void xr_draw_chart (const struct chart_item *, cairo_t *,
double width, double height);
+cairo_surface_t *xr_draw_image_chart (const struct chart_item *,
+ const struct cell_color *fg,
+ const struct cell_color *bg);
+char *xr_write_png_image (cairo_surface_t *,
+ const char *file_name_template, int number);
+
char *xr_draw_png_chart (const struct chart_item *,
const char *file_name_template, int number,
const struct cell_color *fg,