test: Add clip-polygons

To exercise the recent bug found in handling empty clip surfaces.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

test/Makefile.sources

@@ -58,6 +58,7 @@ test_sources = \
 	clip-nesting.c					\
 	clip-operator.c					\
 	clip-push-group.c				\
+	clip-polygons.c					\
 	clip-rectilinear.c				\
 	clip-shape.c					\
 	clip-stroke.c					\

test/clip-polygons.c

@@ -0,0 +1,112 @@
+/*
+ * Copyright © 2011 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy,
+ * modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * Author: Chris Wilson <chris@chris-wilson.co.uk>
+ */
+
+#include "cairo-test.h"
+
+#define STEP	5
+#define WIDTH	100
+#define HEIGHT	100
+
+static void diamond (cairo_t *cr)
+{
+    cairo_move_to (cr, WIDTH/2, 0);
+    cairo_line_to (cr, WIDTH, HEIGHT/2);
+    cairo_line_to (cr, WIDTH/2, HEIGHT);
+    cairo_line_to (cr, 0, HEIGHT/2);
+    cairo_close_path (cr);
+}
+
+static void background (cairo_t *cr)
+{
+    cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
+    cairo_set_source_rgb (cr, 1,1,1);
+    cairo_paint (cr);
+    cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
+    cairo_set_source_rgb (cr, 0,0,0);
+}
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    background (cr);
+
+    /* completely overlapping diamonds */
+    cairo_save (cr);
+    diamond (cr);
+    cairo_clip (cr);
+    diamond (cr);
+    cairo_clip (cr);
+    cairo_paint (cr);
+    cairo_restore (cr);
+
+    cairo_translate (cr, WIDTH, 0);
+
+    /* partial overlap */
+    cairo_save (cr);
+    cairo_translate (cr, -WIDTH/4, 0);
+    diamond (cr);
+    cairo_clip (cr);
+    cairo_translate (cr, WIDTH/2, 0);
+    diamond (cr);
+    cairo_clip (cr);
+    cairo_paint (cr);
+    cairo_restore (cr);
+
+    cairo_translate (cr, WIDTH, 0);
+
+    /* no overlap, but the bounding boxes must */
+    cairo_save (cr);
+    cairo_translate (cr, -WIDTH/2 + 2, -2);
+    diamond (cr);
+    cairo_clip (cr);
+    cairo_translate (cr, WIDTH - 4, 4);
+    diamond (cr);
+    cairo_clip (cr);
+    cairo_paint (cr);
+    cairo_restore (cr);
+
+    cairo_translate (cr, WIDTH, 0);
+
+    /* completely disjoint */
+    cairo_save (cr);
+    cairo_translate (cr, -WIDTH/2 - 1, 0);
+    diamond (cr);
+    cairo_clip (cr);
+    cairo_translate (cr, WIDTH + 2, 0);
+    diamond (cr);
+    cairo_clip (cr);
+    cairo_paint (cr);
+    cairo_restore (cr);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+CAIRO_TEST (clip_polygons,
+	    "Test drawing through through an intersection of polygons",
+	    "clip", /* keywords */
+	    "target=raster", /* requirements */
+	    4*WIDTH, HEIGHT,
+	    NULL, draw)