[test] Add degenerate-arc

This test case is to exercise the divide-by-zero error reported by
Luiz Americo Pereira Camara <luizmed@oi.com.br>,
http://lists.cairographics.org/archives/cairo/2008-May/014054.html.

test/.gitignore

@@ -43,6 +43,7 @@ dash-offset-negative
 dash-scale
 dash-state
 dash-zero-length
+degenerate-arc
 degenerate-path
 degenerate-pen
 device-offset

test/Makefile.am

@@ -36,6 +36,7 @@ dash-offset-negative$(EXEEXT)				\
 dash-scale$(EXEEXT)					\
 dash-state$(EXEEXT)					\
 dash-zero-length$(EXEEXT)				\
+degenerate-arc$(EXEEXT)					\
 degenerate-path$(EXEEXT)				\
 degenerate-pen$(EXEEXT)					\
 device-offset$(EXEEXT)					\
@@ -349,6 +350,8 @@ REFERENCE_IMAGES = \
 	dash-zero-length-ps-rgb24-ref.png	\
 	dash-zero-length-ref.png	\
 	dash-zero-length-rgb24-ref.png	\
+	degenerate-arc-ref.png		\
+	degenerate-arc-ps-ref.png	\
 	degenerate-pen-ref.png		\
 	degenerate-pen-ps-ref.png	\
 	degenerate-pen-quartz-ref.png	\

test/degenerate-arc.c

@@ -0,0 +1,82 @@
+/*
+ * 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>
+ */
+
+/* This test case exercises a "Potential division by zero in cairo_arc"
+ * reported by Luiz Americo Pereira Camara <luizmed@oi.com.br>,
+ * http://lists.cairographics.org/archives/cairo/2008-May/014054.html.
+ */
+
+#include "cairo-test.h"
+
+static cairo_test_draw_function_t draw;
+
+cairo_test_t test = {
+    "degenerate-arc",
+    "Tests the behaviour of degenerate arcs",
+    40, 40,
+    draw
+};
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    int n;
+
+    cairo_set_source_rgb (cr, 1, 1, 1);
+    cairo_paint (cr);
+
+    cairo_set_line_cap (cr, CAIRO_LINE_CAP_ROUND);
+
+    cairo_set_line_width (cr, 5);
+    cairo_set_source_rgb (cr, 0, 1, 0);
+    for (n = 0; n < 8; n++) {
+	double theta = n * 2 * M_PI / 8;
+	cairo_new_sub_path (cr);
+	cairo_arc (cr, 20, 20, 15, theta, theta);
+	cairo_close_path (cr);
+    }
+    cairo_stroke (cr);
+
+    cairo_set_line_width (cr, 2);
+    cairo_set_source_rgb (cr, 0, 0, 1);
+    for (n = 0; n < 8; n++) {
+	double theta = n * 2 * M_PI / 8;
+	cairo_move_to (cr, 20, 20);
+	cairo_arc (cr, 20, 20, 15, theta, theta);
+    }
+    cairo_stroke (cr);
+
+    cairo_set_source_rgb (cr, 1, 0, 0);
+    cairo_arc (cr, 20, 20, 2, 0, 2*M_PI);
+    cairo_fill (cr);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+int
+main (void)
+{
+    return cairo_test (&test);
+}