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Diffstat (limited to 'libs/cairo-1.16.0/test/bug-seams.c')
-rw-r--r-- | libs/cairo-1.16.0/test/bug-seams.c | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/libs/cairo-1.16.0/test/bug-seams.c b/libs/cairo-1.16.0/test/bug-seams.c new file mode 100644 index 0000000..01e84ff --- /dev/null +++ b/libs/cairo-1.16.0/test/bug-seams.c @@ -0,0 +1,120 @@ +/* + * 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) |