && s->prev->face->underline == FACE_UNDERLINE_SINGLE
+	      && (s->prev->face->underline == FACE_UNDERLINE_SINGLE
+		  || s->prev->face->underline == FACE_UNDERLINE_DOUBLE_LINE)
 	      && (s->prev->face->underline_at_descent_line_p
 		  == s->face->underline_at_descent_line_p)
 	      && (s->prev->face->underline_pixels_above_descent_line
@@ -911,6 +913,17 @@ haiku_draw_text_decoration (struct glyph_string *s, struct face *face,
 	  y = s->ybase + position;
 
 	  BView_FillRectangle (view, s->x, y, s->width, thickness);
+
+	  /* Place a second underline above the first if this was
+	     requested in the face specification.  */
+
+	  if (s->face->underline == FACE_UNDERLINE_DOUBLE_LINE)
+	    {
+	      /* Compute the position of the second underline.  */
+	      position = position - thickness - 1;
+	      y        = s->ybase + position;
+	      BView_FillRectangle (view, s->x, y, s->width, thickness);
+	    }
 	}
     }
 
diff --git a/src/nsterm.m b/src/nsterm.m
index 84d94b5be74..bd4010f2844 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -3337,7 +3337,8 @@ ns_draw_text_decoration (struct glyph_string *s, struct face *face,
 
           ns_draw_underwave (s, width, x);
         }
-      else if (s->face->underline == FACE_UNDERLINE_SINGLE)
+      else if (s->face->underline == FACE_UNDERLINE_SINGLE
+	       || s->face->underline == FACE_UNDERLINE_DOUBLE_LINE)
         {
 
           NSRect r;
@@ -3345,7 +3346,9 @@ ns_draw_text_decoration (struct glyph_string *s, struct face *face,
 
           /* If the prev was underlined, match its appearance.  */
           if (s->prev
-	      && s->prev->face->underline == FACE_UNDERLINE_SINGLE
+	      && ((s->prev->face->underline == FACE_UNDERLINE_SINGLE)
+		  || (s->prev->face->underline
+		      == FACE_UNDERLINE_DOUBLE_LINE))
               && s->prev->underline_thickness > 0
 	      && (s->prev->face->underline_at_descent_line_p
 		  == s->face->underline_at_descent_line_p)
@@ -3417,6 +3420,17 @@ ns_draw_text_decoration (struct glyph_string *s, struct face *face,
             [[NSColor colorWithUnsignedLong:face->underline_color] set];
 
           NSRectFill (r);
+
+	  /* Place a second underline above the first if this was
+	     requested in the face specification.  */
+
+	  if (s->face->underline == FACE_UNDERLINE_DOUBLE_LINE)
+	    {
+	      /* Compute the position of the second underline.  */
+	      position = position - thickness - 1;
+	      r = NSMakeRect (x, s->ybase + position, width, thickness);
+	      NSRectFill (r);
+	    }
         }
     }
   /* Do overline. We follow other terms in using a thickness of 1
diff --git a/src/pgtkterm.c b/src/pgtkterm.c
index e08e4b2b230..8441189ab8d 100644
--- a/src/pgtkterm.c
+++ b/src/pgtkterm.c
@@ -2553,13 +2553,17 @@ pgtk_draw_glyph_string (struct glyph_string *s)
 	      else
 		pgtk_draw_underwave (s, s->face->underline_color);
 	    }
-	  else if (s->face->underline == FACE_UNDERLINE_SINGLE)
+	  else if (s->face->underline == FACE_UNDERLINE_SINGLE
+		   || s->face->underline == FACE_UNDERLINE_DOUBLE_LINE)
 	    {
 	      unsigned long thickness, position;
 	      int y;
+	      unsigned long foreground;
 
 	      if (s->prev
-		  && s->prev->face->underline == FACE_UNDERLINE_SINGLE
+		  && ((s->prev->face->underline == FACE_UNDERLINE_SINGLE)
+		      || (s->prev->face->underline
+			  == FACE_UNDERLINE_DOUBLE_LINE))
 		  && (s->prev->face->underline_at_descent_line_p
 		      == s->face->underline_at_descent_line_p)
 		  && (s->prev->face->underline_pixels_above_descent_line
@@ -2616,15 +2620,25 @@ pgtk_draw_glyph_string (struct glyph_string *s)
 	      s->underline_thickness = thickness;
 	      s->underline_position = position;
 	      y = s->ybase + position;
+
 	      if (s->face->underline_defaulted_p)
-		pgtk_fill_rectangle (s->f, s->xgcv.foreground,
-				     s->x, y, s->width, thickness,
-				     false);
+		foreground = s->xgcv.foreground;
 	      else
+		foreground = s->face->underline_color;
+
+	      pgtk_fill_rectangle (s->f, foreground, s->x, y, s->width,
+				   thickness, false);
+
+	      /* Place a second underline above the first if this was
+		 requested in the face specification.  */
+
+	      if (s->face->underline == FACE_UNDERLINE_DOUBLE_LINE)
 		{
-		  pgtk_fill_rectangle (s->f, s->face->underline_color,
-				       s->x, y, s->width, thickness,
-				       false);
+		  /* Compute the position of the second underline.  */
+		  position = position - thickness - 1;
+		  y        = s->ybase + position;
+		  pgtk_fill_rectangle (s->f, foreground, s->x, y, s->width,
+				       thickness, false);
 		}
 	    }
 	}
diff --git a/src/w32term.c b/src/w32term.c
index 20ea346c8aa..a0037e6e090 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -2652,13 +2652,16 @@ w32_draw_glyph_string (struct glyph_string *s)
 
               w32_draw_underwave (s, color);
             }
-          else if (s->face->underline == FACE_UNDERLINE_SINGLE)
+          else if (s->face->underline == FACE_UNDERLINE_SINGLE
+		   || s->face->underline == FACE_UNDERLINE_DOUBLE_LINE)
             {
               unsigned long thickness, position;
               int y;
 
               if (s->prev
-		  && s->prev->face->underline == FACE_UNDERLINE_SINGLE
+		  && ((s->prev->face->underline == FACE_UNDERLINE_SINGLE)
+		      || (s->prev->face->underline
+			  == FACE_UNDERLINE_DOUBLE_LINE))
 		  && (s->prev->face->underline_at_descent_line_p
 		      == s->face->underline_at_descent_line_p)
 		  && (s->prev->face->underline_pixels_above_descent_line
@@ -2676,6 +2679,7 @@ w32_draw_glyph_string (struct glyph_string *s)
 		  BOOL use_underline_position_properties;
 		  Lisp_Object val = (WINDOW_BUFFER_LOCAL_VALUE
 				     (Qunderline_minimum_offset, s->w));
+		  COLORREF foreground;
 
 		  if (FIXNUMP (val))
 		    minimum_offset = max (0, XFIXNUM (val));
@@ -2734,18 +2738,28 @@ w32_draw_glyph_string (struct glyph_string *s)
               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;
+              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);
-                }
+		foreground = s->gc->foreground;
+	      else
+		foreground = s->face->underline_color;
+
+	      w32_fill_area (s->f, s->hdc, foreground, s->x, y,
+			     s->width, thickness);
+
+	      /* Place a second underline above the first if this was
+		 requested in the face specification.  */
+
+	      if (s->face->underline == FACE_UNDERLINE_DOUBLE_LINE)
+		{
+		  /* Compute the position of the second underline.  */
+		  position = position - thickness - 1;
+		  y        = s->ybase + position;
+		  w32_fill_area (s->f, s->hdc, foreground, s->x, y,
+				 s->width, thickness);
+		}
             }
         }
       /* Draw overline.  */
diff --git a/src/xfaces.c b/src/xfaces.c
index 07e198974fa..d9ee82c8e7f 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -6398,13 +6398,21 @@ realize_gui_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE]
             }
           else if (EQ (keyword, QCstyle))
             {
-              if (EQ (value, Qline))
-                face->underline = FACE_UNDERLINE_SINGLE;
-              else if (EQ (value, Qwave))
-                face->underline = FACE_UNDERLINE_WAVE;
-              else
-                face->underline = FACE_UNDERLINE_SINGLE;
-            }
+	      if (EQ (value, Qline))
+		face->underline = FACE_UNDERLINE_SINGLE;
+	      else if (EQ (value, Qdouble_line))
+		face->underline = FACE_UNDERLINE_DOUBLE_LINE;
+	      else if (EQ (value, Qwave))
+		face->underline = FACE_UNDERLINE_WAVE;
+#if 0
+	      else if (EQ (value, Qdots))
+		face->underline = FACE_UNDERLINE_DOTS;
+	      else if (EQ (value, Qdashes))
+		face->underline = FACE_UNDERLINE_DASHES;
+#endif /* 0 */
+	      else
+		face->underline = FACE_UNDERLINE_SINGLE;
+	    }
 	  else if (EQ (keyword, QCposition))
 	    {
 	      face->underline_at_descent_line_p = !NILP (value);
diff --git a/src/xterm.c b/src/xterm.c
index 360541ac0b9..9b014a7d0e4 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -10735,10 +10735,10 @@ x_draw_stretch_glyph_string (struct glyph_string *s)
 }
 
 static void
-x_get_scale_factor (Display *disp, int *scale_x, int *scale_y)
+x_get_scale_factor (struct x_display_info *dpyinfo,
+		    int *scale_x, int *scale_y)
 {
-  const int base_res = 96;
-  struct x_display_info * dpyinfo = x_display_info_for_display (disp);
+  int base_res = 96;
 
   *scale_x = *scale_y = 1;
 
@@ -10764,12 +10764,14 @@ x_get_scale_factor (Display *disp, int *scale_x, int *scale_y)
 static void
 x_draw_underwave (struct glyph_string *s, int decoration_width)
 {
-  Display *display = FRAME_X_DISPLAY (s->f);
-
+  Display *display;
+  struct x_display_info *dpyinfo;
   /* Adjust for scale/HiDPI.  */
   int scale_x, scale_y;
 
-  x_get_scale_factor (display, &scale_x, &scale_y);
+  dpyinfo = FRAME_DISPLAY_INFO (s->f);
+  display = dpyinfo->display;
+  x_get_scale_factor (dpyinfo, &scale_x, &scale_y);
 
   int wave_height = 3 * scale_y, wave_length = 2 * scale_x;
 
@@ -10971,13 +10973,16 @@ x_draw_glyph_string (struct glyph_string *s)
                   XSetForeground (display, s->gc, xgcv.foreground);
                 }
             }
-          else if (s->face->underline == FACE_UNDERLINE_SINGLE)
+          else if (s->face->underline == FACE_UNDERLINE_SINGLE
+		   || s->face->underline == FACE_UNDERLINE_DOUBLE_LINE)
             {
               unsigned long thickness, position;
               int y;
 
               if (s->prev
-		  && s->prev->face->underline == FACE_UNDERLINE_SINGLE
+		  && ((s->prev->face->underline == FACE_UNDERLINE_SINGLE)
+		      || (s->prev->face->underline
+			  == FACE_UNDERLINE_DOUBLE_LINE))
 		  && (s->prev->face->underline_at_descent_line_p
 		      == s->face->underline_at_descent_line_p)
 		  && (s->prev->face->underline_pixels_above_descent_line
@@ -11054,22 +11059,40 @@ x_draw_glyph_string (struct glyph_string *s)
                 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)
-                x_fill_rectangle (s->f, s->gc,
-				  s->x, y, decoration_width, thickness,
-				  false);
-              else
-                {
-                  Display *display = FRAME_X_DISPLAY (s->f);
-                  XGCValues xgcv;
-                  XGetGCValues (display, s->gc, GCForeground, &xgcv);
-                  XSetForeground (display, s->gc, s->face->underline_color);
-                  x_fill_rectangle (s->f, s->gc,
+
+	      {
+		Display *display = FRAME_X_DISPLAY (s->f);
+		XGCValues xgcv;
+
+		y = s->ybase + position;
+		if (s->face->underline_defaulted_p)
+		  x_fill_rectangle (s->f, s->gc,
 				    s->x, y, decoration_width, thickness,
 				    false);
-                  XSetForeground (display, s->gc, xgcv.foreground);
-                }
+		else
+		  {
+		    XGetGCValues (display, s->gc, GCForeground, &xgcv);
+		    XSetForeground (display, s->gc, s->face->underline_color);
+		    x_fill_rectangle (s->f, s->gc,
+				      s->x, y, decoration_width, thickness,
+				      false);
+		  }
+
+		/* Place a second underline above the first if this was
+		   requested in the face specification.  */
+
+		if (s->face->underline == FACE_UNDERLINE_DOUBLE_LINE)
+		  {
+		    /* Compute the position of the second underline.  */
+		    position = position - thickness - 1;
+		    y        = s->ybase + position;
+		    x_fill_rectangle (s->f, s->gc, s->x, y, decoration_width,
+				      thickness, false);
+		  }
+
+		if (!s->face->underline_defaulted_p)
+		  XSetForeground (display, s->gc, xgcv.foreground);
+	      }
             }
         }
       /* Draw overline.  */