Grcov report - self-intersecting.c

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/*

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 * Copyright © 2005 Red Hat, Inc.

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 * Permission to use, copy, modify, distribute, and sell this software

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 * and its documentation for any purpose is hereby granted without

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 * fee, provided that the above copyright notice appear in all copies

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 * and that both that copyright notice and this permission notice

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 * appear in supporting documentation, and that the name of

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 * Red Hat, Inc. not be used in advertising or publicity pertaining to

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 * distribution of the software without specific, written prior

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 * permission. Red Hat, Inc. makes no representations about the

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 * suitability of this software for any purpose.  It is provided "as

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 * is" without express or implied warranty.

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 * RED HAT, INC. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS

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 * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND

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 * FITNESS, IN NO EVENT SHALL RED HAT, INC. BE LIABLE FOR ANY SPECIAL,

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 * INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER

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 * RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION

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 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR

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 * IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

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 * Author: Carl D. Worth <cworth@cworth.org>

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*/

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/* Bug history

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 * 2005-06-01  Carl Worth  <cworth@cworth.org>

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 *   There's a long-standing bug in that self-intersecting paths give

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 *   an incorrect result when stroked. The problem is that the

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 *   trapezoids are generated incrementally along the stroke and as

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 *   such, are not disjoint. The errant intersections of these

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 *   trapezoids then leads to overfilled pixels.

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 *   The test belows first creates and fills a path. Then it creates a

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 *   second path which has a stroked boundary identical to the first

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 *   filled path. But the results of the two operations are

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 *   different. The most obvious difference is in the central region

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 *   where the entire path intersects itself. But notice that every

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 *   time the path turns there are also errors on the inside of the

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 *   turn, (since the subsequent trapezoids along the path intersect).

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*/

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#include "cairo-test.h"

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static cairo_test_status_t

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3

draw (cairo_t *cr, int width, int height)

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3

    cairo_set_source_rgb (cr, 1, 1, 1);

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3

    cairo_paint (cr);

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3

    cairo_translate (cr, 1.0, 1.0);

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3

    cairo_set_source_rgb (cr, 1, 0, 0); /* red */

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    /* First draw the desired shape with a fill */

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3

    cairo_rectangle (cr, 0.5, 0.5,  4.0, 4.0);

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3

    cairo_rectangle (cr, 3.5, 3.5,  4.0, 4.0);

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3

    cairo_rectangle (cr, 3.5, 1.5, -2.0, 2.0);

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    cairo_rectangle (cr, 6.5, 4.5, -2.0, 2.0);

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    cairo_fill (cr);

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    /* Then try the same thing with a stroke */

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3

    cairo_translate (cr, 0, 10);

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3

    cairo_move_to (cr, 1.0, 1.0);

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3

    cairo_rel_line_to (cr,  3.0,  0.0);

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3

    cairo_rel_line_to (cr,  0.0,  6.0);

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3

    cairo_rel_line_to (cr,  3.0,  0.0);

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3

    cairo_rel_line_to (cr,  0.0, -3.0);

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    cairo_rel_line_to (cr, -6.0,  0.0);

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    cairo_close_path (cr);

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    cairo_set_line_width (cr, 1.0);

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    cairo_stroke (cr);

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    return CAIRO_TEST_SUCCESS;

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CAIRO_TEST (self_intersecting,

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	    "Test strokes of self-intersecting paths"

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	    "\nSelf-intersecting strokes are wrong due to incremental trapezoidization.",

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	    "stroke, trap", /* keywords */

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	    NULL, /* requirements */

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	    10, 20,

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	    NULL, draw)