/* * Copyright 2010 Soeren Sandmann Pedersen * * 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: Soeren Sandmann <sandmann@daimi.au.dk> */ /* Exercises a case of seam appearing between two polygons in the image * backend but not in xlib [using pixman]. * * The test case draws two abutting quads both individually on the * leftm combining them with operator ADD, and in one go on the right. * Both methods should show no signs of seaming at the common edge * between the two quads, but the individually drawn ones have a * slight seam. * * The cause of the seam is that there are slight differences in the * output of the analytical coverage rasterization and the * supersampling rasterization methods, both employed by * cairo-tor-scan-converter. When drawn individually, the scan * converter gets a partial view of the geometry at a time, so it ends * up making different decisions about which scanlines it rasterizes * with which method, compared to when the geometry is draw all at * once. Though both methods produce seamless results individually * (where applicable), they don't produce bit-exact identical results, * and hence we get seaming where they meet. */ #include "cairo-test.h" static void draw_quad (cairo_t *cr, double x1, double y1, double x2, double y2, double x3, double y3, double x4, double y4) { cairo_move_to (cr, x1, y1); cairo_line_to (cr, x2, y2); cairo_line_to (cr, x3, y3); cairo_line_to (cr, x4, y4); cairo_close_path (cr); } static cairo_test_status_t draw (cairo_t *cr, int width, int height) { cairo_set_source_rgb (cr, 0, 0, 0); cairo_paint (cr); cairo_scale (cr, 20, 20); cairo_translate (cr, 5, 1); /* On the left side, we have two quads drawn one at a time and * combined with OPERATOR_ADD. This should be seamless, but * isn't. */ cairo_push_group (cr); cairo_set_operator (cr, CAIRO_OPERATOR_ADD); cairo_set_source_rgb (cr, 0, 0.6, 0); draw_quad (cr, 1.50, 1.50, 2.64, 1.63, 1.75, 2.75, 0.55, 2.63); cairo_fill (cr); draw_quad (cr, 0.55, 2.63, 1.75, 2.75, 0.98, 4.11, -0.35, 4.05); cairo_fill (cr); cairo_pop_group_to_source (cr); cairo_set_operator (cr, CAIRO_OPERATOR_OVER); cairo_paint (cr); /* On the right side, we have the same two quads drawn both at the * same time. This is seamless. */ cairo_translate (cr, 10, 0); cairo_set_source_rgb (cr, 0, 0.6, 0); draw_quad (cr, 1.50, 1.50, 2.64, 1.63, 1.75, 2.75, 0.55, 2.63); draw_quad (cr, 0.55, 2.63, 1.75, 2.75, 0.98, 4.11, -0.35, 4.05); cairo_fill (cr); return CAIRO_TEST_SUCCESS; } CAIRO_TEST (bug_seams, "Check the fidelity of the rasterisation.", "raster", /* keywords */ "target=raster", /* requirements */ 500, 300, NULL, draw)