client: add generic display function for table rows

There was no easy to use API for printing the contents of a table, and
was left up to the caller to handle manually. This adds display_table_row
which makes displaying tables much easier, including automatic support
for line truncation and continuation on the next line.

Lines which are too long will be truncated and displayed on the next
line while also taking into account any colored output. This works with any
number of columns.

This removes the need for the module to play games with encoding newlines
and tabs to make the output look nice.

As a start, this functionality was added to the command display.

client/display.c

@@ -376,8 +376,183 @@ void display_table_footer(void)
 	display_refresh_check_applicability();
 }
 
-void display_command_line(const char *command_family,
-						const struct command *cmd)
+static unsigned int color_end(char *s)
+{
+	char *start = s;
+
+	while (*s != 'm' && *s != '\0')
+		s++;
+
+	return s - start + 1;
+}
+
+/*
+ * Finds last space in 's' before 'max' characters, terminates at that index,
+ * and returns a new string to be printed on the next line.
+ *
+ * 'max' should be set to the column width, but is also an out parameter since
+ * this width can be updated if colored escapes are detected.
+ *
+ * Any colored escapes found are set to 'color_out' so they can be re-enabled
+ * on the next line.
+ */
+static char* next_line(char *s, unsigned int *max, char **color_out)
+{
+	unsigned int i;
+	int last_space = -1;
+	int last_color = -1;
+
+	/* Find the last space before 'max', as well as any color */
+	for (i = 0; i <= *max && s[i] != '\0'; i++) {
+		if (s[i] == ' ')
+			last_space = i;
+		else if (s[i] == 0x1b) {
+			/* color escape won't count for column width */
+			*max += color_end(s + i);
+			last_color = i;
+		}
+	}
+
+	/* Reached the end of the string within the column bounds */
+	if (i <= *max)
+		return NULL;
+
+	/* Not anywhere nice to split the line */
+	if (last_space == -1)
+		last_space = *max - 1;
+
+	/*
+	 * Only set the color if it occurred prior to the last space. If after,
+	 * it will get picked up on the next line.
+	 */
+	if (last_color != -1 && last_space >= last_color)
+		*color_out = l_strndup(s + last_color,
+					color_end(s + last_color));
+	else
+		*color_out = NULL;
+
+	s[last_space] = '\0';
+
+	return l_strdup(s + last_space + 1);
+}
+
+struct table_entry {
+	unsigned int width;
+	char *next;
+	char *color;
+};
+
+/*
+ * Appends the next line from 'e' to 'line_buf'. 'done' is only set false when
+ * there are more lines needed for the current entry.
+ */
+static int entry_append(struct table_entry *e, char *line_buf)
+{
+	char *value = e->next;
+	unsigned int ret = 0;
+	unsigned int width = e->width;
+
+	/* Empty line */
+	if (!value)
+		return sprintf(line_buf, "%-*s  ", e->width, "");
+
+	/* Color from previous line */
+	if (e->color) {
+		ret = sprintf(line_buf, "%s", e->color);
+		l_free(e->color);
+		e->color = NULL;
+	}
+
+	/* Advance entry to next line, and terminate current */
+	e->next = next_line(value, &width, &e->color);
+
+	/* Append current line */
+	ret += sprintf(line_buf + ret, "%-*s  ", width, value);
+
+	l_free(value);
+
+	/* Un-color output for next column */
+	if (e->color)
+		ret += sprintf(line_buf + ret, "%s", COLOR_OFF);
+
+	return ret;
+}
+
+static bool entries_done(unsigned int num, struct table_entry *e)
+{
+	unsigned int i;
+
+	for (i = 0; i < num; i++)
+		if (e[i].next)
+			return false;
+
+	return true;
+}
+
+/*
+ * Expects an initial margin, number of columns in table, then row data:
+ *
+ * <row width>, <row data>, ...
+ *
+ * The data string can be of any length, and will be split into new lines of
+ * length <row width>.
+ */
+void display_table_row(const char *margin, unsigned int ncolumns, ...)
+{
+	char buf[512];
+	char *str = buf;
+	unsigned int i;
+	struct table_entry entries[ncolumns];
+	va_list va;
+
+	memset(&entries[0], 0, sizeof(entries));
+
+	va_start(va, ncolumns);
+
+	str += sprintf(str, "%s", margin);
+
+	for (i = 0; i < ncolumns; i++) {
+		struct table_entry *e = &entries[i];
+
+		e->width = va_arg(va, unsigned int);
+		e->next = l_strdup(va_arg(va, char*));
+
+		str += entry_append(e, str);
+	}
+
+	va_end(va);
+
+	display("%s\n", buf);
+	str = buf;
+
+	/*
+	 * The first column should now be indented, which effects the entry
+	 * width. Subtract this indentation only from the first column.
+	 */
+	entries[0].width -= strlen(margin) * 2;
+
+	while (!entries_done(ncolumns, &entries[0])) {
+		for (i = 0; i < ncolumns; i++) {
+			struct table_entry *e = &entries[i];
+
+			if (i == 0)
+				str += sprintf(str, "%s%s%s", margin,
+						margin, margin);
+
+			str += entry_append(e, str);
+		}
+
+		display("%s\n", buf);
+		str = buf;
+	}
+
+	for (i = 0; i < ncolumns; i++) {
+		if (entries[i].color)
+			l_free(entries[i].color);
+	}
+}
+
+void display_command_line(const char *command_family, const struct command *cmd)
 {
 	char *cmd_line = l_strdup_printf("%s%s%s%s%s%s%s",
 				command_family ? : "",
@@ -388,7 +563,7 @@ void display_command_line(const char *command_family,
 				cmd->arg ? " " : "",
 				cmd->arg ? : "");
 
-	display(MARGIN "%-*s%s\n", 50, cmd_line, cmd->desc ? : "");
+	display_table_row(MARGIN, 2, 50, cmd_line, 30, cmd->desc);
 
 	l_free(cmd_line);
 }

client/display.h

@@ -37,6 +37,7 @@ void display(const char *format, ...)
 		__attribute__((format(printf, 1, 2)));
 void display_table_header(const char *caption, const char *fmt, ...)
 		__attribute__((format(printf, 2, 3)));
+void display_table_row(const char *margin, unsigned int ncolumns, ...);
 void display_table_footer(void);
 void display_error(const char *error);
 void display_command_line(const char *command_family,