Grcov report - zero-alpha.c

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/*

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 * Copyright © 2006 Red Hat, Inc.

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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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 * 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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 * 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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 * 2006-06-13 Paul Giblock reports a "Strange alpha channel problem" on

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 * the cairo mailing list.

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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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 * 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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3

draw (cairo_t *cr, int width, int height)

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    int i;

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    cairo_surface_t *surface;

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3

    uint32_t zero = 0;

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    /* First paint background red. */

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3

    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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3

    cairo_set_source_rgba (cr, 0.0, 0.0, 0.0, 0.0); /* transparent */

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3

    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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3

    cairo_new_path (cr);

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    /* 2. paint with a zero-alpha image surface source. */

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3

    surface = cairo_image_surface_create_for_data ((unsigned char *) &zero,

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						   CAIRO_FORMAT_ARGB32, 1, 1, 4);

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3

    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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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)