Allow controlling the underline position of faces

* doc/lispref/display.texi (Face Attributes): Document new
`:position' property of the `:underline' attribute.
* etc/NEWS: Announce new property.
* lisp/cus-face.el (custom-face-attributes): Implement
customization for new face attribute.
* src/dispextern.h (struct face): New fields
`underline_pixels_above_descent_line' and
`underline_at_descent_line_p'.
* src/haikuterm.c (haiku_draw_text_decoration):
* src/nsterm.m (ns_draw_text_decoration):
* src/w32term.c (w32_draw_glyph_string):
* src/xterm.c (x_draw_glyph_string): Respect new face fields.

* src/xfaces.c (realize_gui_face): Handle new `:position'
keyword.
(syms_of_xfaces): New symbol `:position'.

1 files changed, 16 insertions, 0 deletions

diff --git a/src/xfaces.c b/src/xfaces.c
index 3fd31b7f225..8064d47c947 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -6041,6 +6041,8 @@ realize_gui_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE]
       face->underline = FACE_UNDER_LINE;
       face->underline_defaulted_p = true;
       face->underline_color = 0;
+      face->underline_at_descent_line_p = false;
+      face->underline_pixels_above_descent_line = 0;
     }
   else if (STRINGP (underline))
     {
@@ -6050,12 +6052,16 @@ realize_gui_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE]
       face->underline_color
 	= load_color (f, face, underline,
 		      LFACE_UNDERLINE_INDEX);
+      face->underline_at_descent_line_p = false;
+      face->underline_pixels_above_descent_line = 0;
     }
   else if (NILP (underline))
     {
       face->underline = FACE_NO_UNDERLINE;
       face->underline_defaulted_p = false;
       face->underline_color = 0;
+      face->underline_at_descent_line_p = false;
+      face->underline_pixels_above_descent_line = 0;
     }
   else if (CONSP (underline))
     {
@@ -6064,6 +6070,8 @@ realize_gui_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE]
       face->underline = FACE_UNDER_LINE;
       face->underline_color = 0;
       face->underline_defaulted_p = true;
+      face->underline_at_descent_line_p = false;
+      face->underline_pixels_above_descent_line = 0;
 
       /* FIXME?  This is also not robust about checking the precise form.
          See comments in Finternal_set_lisp_face_attribute.  */
@@ -6100,6 +6108,13 @@ realize_gui_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE]
               else if (EQ (value, Qwave))
                 face->underline = FACE_UNDER_WAVE;
             }
+	  else if (EQ (keyword, QCposition))
+	    {
+	      face->underline_at_descent_line_p = !NILP (value);
+
+	      if (FIXNATP (value))
+		face->underline_pixels_above_descent_line = XFIXNAT (value);
+	    }
         }
     }
 
@@ -6915,6 +6930,7 @@ syms_of_xfaces (void)
   DEFSYM (QCcolor, ":color");
   DEFSYM (QCline_width, ":line-width");
   DEFSYM (QCstyle, ":style");
+  DEFSYM (QCposition, ":position");
   DEFSYM (Qline, "line");
   DEFSYM (Qwave, "wave");
   DEFSYM (Qreleased_button, "released-button");