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d3c4349730
The issue being that as the on-stack data is being referenced via a zero-copy snapshot outside of the functions scope as the surface is only finished and the source written long after the draw() returns. The correct procedure is that the user must call cairo_surface_finish() prior to any surface becoming inaccessible. In this case, this triggers the snapshot to preserve a copy of the data whilst it is still valid.
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 "Stange 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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