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/*
* Copyright © 2006 Red Hat, Inc.
*
* Permission to use, copy, modify, distribute, and sell this software
* and its documentation for any purpose is hereby granted without
* fee, provided that the above copyright notice appear in all copies
* and that both that copyright notice and this permission notice
* appear in supporting documentation, and that the name of
* Red Hat, Inc. not be used in advertising or publicity pertaining to
* distribution of the software without specific, written prior
* permission. Red Hat, Inc. makes no representations about the
* suitability of this software for any purpose. It is provided "as
* is" without express or implied warranty.
*
* RED HAT, INC. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
* SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS, IN NO EVENT SHALL RED HAT, INC. BE LIABLE FOR ANY SPECIAL,
* INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
* RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
* IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* Author: Carl D. Worth <cworth@cworth.org>
*/
#include "cairo-test.h"
#define SIZE 3
#define REPS 10
/* History:
*
* 2006-06-13 Paul Giblock reports a "Strange alpha channel problem" on
* the cairo mailing list.
*
* 2006-06-13 Carl Worth writes this test in an attempt to reproduce
* the problem. The test first fills in a 3x3 rectangle with red, then
* starts pounding on that center pixel with various forms of
* zero-alpha rendering to see if its value can ever be made to
* change.
*
* 2006-06-13 Paul Giblock reports that this only happens with the
* xlib backend, and then only on some systems.
*/
static cairo_test_status_t
draw (cairo_t *cr, int width, int height)
{
int i;
cairo_surface_t *surface;
uint32_t zero = 0;
/* First paint background red. */
cairo_set_source_rgb (cr, 1.0, 0.0, 0.0); /* red */
cairo_paint (cr);
/* Then we paint zero-alpha in several ways (always REPS times): */
/* 1. fill a rectangle with a zero-alpha solid source. */
cairo_set_source_rgba (cr, 0.0, 0.0, 0.0, 0.0); /* transparent */
cairo_rectangle (cr, 1.0, 1.0, 1.0, 1.0);
for (i=0; i < REPS; i++)
cairo_fill_preserve (cr);
cairo_new_path (cr);
/* 2. paint with a zero-alpha image surface source. */
surface = cairo_image_surface_create_for_data ((unsigned char *) &zero,
CAIRO_FORMAT_ARGB32, 1, 1, 4);
cairo_set_source_surface (cr, surface, 1, 1);
for (i=0; i < REPS; i++)
cairo_paint (cr);
/* 3. clip to rectangle then paint with zero-alpha solid source. */
cairo_rectangle (cr, 1.0, 1.0, 1.0, 1.0);
cairo_clip (cr);
cairo_set_source_rgba (cr, 0.0, 0.0, 0.0, 0.0); /* transparent */
for (i=0; i < REPS; i++)
cairo_paint (cr);
/* 4. With the clip still there, paint our image surface. */
cairo_set_source_surface (cr, surface, 1, 1);
for (i=0; i < REPS; i++)
cairo_paint (cr);
cairo_surface_finish (surface); /* zero will go out of scope */
cairo_surface_destroy (surface);
return CAIRO_TEST_SUCCESS;
}
CAIRO_TEST (zero_alpha,
"Testing that drawing with zero alpha has no effect",
"alpha", /* keywords */
NULL, /* requirements */
SIZE, SIZE,
NULL, draw)
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