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Diffstat (limited to 'libs/cairo-1.16.0/test/self-intersecting.c')
| -rw-r--r-- | libs/cairo-1.16.0/test/self-intersecting.c | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/libs/cairo-1.16.0/test/self-intersecting.c b/libs/cairo-1.16.0/test/self-intersecting.c new file mode 100644 index 0000000..8053235 --- /dev/null +++ b/libs/cairo-1.16.0/test/self-intersecting.c @@ -0,0 +1,87 @@ +/* + * 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" + +static cairo_test_status_t +draw (cairo_t *cr, int width, int height) +{ + cairo_set_source_rgb (cr, 1, 1, 1); + cairo_paint (cr); + + 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; +} + +CAIRO_TEST (self_intersecting, + "Test strokes of self-intersecting paths" + "\nSelf-intersecting strokes are wrong due to incremental trapezoidization.", + "stroke, trap", /* keywords */ + NULL, /* requirements */ + 10, 20, + NULL, draw) |