source-clip.c

按照官方的说法：Cairo is a vector graphics library with cross-device output support. 翻译过来

/*
 * Copyright © 2005 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: Owen Taylor <[e-mail]>
 */

#include <math.h>
#include "cairo-test.h"
#include <stdio.h>

#define SIZE 50

cairo_test_t test = {
    "source-clip",
    "Test using a surface with an active clip as a source",
    SIZE, SIZE
};

static cairo_test_status_t
draw (cairo_t *cr, int width, int height)
{
    cairo_pattern_t *pattern;
    cairo_surface_t *source_surface;
    cairo_t *cr2;

    source_surface = cairo_surface_create_similar (cairo_get_target (cr),
						   CAIRO_CONTENT_COLOR_ALPHA,
						   SIZE, SIZE);

    cr2 = cairo_create (source_surface);

    /* Fill the source surface with solid black */
    cairo_set_source_rgb (cr2, 0, 0, 0);
    cairo_paint (cr2);

    /* Now leave a clip in place */
    cairo_rectangle (cr2,
		     SIZE / 4, SIZE / 4,
		     SIZE / 2, SIZE / 2);
    cairo_clip (cr2);

    /* Fill the destination surface with solid white */
    cairo_set_source_rgb (cr, 1, 1, 1);
    cairo_paint (cr);

    /* Now draw the source surface onto the destination surface */
    pattern = cairo_pattern_create_for_surface (source_surface);
    cairo_set_source (cr, pattern);
    cairo_paint (cr);

    /* As the clip shouldn't matter, the result should be solid black */

    cairo_destroy (cr2);
    cairo_pattern_destroy (pattern);
    cairo_surface_destroy (source_surface);

    return CAIRO_TEST_SUCCESS;

}

int
main (void)
{
    return cairo_test (&test, draw);
}