/* * 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 "Stange 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)