/* * 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, 0); /* _cairo_stroker_line_to_dashed */ do_dash (cr, 30, 0, 0); /* _cairo_rectilinear_stroker_line_to_dashed */ do_dash (cr, 30, 30, 1); /* _cairo_stroker_dash_start */ return CAIRO_TEST_SUCCESS; } CAIRO_TEST (dash_infinite_loop, "Test dashing with extremely small dash lengths.", "dash", NULL, 100, 100, NULL, draw);