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