test: Add clip-contexts

This should exercise a bug found by Jeff Muizelaar that
cairo-surface-clipper was mistakenly thinking that clip operations on a
second context was a no-op as the topmost clip path matched that of the
previous context.

test/Makefile.am

@@ -168,6 +168,7 @@ REFERENCE_IMAGES = \
 	clear.svg12.rgb24.xfail.png \
 	clear-source.ref.png \
 	clip-all.ref.png \
+	clip-contexts.ref.png \
 	clip-device-offset.argb32.ref.png \
 	clip-device-offset.rgb24.ref.png \
 	clip-disjoint.ref.png \

test/Makefile.sources

@@ -17,6 +17,7 @@ test_sources = \
 	clear.c						\
 	clear-source.c					\
 	clip-all.c					\
+	clip-contexts.c					\
 	clip-disjoint.c					\
 	clip-device-offset.c				\
 	clip-empty.c					\

test/clip-contexts.c

@@ -0,0 +1,73 @@
+/*
+ * Copyright © 2010 Intel Corporation
+ *
+ * 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
+ * Intel Corporation not be used in advertising or publicity pertaining to
+ * distribution of the software without specific, written prior
+ * permission. Intel Corporation makes no representations about the
+ * suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * INTEL CORPORATION DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
+ * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS, IN NO EVENT SHALL INTEL CORPORATION 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"
+
+/*
+ * Jeff Muizelaar found a bug on Quartz with cairo-surface-clipper, which was
+ * the topmost clip path from two different contexts and finding them equally
+ * incorrectly concluding that the operation was a no-op.
+ */
+
+#define SIZE 10
+#define CLIP_SIZE 2
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    cairo_t *cr2;
+
+    /* opaque background */
+    cairo_set_source_rgb (cr, 0, 0, 0);
+    cairo_paint (cr);
+
+    /* first create an empty, non-overlappiny clip */
+    cr2 = cairo_create (cairo_get_target (cr));
+    cairo_rectangle (cr2, 0, 0, SIZE/2-2, SIZE/2-2);
+    cairo_clip (cr2);
+
+    cairo_rectangle (cr2, SIZE/2+2, SIZE/2+2, SIZE/2-2, SIZE/2-2);
+    cairo_clip (cr2);
+
+    /* and apply the clip onto the surface, empty nothing should be painted */
+    cairo_set_source_rgba (cr2, 1, 0, 0, .5);
+    cairo_paint (cr2);
+
+    /* switch back to the original, and set only the last clip */
+    cairo_rectangle (cr, SIZE/2+2, SIZE/2+2, SIZE/2-2, SIZE/2-2);
+    cairo_clip (cr);
+
+    cairo_set_source_rgba (cr, 0, 0, 1, .5);
+    cairo_paint (cr);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+CAIRO_TEST (clip_contexts,
+	    "Test clipping with 2 separate contexts",
+	    "clip", /* keywords */
+	    NULL, /* requirements */
+	    SIZE, SIZE,
+	    NULL, draw)