double xmin, ymin, xmax, ymax;

snippet_normalize (cr, width, height);

cairo_set_line_width(cr, 0.22);

#define LINE(cap) \
  cairo_new_path(cr); \
  cairo_set_line_cap(cr, cap); \
  cairo_move_to(cr, 0.3, 0.3); \
  cairo_line_to(cr, 0.7, 0.3);

#define EXTENT(mesg) \
  cairo_stroke_extents(cr, &xmin, &ymin, &xmax, &ymax); \
  fprintf(stderr, mesg ": %f %f  %f %f\n", xmin, ymin, xmax, ymax);

LINE(CAIRO_LINE_CAP_BUTT)
EXTENT("butt  ")

LINE(CAIRO_LINE_CAP_ROUND)
EXTENT("round ")

LINE(CAIRO_LINE_CAP_SQUARE)
EXTENT("square")