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/*
* Copyright © 2009 M Joonas Pihlaja
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy,
* modify, merge, publish, distribute, sublicense, and/or sell copies
* of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
* Author: M Joonas Pihlaja <jpihlaja@cc.helsinki.fi>
*/
#include "cairo-test.h"
/* When faced with very small dash lengths the stroker is liable to
* get stuck in an infinite loop when advancing the dash offset. This
* test attempts to hit each of the locations in the stroker code
* where the dash offset is advanced in a loop.
*
* Reported to the cairo mailing list by Hans Breuer.
* http://lists.cairographics.org/archives/cairo/2009-June/017506.html
*/
#define EPS 1e-30
/* This should be comfortably smaller than the unit epsilon of the
* floating point type used to advance the dashing, yet not small
* enough that it underflows to zero. 1e-30 works to foil up to 80
* bit extended precision arithmetic. We want to avoid zero dash
* lengths because those trigger special processing in the stroker. */
static void
do_dash (cairo_t *cr, double dx, double dy, double offset)
{
/* Set the dash pattern to be predominantly ON so that we can
* create a reference image by just ignoring the dashing. */
static double dash[] = { EPS, EPS/512 };
cairo_set_dash (cr, dash, 2, offset);
cairo_move_to (cr, 10, 10);
cairo_rel_line_to (cr, dx, dy);
cairo_stroke (cr);
cairo_translate (cr, dx, dy);
}
static cairo_test_status_t
draw (cairo_t *cr, int width, int height)
{
(void)width; (void)height;
cairo_set_source_rgb (cr, 1,1,1);
cairo_paint (cr);
cairo_set_source_rgb (cr, 0,0,0);
cairo_set_line_width (cr, 10);
/* The following calls will wedge in various places that try
* to advance the dashing in a loop inside the stroker. */
do_dash (cr, 30, 30, 1); /* _cairo_stroker_dash_start */
do_dash (cr, 30, 30, 0); /* _cairo_stroker_line_to_dashed */
do_dash (cr, 30, 0, 0); /* _cairo_rectilinear_stroker_line_to_dashed */
return CAIRO_TEST_SUCCESS;
}
CAIRO_TEST (dash_infinite_loop,
"Test dashing with extremely small dash lengths.",
"dash",
NULL,
100, 100,
NULL, draw);
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