parse_color: support 24-bit RGB values

Some terminals (like XTerm) allow full 24-bit RGB color
specifications using an extension to the regular ANSI color
scheme. Let's allow users to specify hex RGB colors,
enabling the all-important feature of hot pink ref
decorations:

  git log --format="%h%C(#ff69b4)%d%C(reset) %s"

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 28 insertions, 1 deletions

diff --git a/color.c b/color.c
index 3afda9d9dc..ae68792923 100644
--- a/color.c
+++ b/color.c
@@ -32,10 +32,13 @@ struct color {
 		COLOR_UNSPECIFIED = 0,
 		COLOR_NORMAL,
 		COLOR_ANSI, /* basic 0-7 ANSI colors */
-		COLOR_256
+		COLOR_256,
+		COLOR_RGB
 	} type;
 	/* The numeric value for ANSI and 256-color modes */
 	unsigned char value;
+	/* 24-bit RGB color values */
+	unsigned char red, green, blue;
 };
 
 /*
@@ -47,6 +50,16 @@ static int match_word(const char *word, int len, const char *match)
 	return !strncasecmp(word, match, len) && !match[len];
 }
 
+static int get_hex_color(const char *in, unsigned char *out)
+{
+	unsigned int val;
+	val = (hexval(in[0]) << 4) | hexval(in[1]);
+	if (val & ~0xff)
+		return -1;
+	*out = val;
+	return 0;
+}
+
 static int parse_color(struct color *out, const char *name, int len)
 {
 	/* Positions in array must match ANSI color codes */
@@ -64,6 +77,16 @@ static int parse_color(struct color *out, const char *name, int len)
 		return 0;
 	}
 
+	/* Try a 24-bit RGB value */
+	if (len == 7 && name[0] == '#') {
+		if (!get_hex_color(name + 1, &out->red) &&
+		    !get_hex_color(name + 3, &out->green) &&
+		    !get_hex_color(name + 5, &out->blue)) {
+			out->type = COLOR_RGB;
+			return 0;
+		}
+	}
+
 	/* Then pick from our human-readable color names... */
 	for (i = 0; i < ARRAY_SIZE(color_names); i++) {
 		if (match_word(name, len, color_names[i])) {
@@ -140,6 +163,10 @@ static char *color_output(char *out, const struct color *c, char type)
 	case COLOR_256:
 		out += sprintf(out, "%c8;5;%d", type, c->value);
 		break;
+	case COLOR_RGB:
+		out += sprintf(out, "%c8;2;%d;%d;%d", type,
+			       c->red, c->green, c->blue);
+		break;
 	}
 	return out;
 }