[PATCH] perf diff: Introduce the new rules of colored printing of delta.

[SeongSoo Cho <nexusz99@gmail.com>]

From: SeongSoo Cho <nexusz99@gmail.com>

As you know, there are the common colored printing of percents so overhead(%) can be c$
But Delta means difference percents from percents of overhead between two files e.g. p$
Although the rule is for overhead(%), Delta value also follow the same rule.

So, I think that it would be better to use the new colored rule for the Delta as below.

Increament: background colored in red (e.g. +0.50%)
Decrement: colored in blue (e.g. -5.50%)
Same: default color (e.g. +0.00%)

Instead of percent_color_snprintf() function, use new delta_color_snprintf() function.

Signed-off-by: SeongSoo Cho <nexusz99@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Taeung Song <taeung@kosslab.kr>
---
 tools/perf/builtin-diff.c |  2 +-
 tools/perf/util/color.c   | 21 +++++++++++++++++++++
 tools/perf/util/color.h   |  1 +
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-diff.c b/tools/perf/builtin-diff.c
index 9ff0db4..228bad1 100644
--- a/tools/perf/builtin-diff.c
+++ b/tools/perf/builtin-diff.c
@@ -868,7 +868,7 @@ static int __hpp__color_compare(struct perf_hpp_fmt *fmt,
 			diff = compute_delta(he, pair);
 
 		scnprintf(pfmt, 20, "%%%+d.2f%%%%", dfmt->header_width - 1);
-		return percent_color_snprintf(hpp->buf, hpp->size,
+		return delta_color_snprintf(hpp->buf, hpp->size,
 					pfmt, diff);
 	case COMPUTE_RATIO:
 		if (he->dummy)
diff --git a/tools/perf/util/color.c b/tools/perf/util/color.c
index dbbf89b..643e932 100644
--- a/tools/perf/util/color.c
+++ b/tools/perf/util/color.c
@@ -219,3 +219,24 @@ int percent_color_len_snprintf(char *bf, size_t size, const char *fmt, ...)
 	color = get_percent_color(percent);
 	return color_snprintf(bf, size, color, fmt, len, percent);
 }
+
+int delta_color_snprintf(char *bf, size_t size, const char *fmt, ...)
+{
+	va_list args;
+	double diff, percent;
+	const char *color = PERF_COLOR_NORMAL;
+
+	va_start(args, fmt);
+	diff = va_arg(args, double);
+	va_end(args);
+
+	/* diff command printed second digit after the decimal point. */
+	percent = roundf(diff * 100) / 100;
+	if (percent < 0)
+		color = PERF_COLOR_BLUE;
+	else {
+		if (percent > 0)
+			color = PERF_COLOR_BG_RED;
+	}
+	return color_snprintf(bf, size, color, fmt, diff);
+}
diff --git a/tools/perf/util/color.h b/tools/perf/util/color.h
index a93997f..608edc9 100644
--- a/tools/perf/util/color.h
+++ b/tools/perf/util/color.h
@@ -40,6 +40,7 @@ int value_color_snprintf(char *bf, size_t size, const char *fmt, double value);
 int percent_color_snprintf(char *bf, size_t size, const char *fmt, ...);
 int percent_color_len_snprintf(char *bf, size_t size, const char *fmt, ...);
 int percent_color_fprintf(FILE *fp, const char *fmt, double percent);
+int delta_color_snprintf(char *bf, size_t size, const char *fmt, ...);
 const char *get_percent_color(double percent);
 
 #endif /* __PERF_COLOR_H */
-- 
2.7.4