cairo/test/degenerate-pen.c

   1 /*
   2  * Copyright © 2007 Red Hat, Inc.
   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: Carl D. Worth <cworth@cworth.org>
  25  */
  26
  27 #include "cairo-test.h"
  28
  29 static cairo_test_draw_function_t draw;
  30
  31 #define SIZE   20
  32 #define PAD    5
  33 #define WIDTH  (PAD + 3 * (PAD + SIZE) + PAD)
  34 #define HEIGHT (PAD + SIZE + PAD)
  35
  36 /* We're demonstrating here a bug originally reported by Benjamin Otte
  37  * on the cairo mailing list here, (after he ran into this problem
  38  * with various flash animations):
  39  *
  40  *      [cairo] Assertion `i < pen->num_vertices' failed in 1.4.10
  41  *      http://lists.cairographics.org/archives/cairo/2007-August/011282.html
  42  *
  43  * The problem shows up with an extreme transformation matrix that
  44  * collapses the pen to a single line, (which means that
  45  * _cairo_slope_compare cannot handle adjacent vertices in the pen
  46  * since they have parallel slope).
  47  *
  48  * This test case tests degenerate pens in several directions and uses
  49  * round caps to force the stroking code to attempt to walk around the
  50  * pen doing slope comparisons.
  51  */
  52
  53 static const cairo_test_t test = {
  54     "degenerate-pen",
  55     "Test round joins with a pen that's transformed to a line",
  56     WIDTH, HEIGHT,
  57     draw
  58 };
  59
  60 static cairo_test_status_t
  61 draw (cairo_t *cr, int width, int height)
  62 {
  63     cairo_set_source_rgb (cr, 1, 1, 1);
  64     cairo_paint (cr);
  65
  66     cairo_set_source_rgb (cr, 0, 0, 0);
  67     cairo_set_line_join (cr, CAIRO_LINE_JOIN_ROUND);
  68
  69     cairo_translate (cr, PAD, PAD);
  70
  71     /* First compress the pen to a vertical line. */
  72     cairo_rectangle (cr, 0, 0, SIZE, SIZE);
  73     cairo_curve_to (cr, SIZE / 2, 0, SIZE, SIZE / 2, SIZE, SIZE);
  74     cairo_save (cr);
  75     {
  76         cairo_scale (cr, 0.000001, 1.0);
  77         cairo_stroke (cr);
  78     }
  79     cairo_restore (cr);
  80
  81     cairo_translate (cr, PAD + SIZE, 0);
  82
  83     /* Then compress the pen to a horizontal line. */
  84     cairo_rectangle (cr, 0, 0, SIZE, SIZE);
  85     cairo_curve_to (cr, SIZE / 2, 0, SIZE, SIZE / 2, SIZE, SIZE);
  86     cairo_save (cr);
  87     {
  88         cairo_scale (cr, 1.0, 0.000001);
  89         cairo_stroke (cr);
  90     }
  91     cairo_restore (cr);
  92
  93     cairo_translate (cr, PAD + SIZE, 0);
  94
  95     /* Finally a line at an angle. */
  96     cairo_rectangle (cr, 0, 0, SIZE, SIZE);
  97     cairo_curve_to (cr, SIZE / 2, 0, SIZE, SIZE / 2, SIZE, SIZE);
  98     cairo_save (cr);
  99     {
 100         cairo_rotate (cr, M_PI / 4.0);
 101         cairo_scale (cr, 0.000001, 1.0);
 102         cairo_stroke (cr);
 103     }
 104     cairo_restore (cr);
 105
 106     return CAIRO_TEST_SUCCESS;
 107 }
 108
 109 int
 110 main (void)
 111 {
 112     return cairo_test (&test);
 113 }