Improve the Help tab

There are now up to three bindings per action by default, so grouping
is desirable.  We can even follow the more or less logical order given
by enumeration values.

It should be much easier to find what you need.

nncmpp.c

@@ -3030,40 +3030,72 @@ info_tab_init (void)
 
 // --- Help tab ----------------------------------------------------------------
 
+static struct strv g_help_tab_lines;
+
+static size_t
+help_tab_strfkey (const termo_key_t *key, char *buf, size_t len)
+{
+	// For display purposes, this is highly desirable
+	int flags = termo_get_flags (g.tk);
+	termo_set_flags (g.tk, flags | TERMO_FLAG_SPACESYMBOL);
+	termo_key_t fixed = *key;
+	termo_canonicalise (g.tk, &fixed);
+	termo_set_flags (g.tk, flags);
+	return termo_strfkey_utf8 (g.tk, buf, len, &fixed, TERMO_FORMAT_ALTISMETA);
+}
+
+static void
+help_tab_group (struct binding *keys, size_t len, struct strv *out)
+{
+	char buf[16];
+	for (enum action i = 0; i < ACTION_COUNT; i++)
+	{
+		struct strv ass = strv_make ();
+		for (size_t k = 0; k < len; k++)
+		{
+			if (keys[k].action != i)
+				continue;
+			help_tab_strfkey (&keys[k].decoded, buf, sizeof buf);
+			strv_append (&ass, buf);
+		}
+		if (ass.len)
+		{
+			char *joined = strv_join (&ass, ", ");
+			strv_append_owned (out, xstrdup_printf
+				("  %-30s %s", g_actions[i].description, joined));
+			free (joined);
+		}
+		strv_free (&ass);
+	}
+}
+
 static void
 help_tab_on_item_draw (size_t item_index, struct row_buffer *buffer, int width)
 {
 	(void) width;
 
-	// TODO: group them the other way around for clarity
+	hard_assert (item_index < g_help_tab_lines.len);
-	//   - go through 0..ACTION_COUNT
+	const char *line = g_help_tab_lines.vector[item_index];
-	//   - ...
+	row_buffer_append (buffer, line, *line == ' ' ? 0 : A_BOLD);
-
-	hard_assert (item_index < g_normal_keys_len);
-	struct binding *binding = &g_normal_keys[item_index];
-
-	// For display purposes, this is highly desirable
-	int flags = termo_get_flags (g.tk);
-	termo_set_flags (g.tk, flags | TERMO_FLAG_SPACESYMBOL);
-	termo_key_t key = binding->decoded;
-	termo_canonicalise (g.tk, &key);
-	termo_set_flags (g.tk, flags);
-
-	char buf[16];
-	termo_strfkey_utf8 (g.tk, buf, sizeof buf, &key, TERMO_FORMAT_ALTISMETA);
-	char *text = xstrdup_printf ("%-12s %s",
-		buf, g_actions[binding->action].description);
-	row_buffer_append (buffer, text, 0);
-	free (text);
 }
 
 static struct tab *
 help_tab_init (void)
 {
+	g_help_tab_lines = strv_make ();
+
+	strv_append (&g_help_tab_lines, "Normal mode actions");
+	help_tab_group (g_normal_keys, g_normal_keys_len, &g_help_tab_lines);
+	strv_append (&g_help_tab_lines, "");
+
+	strv_append (&g_help_tab_lines, "Editor mode actions");
+	help_tab_group (g_editor_keys, g_editor_keys_len, &g_help_tab_lines);
+	strv_append (&g_help_tab_lines, "");
+
 	static struct tab super;
 	tab_init (&super, "Help");
 	super.on_item_draw = help_tab_on_item_draw;
-	super.item_count = g_normal_keys_len;
+	super.item_count = g_help_tab_lines.len;
 	return &super;
 }