cairo/test/in-fill-empty-trapezoid.c

   1 /*
   2  * Copyright © 2006 M Joonas Pihlaja
   3  *
   4  * Permission is hereby granted, free of charge, to any person
   5  * obtaining a copy of this software and associated documentation
   6  * files (the "Software"), to deal in the Software without
   7  * restriction, including without limitation the rights to use, copy,
   8  * modify, merge, publish, distribute, sublicense, and/or sell copies
   9  * of the Software, and to permit persons to whom the Software is
  10  * furnished to do so, subject to the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be
  13  * included in all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22  * SOFTWARE.
  23  *
  24  * Author: M Joonas Pihlaja <jpihlaja@cc.helsinki.fi>
  25  */
  26
  27 /* Bug history
  28  *
  29  * 2006-12-05  M Joonas Pihlaja <jpihlaja@cc.helsinki.fi>
  30  *
  31  *  The cairo_in_fill () function can sometimes produce false
  32  *  positives when the tessellator produces empty trapezoids
  33  *  and the query point lands exactly on a trapezoid edge.
  34  */
  35
  36 #include "cairo-test.h"
  37
  38 int
  39 main (void)
  40 {
  41     cairo_test_context_t ctx;
  42     int x,y;
  43     int width = 10;
  44     int height = 10;
  45     cairo_surface_t *surf;
  46     cairo_t *cr;
  47     int false_positive_count = 0;
  48     cairo_status_t status;
  49     char const * description =
  50         "Test that the tessellator isn't producing obviously empty trapezoids";
  51     cairo_test_status_t ret;
  52
  53     cairo_test_init (&ctx, "in-fill-empty-trapezoid");
  54     cairo_test_log (&ctx, "%s\n", description);
  55     printf ("%s\n", description);
  56
  57     surf = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, width, height);
  58     cr = cairo_create (surf);
  59     cairo_surface_destroy (surf);
  60
  61     /* Empty horizontal trapezoid. */
  62     cairo_move_to (cr, 0, height/3);
  63     cairo_line_to (cr, width, height/3);
  64     cairo_close_path (cr);
  65
  66     /* Empty non-horizontal trapezoid #1. */
  67     cairo_move_to (cr, 0, 0);
  68     cairo_line_to (cr, width, height/2);
  69     cairo_close_path (cr);
  70
  71     /* Empty non-horizontal trapezoid #2 intersecting #1. */
  72     cairo_move_to (cr, 0, height/2);
  73     cairo_line_to (cr, width, 0);
  74     cairo_close_path (cr);
  75
  76     status = cairo_status (cr);
  77
  78     /* Point sample the tessellated path. */
  79     for (y = 0; y < height; y++) {
  80         for (x = 0; x < width; x++) {
  81             if (cairo_in_fill (cr, x, y)) {
  82                 false_positive_count++;
  83             }
  84         }
  85     }
  86     cairo_destroy (cr);
  87
  88     /* Check that everything went well. */
  89     ret = CAIRO_TEST_SUCCESS;
  90     if (CAIRO_STATUS_SUCCESS != status) {
  91         cairo_test_log (&ctx, "Failed to create a test surface and path: %s\n",
  92                         cairo_status_to_string (status));
  93         ret = CAIRO_TEST_FAILURE;
  94     }
  95
  96     if (0 != false_positive_count) {
  97         cairo_test_log (&ctx, "Point sampling found %d false positives "
  98                         "from cairo_in_fill()\n",
  99                         false_positive_count);
 100         ret = CAIRO_TEST_FAILURE;
 101     }
 102
 103     cairo_test_fini (&ctx);
 104
 105     return ret;
 106 }