Add :distant-foreground to faces.

* doc/lispref/display.texi (Face Attributes): Document :distant-foreground.

* etc/NEWS: Mention :distant-foreground.

* lisp/faces.el (face-x-resources): Add :distant-foreground.
(region): Use :distant-foreground for gtk and ns.

* src/dispextern.h (lface_attribute_index): Add
LFACE_DISTANT_FOREGROUND_INDEX.

* src/xfaces.c: Declare color_distance.
(QCdistant_foreground): New variable.
(NEAR_SAME_COLOR_THRESHOLD): New define.
(load_color2): New function.
(load_color): Call load_color2.
(load_face_colors): Call load_color2 and if distant-color is specified
calculate distant and use distant-color if colors are near.
(LFACE_DISTANT_FOREGROUND): New define.
(merge_face_ref, Finternal_set_lisp_face_attribute)
(Finternal_get_lisp_face_attribute)
(x_supports_face_attributes_p): Handle distant-foreground similar to
foreground.
(syms_of_xfaces): DEFSYM QCdistant_foreground.

9 files changed, 131 insertions, 31 deletions

diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index fa081f1e7aa..cc214aa6dfa 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,7 @@
+2013-11-01  Jan Djärv  <jan.h.d@swipnet.se>
+
+	* display.texi (Face Attributes): Document :distant-foreground.
+
 2013-10-30  Xue Fuqiao  <xfq.free@gmail.com>
 
 	* display.texi (Abstract Display): Improve indexing.
diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index 07ab2c6745f..ebb61a76b59 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -2036,6 +2036,15 @@ name, or a hexadecimal color specification.  @xref{Color Names}.  On
 black-and-white displays, certain shades of gray are implemented by
 stipple patterns.
 
+@item :distant-foreground
+Alternative foreground color, a string.  This is like @code{:foreground}
+but the color is only used as a foreground when the background color is
+near to the foreground that would have been used.  This is useful for
+example when marking text (i.e. the region face).  If the text has a foreground 
+that is visible with the region face, that foreground is used.
+If the foreground is near the region face background,
+@code{:distant-foreground} is used instead so the text is readable.
+
 @item :background
 Background color, a string.  The value can be a system-defined color
 name, or a hexadecimal color specification.  @xref{Color Names}.
diff --git a/etc/ChangeLog b/etc/ChangeLog
index 6527a7ab365..d35fa863441 100644
--- a/etc/ChangeLog
+++ b/etc/ChangeLog
@@ -1,3 +1,7 @@
+2013-11-01  Jan Djärv  <jan.h.d@swipnet.se>
+
+	* NEWS: Mention :distant-foreground.
+
 2013-10-16  Dmitry Gutov  <dgutov@yandex.ru>
 
 	* NEWS: Mention the homepage-related changes in package.el.
diff --git a/etc/NEWS b/etc/NEWS
index 1443173d255..4fed04da561 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -788,6 +788,10 @@ rather than inheriting from it (as do face specs set via Customize).
 *** New face characteristic (supports :underline (:style wave))
 specifies whether or not the terminal can display a wavy line.
 
+*** New face spec attribute :distant-foreground
+specifies foreground to use if background is near the foreground that would
+otherwise have been used.
+
 ** Image API
 
 +++
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 1493945af38..b71b808fec8 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2013-11-01  Jan Djärv  <jan.h.d@swipnet.se>
+
+	* faces.el (face-x-resources): Add :distant-foreground.
+	(region): Use :distant-foreground for gtk and ns.
+
 2013-11-01  Tassilo Horn  <tsdh@gnu.org>
 
 	Allow multiple bibliographies when BibLaTeX is used rathen than
diff --git a/lisp/faces.el b/lisp/faces.el
index 9aef744b037..8ff93874de0 100644
--- a/lisp/faces.el
+++ b/lisp/faces.el
@@ -274,6 +274,8 @@ If FRAME is omitted or nil, use the selected frame."
     (:weight (".attributeWeight" . "Face.AttributeWeight"))
     (:slant (".attributeSlant" . "Face.AttributeSlant"))
     (:foreground (".attributeForeground" . "Face.AttributeForeground"))
+    (:distant-foreground
+     (".attributeDistantForeground" . "Face.AttributeDistantForeground"))
     (:background (".attributeBackground" . "Face.AttributeBackground"))
     (:overline (".attributeOverline" . "Face.AttributeOverline"))
     (:strike-through (".attributeStrikeThrough" . "Face.AttributeStrikeThrough"))
@@ -2255,10 +2257,10 @@ terminal type to a different value."
   '((((class color) (min-colors 88) (background dark))
      :background "blue3")
     (((class color) (min-colors 88) (background light) (type gtk))
-     :foreground "gtk_selection_fg_color"
+     :distant-foreground "gtk_selection_fg_color"
      :background "gtk_selection_bg_color")
     (((class color) (min-colors 88) (background light) (type ns))
-     :foreground "ns_selection_fg_color"
+     :distant-foreground "ns_selection_fg_color"
      :background "ns_selection_bg_color")
     (((class color) (min-colors 88) (background light))
      :background "lightgoldenrod2")
diff --git a/src/ChangeLog b/src/ChangeLog
index d7cf7d47b0b..8186e220d7d 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,22 @@
+2013-11-01  Jan Djärv  <jan.h.d@swipnet.se>
+
+	* xfaces.c: Declare color_distance.
+	(QCdistant_foreground): New variable.
+	(NEAR_SAME_COLOR_THRESHOLD): New define.
+	(load_color2): New function.
+	(load_color): Call load_color2.
+	(load_face_colors): Call load_color2 and if distant-color is specified
+	calculate distant and use distant-color if colors are near.
+	(LFACE_DISTANT_FOREGROUND): New define.
+	(merge_face_ref, Finternal_set_lisp_face_attribute)
+	(Finternal_get_lisp_face_attribute)
+	(x_supports_face_attributes_p): Handle distant-foreground similar to
+	foreground.
+	(syms_of_xfaces): DEFSYM QCdistant_foreground.
+
+	* dispextern.h (lface_attribute_index): Add
+	LFACE_DISTANT_FOREGROUND_INDEX.
+
 2013-11-01  Claudio Bley  <claudio.bley@googlemail.com>
 
 	* image.c (pbm_next_char): New function.  See
diff --git a/src/dispextern.h b/src/dispextern.h
index dd64ae1921f..22357a01c84 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -1543,6 +1543,7 @@ enum lface_attribute_index
   LFACE_FONT_INDEX,
   LFACE_INHERIT_INDEX,
   LFACE_FONTSET_INDEX,
+  LFACE_DISTANT_FOREGROUND_INDEX,
   LFACE_VECTOR_SIZE
 };
 
diff --git a/src/xfaces.c b/src/xfaces.c
index f50fffc6419..72b62216abd 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -292,7 +292,7 @@ Lisp_Object QCwidth;
 static Lisp_Object QCfont, QCbold, QCitalic;
 static Lisp_Object QCreverse_video;
 static Lisp_Object QCoverline, QCstrike_through, QCbox, QCinherit;
-static Lisp_Object QCfontset;
+static Lisp_Object QCfontset, QCdistant_foreground;
 
 /* Symbols used for attribute values.  */
 
@@ -440,6 +440,7 @@ static struct face_cache *make_face_cache (struct frame *);
 static void free_face_cache (struct face_cache *);
 static int merge_face_ref (struct frame *, Lisp_Object, Lisp_Object *,
 			   int, struct named_merge_point *);
+static int color_distance (XColor *x, XColor *y);
 
 #ifdef HAVE_WINDOW_SYSTEM
 static void set_font_frame_param (Lisp_Object, Lisp_Object);
@@ -910,6 +911,8 @@ load_pixmap (struct frame *f, Lisp_Object name)
 				X Colors
  ***********************************************************************/
 
+#define NEAR_SAME_COLOR_THRESHOLD 30000
+
 /* Parse RGB_LIST, and fill in the RGB fields of COLOR.
    RGB_LIST should contain (at least) 3 lisp integers.
    Return 0 if there's a problem with RGB_LIST, otherwise return 1.  */
@@ -1176,24 +1179,10 @@ COLOR must be a valid color name.  */)
 }
 
 
-/* Load color with name NAME for use by face FACE on frame F.
-   TARGET_INDEX must be one of LFACE_FOREGROUND_INDEX,
-   LFACE_BACKGROUND_INDEX, LFACE_UNDERLINE_INDEX, LFACE_OVERLINE_INDEX,
-   LFACE_STRIKE_THROUGH_INDEX, or LFACE_BOX_INDEX.  Value is the
-   pixel color.  If color cannot be loaded, display a message, and
-   return the foreground, background or underline color of F, but
-   record that fact in flags of the face so that we don't try to free
-   these colors.  */
-
-#ifndef MSDOS
-static
-#endif
-unsigned long
-load_color (struct frame *f, struct face *face, Lisp_Object name,
-	    enum lface_attribute_index target_index)
+static unsigned long
+load_color2 (struct frame *f, struct face *face, Lisp_Object name,
+             enum lface_attribute_index target_index, XColor *color)
 {
-  XColor color;
-
   eassert (STRINGP (name));
   eassert (target_index == LFACE_FOREGROUND_INDEX
 	   || target_index == LFACE_BACKGROUND_INDEX
@@ -1204,7 +1193,7 @@ load_color (struct frame *f, struct face *face, Lisp_Object name,
 
   /* if the color map is full, defined_color will return a best match
      to the values in an existing cell. */
-  if (!defined_color (f, SSDATA (name), &color, 1))
+  if (!defined_color (f, SSDATA (name), color, 1))
     {
       add_to_log ("Unable to load color \"%s\"", name, Qnil);
 
@@ -1212,32 +1201,32 @@ load_color (struct frame *f, struct face *face, Lisp_Object name,
 	{
 	case LFACE_FOREGROUND_INDEX:
 	  face->foreground_defaulted_p = 1;
-	  color.pixel = FRAME_FOREGROUND_PIXEL (f);
+	  color->pixel = FRAME_FOREGROUND_PIXEL (f);
 	  break;
 
 	case LFACE_BACKGROUND_INDEX:
 	  face->background_defaulted_p = 1;
-	  color.pixel = FRAME_BACKGROUND_PIXEL (f);
+	  color->pixel = FRAME_BACKGROUND_PIXEL (f);
 	  break;
 
 	case LFACE_UNDERLINE_INDEX:
 	  face->underline_defaulted_p = 1;
-	  color.pixel = FRAME_FOREGROUND_PIXEL (f);
+	  color->pixel = FRAME_FOREGROUND_PIXEL (f);
 	  break;
 
 	case LFACE_OVERLINE_INDEX:
 	  face->overline_color_defaulted_p = 1;
-	  color.pixel = FRAME_FOREGROUND_PIXEL (f);
+	  color->pixel = FRAME_FOREGROUND_PIXEL (f);
 	  break;
 
 	case LFACE_STRIKE_THROUGH_INDEX:
 	  face->strike_through_color_defaulted_p = 1;
-	  color.pixel = FRAME_FOREGROUND_PIXEL (f);
+	  color->pixel = FRAME_FOREGROUND_PIXEL (f);
 	  break;
 
 	case LFACE_BOX_INDEX:
 	  face->box_color_defaulted_p = 1;
-	  color.pixel = FRAME_FOREGROUND_PIXEL (f);
+	  color->pixel = FRAME_FOREGROUND_PIXEL (f);
 	  break;
 
 	default:
@@ -1249,7 +1238,27 @@ load_color (struct frame *f, struct face *face, Lisp_Object name,
     ++ncolors_allocated;
 #endif
 
-  return color.pixel;
+  return color->pixel;
+}
+
+/* Load color with name NAME for use by face FACE on frame F.
+   TARGET_INDEX must be one of LFACE_FOREGROUND_INDEX,
+   LFACE_BACKGROUND_INDEX, LFACE_UNDERLINE_INDEX, LFACE_OVERLINE_INDEX,
+   LFACE_STRIKE_THROUGH_INDEX, or LFACE_BOX_INDEX.  Value is the
+   pixel color.  If color cannot be loaded, display a message, and
+   return the foreground, background or underline color of F, but
+   record that fact in flags of the face so that we don't try to free
+   these colors.  */
+
+#ifndef MSDOS
+static
+#endif
+unsigned long
+load_color (struct frame *f, struct face *face, Lisp_Object name,
+	    enum lface_attribute_index target_index)
+{
+  XColor color;
+  return load_color2 (f, face, name, target_index, &color);
 }
 
 
@@ -1264,7 +1273,8 @@ static void
 load_face_colors (struct frame *f, struct face *face,
 		  Lisp_Object attrs[LFACE_VECTOR_SIZE])
 {
-  Lisp_Object fg, bg;
+  Lisp_Object fg, bg, dfg;
+  XColor xfg, xbg;
 
   bg = attrs[LFACE_BACKGROUND_INDEX];
   fg = attrs[LFACE_FOREGROUND_INDEX];
@@ -1289,8 +1299,18 @@ load_face_colors (struct frame *f, struct face *face,
       face->stipple = load_pixmap (f, Vface_default_stipple);
     }
 
-  face->background = load_color (f, face, bg, LFACE_BACKGROUND_INDEX);
-  face->foreground = load_color (f, face, fg, LFACE_FOREGROUND_INDEX);
+  face->background = load_color2 (f, face, bg, LFACE_BACKGROUND_INDEX, &xbg);
+  face->foreground = load_color2 (f, face, fg, LFACE_FOREGROUND_INDEX, &xfg);
+
+  dfg = attrs[LFACE_DISTANT_FOREGROUND_INDEX];
+  if (!NILP (dfg) && !UNSPECIFIEDP (dfg)
+      && color_distance (&xbg, &xfg) < NEAR_SAME_COLOR_THRESHOLD)
+    {
+      if (EQ (attrs[LFACE_INVERSE_INDEX], Qt))
+        face->background = load_color (f, face, dfg, LFACE_BACKGROUND_INDEX);
+      else
+        face->foreground = load_color (f, face, dfg, LFACE_FOREGROUND_INDEX);
+    }
 }
 
 #ifdef HAVE_X_WINDOWS
@@ -1721,6 +1741,8 @@ the WIDTH times as wide as FACE on FRAME.  */)
 #define LFACE_FONT(LFACE)	    AREF ((LFACE), LFACE_FONT_INDEX)
 #define LFACE_INHERIT(LFACE)	    AREF ((LFACE), LFACE_INHERIT_INDEX)
 #define LFACE_FONTSET(LFACE)	    AREF ((LFACE), LFACE_FONTSET_INDEX)
+#define LFACE_DISTANT_FOREGROUND(LFACE) \
+  AREF ((LFACE), LFACE_DISTANT_FOREGROUND_INDEX)
 
 /* Non-zero if LFACE is a Lisp face.  A Lisp face is a vector of size
    LFACE_VECTOR_SIZE which has the symbol `face' in slot 0.  */
@@ -2449,6 +2471,13 @@ merge_face_ref (struct frame *f, Lisp_Object face_ref, Lisp_Object *to,
 		  else
 		    err = 1;
 		}
+	      else if (EQ (keyword, QCdistant_foreground))
+		{
+		  if (STRINGP (value))
+		    to[LFACE_DISTANT_FOREGROUND_INDEX] = value;
+		  else
+		    err = 1;
+		}
 	      else if (EQ (keyword, QCbackground))
 		{
 		  if (STRINGP (value))
@@ -3005,6 +3034,23 @@ FRAME 0 means change the face on all frames, and change the default
       old_value = LFACE_FOREGROUND (lface);
       ASET (lface, LFACE_FOREGROUND_INDEX, value);
     }
+  else if (EQ (attr, QCdistant_foreground))
+    {
+      /* Compatibility with 20.x.  */
+      if (NILP (value))
+	value = Qunspecified;
+      if (!UNSPECIFIEDP (value) && !IGNORE_DEFFACE_P (value))
+	{
+	  /* Don't check for valid color names here because it depends
+	     on the frame (display) whether the color will be valid
+	     when the face is realized.  */
+	  CHECK_STRING (value);
+	  if (SCHARS (value) == 0)
+	    signal_error ("Empty distant-foreground color value", value);
+	}
+      old_value = LFACE_DISTANT_FOREGROUND (lface);
+      ASET (lface, LFACE_DISTANT_FOREGROUND_INDEX, value);
+    }
   else if (EQ (attr, QCbackground))
     {
       /* Compatibility with 20.x.  */
@@ -3649,6 +3695,8 @@ frames).  If FRAME is omitted or nil, use the selected frame.  */)
     value = LFACE_INVERSE (lface);
   else if (EQ (keyword, QCforeground))
     value = LFACE_FOREGROUND (lface);
+  else if (EQ (keyword, QCdistant_foreground))
+    value = LFACE_DISTANT_FOREGROUND (lface);
   else if (EQ (keyword, QCbackground))
     value = LFACE_BACKGROUND (lface);
   else if (EQ (keyword, QCstipple))
@@ -4688,6 +4736,9 @@ x_supports_face_attributes_p (struct frame *f,
       || (!UNSPECIFIEDP (attrs[LFACE_FOREGROUND_INDEX])
 	  && face_attr_equal_p (attrs[LFACE_FOREGROUND_INDEX],
 				def_attrs[LFACE_FOREGROUND_INDEX]))
+      || (!UNSPECIFIEDP (attrs[LFACE_DISTANT_FOREGROUND_INDEX])
+	  && face_attr_equal_p (attrs[LFACE_DISTANT_FOREGROUND_INDEX],
+				def_attrs[LFACE_DISTANT_FOREGROUND_INDEX]))
       || (!UNSPECIFIEDP (attrs[LFACE_BACKGROUND_INDEX])
 	  && face_attr_equal_p (attrs[LFACE_BACKGROUND_INDEX],
 				def_attrs[LFACE_BACKGROUND_INDEX]))
@@ -6361,6 +6412,7 @@ syms_of_xfaces (void)
   DEFSYM (QCwidth, ":width");
   DEFSYM (QCfont, ":font");
   DEFSYM (QCfontset, ":fontset");
+  DEFSYM (QCdistant_foreground, ":distant-foreground");
   DEFSYM (QCbold, ":bold");
   DEFSYM (QCitalic, ":italic");
   DEFSYM (QCoverline, ":overline");