Simplify struct face to use only underline.

    * src/dispextern.h (enum face_underline_type): Add FACE_NO_UNDERLINE = 0.
    (struct face): Merge `underline_type` and `underline_p` into `underline`.
    Update all the occurrences in src/xdisp.c, src/xfaces.c, and src/xterm.c.

src/dispextern.h

@@ -1564,6 +1564,7 @@ enum lface_attribute_index
   LFACE_INHERIT_INDEX,
   LFACE_FONTSET_INDEX,
   LFACE_DISTANT_FOREGROUND_INDEX,
+  LFACE_EXTEND_INDEX,
   LFACE_VECTOR_SIZE
 };
 
@@ -1589,6 +1590,7 @@ enum face_box_type
 
 enum face_underline_type
 {
+  FACE_NO_UNDERLINE = 0,
   FACE_UNDER_LINE,
   FACE_UNDER_WAVE
 };
@@ -1663,7 +1665,7 @@ struct face
   ENUM_BF (face_box_type) box : 2;
 
   /* Style of underlining. */
-  ENUM_BF (face_underline_type) underline_type : 1;
+  ENUM_BF (face_underline_type) underline : 2;
 
   /* If `box' above specifies a 3D type, true means use box_color for
      drawing shadows.  */
@@ -1671,7 +1673,6 @@ struct face
 
   /* Non-zero if text in this face should be underlined, overlined,
      strike-through or have a box drawn around it.  */
-  bool_bf underline_p : 1;
   bool_bf overline_p : 1;
   bool_bf strike_through_p : 1;
 
@@ -1681,14 +1682,10 @@ struct face
   bool_bf foreground_defaulted_p : 1;
   bool_bf background_defaulted_p : 1;
 
-  /* True means that either no color is specified for underlining or that
-     the specified color couldn't be loaded.  Use the foreground
-     color when drawing in that case. */
-  bool_bf underline_defaulted_p : 1;
-
   /* True means that either no color is specified for the corresponding
      attribute or that the specified color couldn't be loaded.
      Use the foreground color when drawing in that case. */
+  bool_bf underline_defaulted_p : 1;
   bool_bf overline_color_defaulted_p : 1;
   bool_bf strike_through_color_defaulted_p : 1;
   bool_bf box_color_defaulted_p : 1;

src/nsterm.m

@@ -3404,9 +3404,9 @@ Note that CURSOR_WIDTH is meaningful only for (h)bar cursors.
     return;
 
   /* Do underline.  */
-  if (face->underline_p)
+  if (face->underline)
     {
-      if (s->face->underline_type == FACE_UNDER_WAVE)
+      if (s->face->underline == FACE_UNDER_WAVE)
         {
           if (face->underline_defaulted_p)
             [defaultCol set];
@@ -3415,15 +3415,15 @@ Note that CURSOR_WIDTH is meaningful only for (h)bar cursors.
 
           ns_draw_underwave (s, width, x);
         }
-      else if (s->face->underline_type == FACE_UNDER_LINE)
+      else if (s->face->underline == FACE_UNDER_LINE)
         {
 
           NSRect r;
           unsigned long thickness, position;
 
           /* If the prev was underlined, match its appearance.  */
-          if (s->prev && s->prev->face->underline_p
-	      && s->prev->face->underline_type == FACE_UNDER_LINE
+          if (s->prev
+	      && s->prev->face->underline == FACE_UNDER_LINE
               && s->prev->underline_thickness > 0)
             {
               thickness = s->prev->underline_thickness;

src/w32term.c

@@ -2479,9 +2479,9 @@ w32_draw_glyph_string (struct glyph_string *s)
   if (!s->for_overlaps)
     {
       /* Draw underline.  */
-      if (s->face->underline_p)
+      if (s->face->underline)
         {
-          if (s->face->underline_type == FACE_UNDER_WAVE)
+          if (s->face->underline == FACE_UNDER_WAVE)
             {
               COLORREF color;
 
@@ -2492,13 +2492,13 @@ w32_draw_glyph_string (struct glyph_string *s)
 
               w32_draw_underwave (s, color);
             }
-          else if (s->face->underline_type == FACE_UNDER_LINE)
+          else if (s->face->underline == FACE_UNDER_LINE)
             {
               unsigned long thickness, position;
               int y;
 
-              if (s->prev && s->prev->face->underline_p
-		  && s->prev->face->underline_type == FACE_UNDER_LINE)
+              if (s->prev
+	          && s->prev->face->underline == FACE_UNDER_LINE)
                 {
                   /* We use the same underline style as the previous one.  */
                   thickness = s->prev->underline_thickness;
@@ -2512,7 +2512,7 @@ w32_draw_glyph_string (struct glyph_string *s)
 		  BOOL use_underline_position_properties;
 		  Lisp_Object val
 		    = buffer_local_value (Qunderline_minimum_offset,
-					s->w->contents);
+		                          s->w->contents);
 		  if (FIXNUMP (val))
 		    minimum_offset = max (0, XFIXNUM (val));
 		  else

src/xdisp.c

@@ -27367,7 +27367,7 @@ font_for_underline_metrics (struct glyph_string *s)
   for (g = s->first_glyph - 1; g >= g0; g--)
     {
       struct face *prev_face = FACE_FROM_ID (s->f, g->face_id);
-      if (!(prev_face && prev_face->underline_p))
+      if (!(prev_face && prev_face->underline != FACE_NO_UNDERLINE))
 	break;
     }
 

src/xfaces.c

@@ -1209,7 +1209,7 @@ free_face_colors (struct frame *f, struct face *face)
       IF_DEBUG (--ncolors_allocated);
     }
 
-  if (face->underline_p
+  if (face->underline
       && !face->underline_defaulted_p)
     {
       x_free_colors (f, &face->underline_color, 1);
@@ -5694,16 +5694,14 @@ realize_gui_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE]
   if (EQ (underline, Qt))
     {
       /* Use default color (same as foreground color).  */
-      face->underline_p = true;
-      face->underline_type = FACE_UNDER_LINE;
+      face->underline = FACE_UNDER_LINE;
       face->underline_defaulted_p = true;
       face->underline_color = 0;
     }
   else if (STRINGP (underline))
     {
       /* Use specified color.  */
-      face->underline_p = true;
-      face->underline_type = FACE_UNDER_LINE;
+      face->underline = FACE_UNDER_LINE;
       face->underline_defaulted_p = false;
       face->underline_color
 	= load_color (f, face, underline,
@@ -5711,7 +5709,7 @@ realize_gui_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE]
     }
   else if (NILP (underline))
     {
-      face->underline_p = false;
+      face->underline = FACE_NO_UNDERLINE;
       face->underline_defaulted_p = false;
       face->underline_color = 0;
     }
@@ -5719,10 +5717,9 @@ realize_gui_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE]
     {
       /* `(:color COLOR :style STYLE)'.
          STYLE being one of `line' or `wave'. */
-      face->underline_p = true;
+      face->underline = FACE_UNDER_LINE;
       face->underline_color = 0;
       face->underline_defaulted_p = true;
-      face->underline_type = FACE_UNDER_LINE;
 
       /* FIXME?  This is also not robust about checking the precise form.
          See comments in Finternal_set_lisp_face_attribute.  */
@@ -5755,9 +5752,9 @@ realize_gui_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE]
           else if (EQ (keyword, QCstyle))
             {
               if (EQ (value, Qline))
-                face->underline_type = FACE_UNDER_LINE;
+                face->underline = FACE_UNDER_LINE;
               else if (EQ (value, Qwave))
-                face->underline_type = FACE_UNDER_WAVE;
+                face->underline = FACE_UNDER_WAVE;
             }
         }
     }
@@ -6292,9 +6289,8 @@ merge_faces (struct window *w, Lisp_Object face_name, int face_id,
 {
   struct frame *f = WINDOW_XFRAME (w);
   Lisp_Object attrs[LFACE_VECTOR_SIZE];
-  struct face *base_face;
+  struct face *base_face = FACE_FROM_ID_OR_NULL (f, base_face_id);
 
-  base_face = FACE_FROM_ID_OR_NULL (f, base_face_id);
   if (!base_face)
     return base_face_id;
 
@@ -6319,12 +6315,14 @@ merge_faces (struct window *w, Lisp_Object face_name, int face_id,
     }
   else
     {
-      struct face *face;
       if (face_id < 0)
 	return base_face_id;
-      face = FACE_FROM_ID_OR_NULL (f, face_id);
+
+      struct face *face = FACE_FROM_ID_OR_NULL (f, face_id);
+
       if (!face)
 	return base_face_id;
+
       merge_face_vectors (w, f, face->lface, attrs, 0);
     }
 
@@ -6412,7 +6410,7 @@ dump_realized_face (struct face *face)
 #endif
   fprintf (stderr, "fontset: %d\n", face->fontset);
   fprintf (stderr, "underline: %d (%s)\n",
-	   face->underline_p,
+	   face->underline,
 	   SDATA (Fsymbol_name (face->lface[LFACE_UNDERLINE_INDEX])));
   fprintf (stderr, "hash: %" PRIuPTR "\n", face->hash);
 }

src/xterm.c

@@ -3798,9 +3798,9 @@ x_draw_glyph_string (struct glyph_string *s)
   if (!s->for_overlaps)
     {
       /* Draw underline.  */
-      if (s->face->underline_p)
+      if (s->face->underline)
         {
-          if (s->face->underline_type == FACE_UNDER_WAVE)
+          if (s->face->underline == FACE_UNDER_WAVE)
             {
               if (s->face->underline_defaulted_p)
                 x_draw_underwave (s);
@@ -3814,13 +3814,13 @@ x_draw_glyph_string (struct glyph_string *s)
                   XSetForeground (display, s->gc, xgcv.foreground);
                 }
             }
-          else if (s->face->underline_type == FACE_UNDER_LINE)
+          else if (s->face->underline == FACE_UNDER_LINE)
             {
               unsigned long thickness, position;
               int y;
 
-              if (s->prev && s->prev->face->underline_p
-		  && s->prev->face->underline_type == FACE_UNDER_LINE)
+              if (s->prev &&
+	          s->prev->face->underline == FACE_UNDER_LINE)
                 {
                   /* We use the same underline style as the previous one.  */
                   thickness = s->prev->underline_thickness;