cairo_set_line_width (cr, 30.0);
cairo_set_line_cap (cr, CAIRO_LINE_CAP_BUTT); /* default */
cairo_move_to (cr, 64.0, 50.0); cairo_line_to (cr, 64.0, 200.0);
cairo_stroke (cr);
cairo_set_line_cap (cr, CAIRO_LINE_CAP_ROUND);
cairo_move_to (cr, 128.0, 50.0); cairo_line_to (cr, 128.0, 200.0);
cairo_stroke (cr);
cairo_set_line_cap (cr, CAIRO_LINE_CAP_SQUARE);
cairo_move_to (cr, 192.0, 50.0); cairo_line_to (cr, 192.0, 200.0);
cairo_stroke (cr);
/* draw helping lines */
cairo_set_source_rgb (cr, 1, 0.2, 0.2);
cairo_set_line_width (cr, 2.56);
cairo_move_to (cr, 64.0, 50.0); cairo_line_to (cr, 64.0, 200.0);
cairo_move_to (cr, 128.0, 50.0); cairo_line_to (cr, 128.0, 200.0);
cairo_move_to (cr, 192.0, 50.0); cairo_line_to (cr, 192.0, 200.0);
cairo_stroke (cr);
