netdev - [iproute PATCH v2 1/1] color: use "light" colors for dark background

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Date:   Mon, 27 Feb 2017 10:55:27 +0100
From:   Petr Vorel <pvorel@...e.cz>
To:     netdev@...r.kernel.org
Cc:     Petr Vorel <pvorel@...e.cz>, Mathias Nyman <m.nyman@....fi>,
        Yegor Yefremov <yegorslists@...glemail.com>
Subject: [iproute PATCH v2 1/1] color: use "light" colors for dark background

COLORFGBG environment variable is used to detect dark background.

Idea and a bit of code is borrowed from Vim, thanks.

Signed-off-by: Petr Vorel <pvorel@...e.cz>
---
Changes v1->V2:
* Rename function and enum values
* Add missing bold white enum + it's code.
---
 include/color.h |  1 +
 lib/color.c     | 45 ++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/include/color.h b/include/color.h
index c1c29831..ba0b237e 100644
--- a/include/color.h
+++ b/include/color.h
@@ -12,6 +12,7 @@ enum color_attr {
 };
 
 void enable_color(void);
+void set_color_palette(void);
 int color_fprintf(FILE *fp, enum color_attr attr, const char *fmt, ...);
 enum color_attr ifa_family_color(__u8 ifa_family);
 enum color_attr oper_state_color(__u8 state);
diff --git a/lib/color.c b/lib/color.c
index 95596be2..c048c76e 100644
--- a/lib/color.c
+++ b/lib/color.c
@@ -1,5 +1,7 @@
 #include <stdio.h>
 #include <stdarg.h>
+#include <stdlib.h>
+#include <string.h>
 #include <sys/socket.h>
 #include <sys/types.h>
 #include <linux/if.h>
@@ -14,6 +16,13 @@ enum color {
 	C_MAGENTA,
 	C_CYAN,
 	C_WHITE,
+	C_BOLD_RED,
+	C_BOLD_GREEN,
+	C_BOLD_YELLOW,
+	C_BOLD_BLUE,
+	C_BOLD_MAGENTA,
+	C_BOLD_CYAN,
+	C_BOLD_WHITE,
 	C_CLEAR
 };
 
@@ -25,25 +34,59 @@ static const char * const color_codes[] = {
 	"\e[35m",
 	"\e[36m",
 	"\e[37m",
+	"\e[1;31m",
+	"\e[1;32m",
+	"\e[1;33m",
+	"\e[1;34m",
+	"\e[1;35m",
+	"\e[1;36m",
+	"\e[1;37m",
 	"\e[0m",
 	NULL,
 };
 
 static enum color attr_colors[] = {
+	/* light background */
 	C_CYAN,
 	C_YELLOW,
 	C_MAGENTA,
 	C_BLUE,
 	C_GREEN,
 	C_RED,
+	C_CLEAR,
+
+	/* dark background */
+	C_BOLD_CYAN,
+	C_BOLD_YELLOW,
+	C_BOLD_MAGENTA,
+	C_BOLD_BLUE,
+	C_BOLD_GREEN,
+	C_BOLD_RED,
 	C_CLEAR
 };
 
+static int is_dark_bg;
 static int color_is_enabled;
 
 void enable_color(void)
 {
 	color_is_enabled = 1;
+	set_color_palette();
+}
+
+void set_color_palette(void)
+{
+	char *p = getenv("COLORFGBG");
+
+	/*
+	 * COLORFGBG environment variable usually contains either two or three
+	 * values separated by semicolons; we want the last value in either case.
+	 * If this value is 0-6 or 8, background is dark.
+	 */
+	if (p && (p = (char *)strrchr(p, ';')) != NULL
+		&& ((p[1] >= '0' && p[1] <= '6') || p[1] == '8')
+		&& p[2] == '\0')
+		is_dark_bg = 1;
 }
 
 int color_fprintf(FILE *fp, enum color_attr attr, const char *fmt, ...)
@@ -58,7 +101,7 @@ int color_fprintf(FILE *fp, enum color_attr attr, const char *fmt, ...)
 		goto end;
 	}
 
-	ret += fprintf(fp, "%s", color_codes[attr_colors[attr]]);
+	ret += fprintf(fp, "%s", color_codes[attr_colors[is_dark_bg ? attr + 7 : attr]]);
 	ret += vfprintf(fp, fmt, args);
 	ret += fprintf(fp, "%s", color_codes[C_CLEAR]);
 
-- 
2.11.0