Enable custom schemes for column colors in the graph API

Currently, the graph code is hardcoded to use ANSI color escapes for
coloring the column characters in the generated graphs. This patch
allows a custom scheme of colors to be set at runtime, allowing
different types of color escapes to be used.

A new function - graph_set_column_colors() - is added to the graph.h API,
which allows a custom column_colors array (and column_colors_max value)
to replace the builtin ANSI array (and _max value). The new function -
if used - must be called before graph_init() is called.

Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 26 insertions, 11 deletions

diff --git a/graph.c b/graph.c
index 47397daca3..e2a58605ca 100644
--- a/graph.c
+++ b/graph.c
@@ -62,7 +62,7 @@ enum graph_state {
 /*
  * The list of available column colors.
  */
-static char column_colors[][COLOR_MAXLEN] = {
+static const char *column_colors_ansi[] = {
 	GIT_COLOR_RED,
 	GIT_COLOR_GREEN,
 	GIT_COLOR_YELLOW,
@@ -75,23 +75,33 @@ static char column_colors[][COLOR_MAXLEN] = {
 	GIT_COLOR_BOLD_BLUE,
 	GIT_COLOR_BOLD_MAGENTA,
 	GIT_COLOR_BOLD_CYAN,
+	GIT_COLOR_RESET,
 };
 
-#define COLUMN_COLORS_MAX (ARRAY_SIZE(column_colors))
+#define COLUMN_COLORS_ANSI_MAX (ARRAY_SIZE(column_colors_ansi) - 1)
 
-static const char *column_get_color_code(const struct column *c)
+static const char **column_colors;
+static unsigned short column_colors_max;
+
+void graph_set_column_colors(const char **colors, unsigned short colors_max)
+{
+	column_colors = colors;
+	column_colors_max = colors_max;
+}
+
+static const char *column_get_color_code(unsigned short color)
 {
-	return column_colors[c->color];
+	return column_colors[color];
 }
 
 static void strbuf_write_column(struct strbuf *sb, const struct column *c,
 				char col_char)
 {
-	if (c->color < COLUMN_COLORS_MAX)
-		strbuf_addstr(sb, column_get_color_code(c));
+	if (c->color < column_colors_max)
+		strbuf_addstr(sb, column_get_color_code(c->color));
 	strbuf_addch(sb, col_char);
-	if (c->color < COLUMN_COLORS_MAX)
-		strbuf_addstr(sb, GIT_COLOR_RESET);
+	if (c->color < column_colors_max)
+		strbuf_addstr(sb, column_get_color_code(column_colors_max));
 }
 
 struct git_graph {
@@ -215,6 +225,11 @@ static struct strbuf *diff_output_prefix_callback(struct diff_options *opt, void
 struct git_graph *graph_init(struct rev_info *opt)
 {
 	struct git_graph *graph = xmalloc(sizeof(struct git_graph));
+
+	if (!column_colors)
+		graph_set_column_colors(column_colors_ansi,
+					COLUMN_COLORS_ANSI_MAX);
+
 	graph->commit = NULL;
 	graph->revs = opt;
 	graph->num_parents = 0;
@@ -231,7 +246,7 @@ struct git_graph *graph_init(struct rev_info *opt)
 	 * always increment it for the first commit we output.
 	 * This way we start at 0 for the first commit.
 	 */
-	graph->default_column_color = COLUMN_COLORS_MAX - 1;
+	graph->default_column_color = column_colors_max - 1;
 
 	/*
 	 * Allocate a reasonably large default number of columns
@@ -354,7 +369,7 @@ static struct commit_list *first_interesting_parent(struct git_graph *graph)
 static unsigned short graph_get_current_column_color(const struct git_graph *graph)
 {
 	if (!DIFF_OPT_TST(&graph->revs->diffopt, COLOR_DIFF))
-		return COLUMN_COLORS_MAX;
+		return column_colors_max;
 	return graph->default_column_color;
 }
 
@@ -364,7 +379,7 @@ static unsigned short graph_get_current_column_color(const struct git_graph *gra
 static void graph_increment_column_color(struct git_graph *graph)
 {
 	graph->default_column_color = (graph->default_column_color + 1) %
-		COLUMN_COLORS_MAX;
+		column_colors_max;
 }
 
 static unsigned short graph_find_commit_color(const struct git_graph *graph,