cairo/test/leaky-polygon.c

   1 /*
   2  * Copyright © 2005 Red Hat, Inc.
   3  *
   4  * Permission to use, copy, modify, distribute, and sell this software
   5  * and its documentation for any purpose is hereby granted without
   6  * fee, provided that the above copyright notice appear in all copies
   7  * and that both that copyright notice and this permission notice
   8  * appear in supporting documentation, and that the name of
   9  * Red Hat, Inc. not be used in advertising or publicity pertaining to
  10  * distribution of the software without specific, written prior
  11  * permission. Red Hat, Inc. makes no representations about the
  12  * suitability of this software for any purpose.  It is provided "as
  13  * is" without express or implied warranty.
  14  *
  15  * RED HAT, INC. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
  16  * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
  17  * FITNESS, IN NO EVENT SHALL RED HAT, INC. BE LIABLE FOR ANY SPECIAL,
  18  * INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
  19  * RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
  20  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
  21  * IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  22  *
  23  * Author: Carl D. Worth <cworth@cworth.org>
  24  */
  25
  26 /* Bug history
  27  *
  28  * 2005-01-07 Carl Worth <cworth@cworth.org>
  29  *
  30  *   Bug reported:
  31  *
  32  *     From: Chris <fltk@functionalfuture.com>
  33  *     Subject: [cairo] Render to image buffer artifacts
  34  *     To: cairo@cairographics.org
  35  *     Date: Fri, 07 Jan 2005 02:22:28 -0500
  36  *
  37  *     I've attached the code and image that shows this off.  Scaling at
  38  *     different levels seems to change the corruption.
  39  *
  40  *     For some reason there are artifacts in the alpha channel.  I don't know
  41  *     if that's the only place, but the alpha channel looks bad.
  42  *
  43  *     If you run the code and parse the attached image, directing stdout to a
  44  *     file, you can see in the lower left corner there are alpha values where
  45  *     it should be transparent.
  46  *     [...]
  47  *
  48  * 2005-01-11 Carl Worth <cworth@cworth.org>
  49  *
  50  *   I trimmed the original test case down to the code that appears here.
  51  *
  52  */
  53
  54 #include "cairo-test.h"
  55
  56 #define WIDTH 21
  57 #define HEIGHT 21
  58
  59 static cairo_test_draw_function_t draw;
  60
  61 static const cairo_test_t test = {
  62     "leaky-polygon",
  63     "Exercises a corner case in the trapezoid rasterization in which pixels outside the trapezoids received a non-zero alpha",
  64     WIDTH, HEIGHT,
  65     draw
  66 };
  67
  68 static cairo_test_status_t
  69 draw (cairo_t *cr, int width, int height)
  70 {
  71     /* We draw in the default black, so paint white first. */
  72     cairo_save (cr);
  73     cairo_set_source_rgb (cr, 1.0, 1.0, 1.0); /* white */
  74     cairo_paint (cr);
  75     cairo_restore (cr);
  76
  77     cairo_scale (cr, 1.0/(1<<16), 1.0/(1<<16));
  78
  79     cairo_move_to (cr, 131072,39321);
  80     cairo_line_to (cr, 1103072,1288088);
  81     cairo_line_to (cr, 1179648,1294990);
  82     cairo_close_path (cr);
  83
  84     cairo_fill (cr);
  85
  86     return CAIRO_TEST_SUCCESS;
  87 }
  88
  89 int
  90 main (void)
  91 {
  92     return cairo_test (&test);
  93 }