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/*
* Copyright © 2005 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 <cworth@cworth.org>
*/
/* Bug history
*
* 2005-06-01 Carl Worth <cworth@cworth.org>
*
* There's a long-standing bug in that self-intersecting paths give
* an incorrect result when stroked. The problem is that the
* trapezoids are generated incrementally along the stroke and as
* such, are not disjoint. The errant intersections of these
* trapezoids then leads to overfilled pixels.
*
* The test belows first creates and fills a path. Then it creates a
* second path which has a stroked boundary identical to the first
* filled path. But the results of the two operations are
* different. The most obvious difference is in the central region
* where the entire path intersects itself. But notice that every
* time the path turns there are also errors on the inside of the
* turn, (since the subsequent trapezoids along the path intersect).
*/
#include "cairo-test.h"
cairo_test_t test = {
"self-intersecting",
"Test strokes of self-intersecting paths",
10, 20
};
static cairo_test_status_t
draw (cairo_t *cr, int width, int height)
{
cairo_translate (cr, 1.0, 1.0);
cairo_set_source_rgb (cr, 1, 0, 0); /* red */
/* First draw the desired shape with a fill */
cairo_rectangle (cr, 0.5, 0.5, 4.0, 4.0);
cairo_rectangle (cr, 3.5, 3.5, 4.0, 4.0);
cairo_rectangle (cr, 3.5, 1.5, -2.0, 2.0);
cairo_rectangle (cr, 6.5, 4.5, -2.0, 2.0);
cairo_fill (cr);
/* Then try the same thing with a stroke */
cairo_translate (cr, 0, 10);
cairo_move_to (cr, 1.0, 1.0);
cairo_rel_line_to (cr, 3.0, 0.0);
cairo_rel_line_to (cr, 0.0, 6.0);
cairo_rel_line_to (cr, 3.0, 0.0);
cairo_rel_line_to (cr, 0.0, -3.0);
cairo_rel_line_to (cr, -6.0, 0.0);
cairo_close_path (cr);
cairo_set_line_width (cr, 1.0);
cairo_stroke (cr);
return CAIRO_TEST_SUCCESS;
}
int
main (void)
{
return cairo_test_expect_failure (&test, draw,
"Self-intersecting strokes are wrong due to incremental trapezoidization.");
}
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