[test] Add a test case for create_similar(CONTENT_ALPHA)

Application of a pure-alpha similar source is inconsistently handled
across the backends. The PDF/PS backends allow the rgb channels to bleed
through and the SVG backend mixes in pure white.

test/.gitignore

@@ -10,6 +10,7 @@ a1-image-sample
 a1-mask
 a1-traps-sample
 a8-mask
+alpha-similar
 any2ppm
 .any2ppm
 .any2ppm.pid

test/Makefile.am

@@ -8,6 +8,7 @@ a1-image-sample$(EXEEXT)				\
 a1-mask$(EXEEXT)					\
 a1-traps-sample$(EXEEXT)				\
 a8-mask$(EXEEXT)					\
+alpha-similar$(EXEEXT)					\
 big-line$(EXEEXT)					\
 big-trap$(EXEEXT)					\
 bilevel-image$(EXEEXT)					\
@@ -291,6 +292,8 @@ REFERENCE_IMAGES = \
 	a1-mask-ref.png	\
 	a1-traps-sample-ref.png		\
 	a8-mask-ref.png	\
+	alpha-similar-ref.png	\
+	alpha-similar-rgb24-ref.png	\
 	big-line-ref.png		\
 	big-line-rgb24-ref.png		\
 	big-line-ps-ref.png		\

test/alpha-similar.c

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2008 Chris Wilson
+ *
+ * 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
+ * Chris Wilson not be used in advertising or publicity pertaining to
+ * distribution of the software without specific, written prior
+ * permission. Chris Wilson makes no representations about the
+ * suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * CHRIS WILSON DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
+ * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS, IN NO EVENT SHALL CHRIS WILSON 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: Chris Wilson <chris@chris-wilson.co.uk>
+ */
+
+#include "cairo-test.h"
+
+static cairo_test_draw_function_t draw;
+
+static const cairo_test_t test = {
+    "alpha-similar",
+    "Tests creation of similar alpha surfaces",
+    10, 10,
+    draw
+};
+
+static cairo_surface_t *
+create_source (cairo_surface_t *target, int width, int height)
+{
+    cairo_surface_t *similar;
+    cairo_t *cr;
+
+    similar = cairo_surface_create_similar (target,
+					    CAIRO_CONTENT_ALPHA,
+					    width, height);
+    cr = cairo_create (similar);
+    cairo_surface_destroy (similar);
+
+    cairo_set_source_rgba (cr, 1, 0, 0, .5);
+    cairo_paint (cr);
+
+    similar = cairo_surface_reference (cairo_get_target (cr));
+    cairo_destroy (cr);
+
+    return similar;
+}
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    cairo_surface_t *source;
+
+    source = create_source (cairo_get_target (cr), width, height);
+    cairo_set_source_surface (cr, source, 0, 0);
+    cairo_surface_destroy (source);
+
+    cairo_paint (cr);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+int
+main (void)
+{
+    return cairo_test (&test);
+}