fill-rule.c

按照官方的说法：Cairo is a vector graphics library with cross-device output support. 翻译过来

/*
 * Copyright © 2004 Red Hat, Inc.
 *
 * Permission to use, copy, modify, distribute, and sell this software
 * and its documentation for any purpose is hereby granted without
 * fee, provided that the above copyright notice appear in all copies
 * and that both that copyright notice and this permission notice
 * appear in supporting documentation, and that the name of
 * Red Hat, Inc. not be used in advertising or publicity pertaining to
 * distribution of the software without specific, written prior
 * permission. Red Hat, Inc. makes no representations about the
 * suitability of this software for any purpose.  It is provided "as
 * is" without express or implied warranty.
 *
 * RED HAT, INC. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
 * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS, IN NO EVENT SHALL RED HAT, INC. BE LIABLE FOR ANY SPECIAL,
 * INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
 * RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
 * IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Author: Carl D. Worth <[e-mail]>
 */

/* Bug history
 *
 * 2004-10-27  Carl Worth  <[e-mail]>
 *
 *   There's currently a regression bug in the tessellation code. This
 *   causes each of these simple star shapes to be filled incorrectly.
 *
 *   It looks like right now we can get this test to pass by doing:
 *
 *       cvs update -r 1.16 src/cairo_traps.c
 *
 *   But we don't want to revert that change permanently since it
 *   really does correct some bugs. It must be that the old version of
 *   the code is masking some other bugs in the tessellation code. My
 *   current plan is to back this revision up for the next snapshot,
 *   but not to list the test as an expected failure since I'm
 *   planning on doing the new tessellator which should fix this
 *   problem.
 *
 * 2005-01-11 Carl Worth <[e-mail]>
 *
 *   Keith committed some fixes that fix the original size-20
 *   star_path:
 *
 * 	* src/cairo_wideint.c: (_cairo_int32x32_64_mul),
 *	(_cairo_int64x64_128_mul):
 *	* src/cairo_wideint.h:
 *	int32x32_64_mul and int64x64_128_mul are different from their
 *	unsigned compatriots
 *
 * 2005-01-12 Carl Worth <[e-mail]>
 *
 *   Going back to the SVG test suite, however, the original star
 *   shape is still broken. Adding both shapes now as little_star_path
 *   and big_star_path.
 *
 */

#include "cairo-test.h"

#define LITTLE_STAR_SIZE 20
#define BIG_STAR_SIZE    80

cairo_test_t test = {
    "fill-rule",
    "Tests cairo_set_full_rule with some star shapes",
    BIG_STAR_SIZE * 2 + 3, BIG_STAR_SIZE + LITTLE_STAR_SIZE + 3
};

/* The SVG start trimmed down, but still showing the bug (originally) */
static void
little_star_path (cairo_t *cr)
{
    cairo_move_to (cr, 10, 0);
    cairo_rel_line_to (cr, 6, 20);
    cairo_rel_line_to (cr, -16, -12);
    cairo_rel_line_to (cr, 20, 0);
    cairo_rel_line_to (cr, -16, 12);
}

/* The star shape from the SVG test suite. This was is still buggy even after
   we got little_star_path working. */
static void
big_star_path (cairo_t *cr)
{
    cairo_move_to (cr, 40, 0);
    cairo_rel_line_to (cr, 25, 80);
    cairo_rel_line_to (cr, -65, -50);
    cairo_rel_line_to (cr, 80, 0);
    cairo_rel_line_to (cr, -65, 50);
    cairo_close_path (cr);
}

/* Fill the same path twice, once with each fill rule */
static cairo_test_status_t
draw (cairo_t *cr, int width, int height)
{
    cairo_set_source_rgb (cr, 1, 0, 0);

    cairo_translate (cr, 1, 1);
    little_star_path (cr);
    cairo_set_fill_rule (cr, CAIRO_FILL_RULE_WINDING);
    cairo_fill (cr);

    cairo_translate (cr, LITTLE_STAR_SIZE + 1, 0);
    little_star_path (cr);
    cairo_set_fill_rule (cr, CAIRO_FILL_RULE_EVEN_ODD);
    cairo_fill (cr);

    cairo_translate (cr, -(LITTLE_STAR_SIZE + 1), LITTLE_STAR_SIZE + 1);
    big_star_path (cr);
    cairo_set_fill_rule (cr, CAIRO_FILL_RULE_WINDING);
    cairo_fill (cr);

    cairo_translate (cr, BIG_STAR_SIZE + 1, 0);
    big_star_path (cr);
    cairo_set_fill_rule (cr, CAIRO_FILL_RULE_EVEN_ODD);
    cairo_fill (cr);

    return CAIRO_TEST_SUCCESS;
}

int
main (void)
{
    return cairo_test (&test, draw);
}