[test] Check idempotency of append_path() -> copy_path()

The API should preserve the precision across the public interface so that
the user is able to retrieve the co-ordinates that he used to construct
the path. However since we transform the path to a 24.8 fixed-point
internal represent we currently incur a precision-loss - the affects of
which can be seen in the miter-precision test case for example. It is
planned to move to keeping the path as doubles until the backend
explicitly requests the fixed-point coodinates (and some backends, e.g.
pdf, might only ever use the doubles). Then, barring rounding errors
during path transformations, we should be able to return the exact path
the user set (under an identity CTM, of course ;-).

1 files changed, 108 insertions, 0 deletions

diff --git a/test/path-precision.c b/test/path-precision.c
new file mode 100644
index 000000000..447b7a246
--- /dev/null
+++ b/test/path-precision.c
@@ -0,0 +1,108 @@
+/*
+ * 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>
+ *
+ * Based on an example by Dirk "krit" Schulze found during WebKit integration.
+ */
+
+#include "cairo-test.h"
+
+/* Test the idempotency of path construction and copying */
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    cairo_path_data_t path_data[] = {
+	{ .header = { CAIRO_PATH_MOVE_TO, 2 }, },
+	{ .point = { 95.000000, 40.000000 }, },
+
+	{ .header = { CAIRO_PATH_LINE_TO, 2 }, },
+	{ .point = { 94.960533, 41.255810 }, },
+
+	{ .header = { CAIRO_PATH_LINE_TO, 2 }, },
+	{ .point = { 94.842293, 42.50666 }, },
+
+	{ .header = { CAIRO_PATH_LINE_TO, 2 }, },
+	{ .point = { 94.645744, 43.747627 }, },
+
+	{ .header = { CAIRO_PATH_LINE_TO, 2 }, },
+	{ .point = { 94.371666, 44.973797 }, },
+    };
+    const cairo_test_context_t *ctx = cairo_test_get_context (cr);
+    cairo_path_t path, *path_copy;
+    int i, j, n;
+    cairo_test_status_t result = CAIRO_TEST_SUCCESS;
+
+    path.status = CAIRO_STATUS_SUCCESS;
+    path.num_data = sizeof (path_data) / sizeof (path_data[0]);
+    path.data = path_data;
+
+    cairo_new_path (cr);
+    cairo_append_path (cr, &path);
+    path_copy = cairo_copy_path (cr);
+
+    if (path_copy->status)
+	return cairo_test_status_from_status (ctx, path_copy->status);
+
+    for (i = j = n = 0;
+	 i < path.num_data && j < path_copy->num_data;
+	 i += path.data[i].header.length,
+	 j += path_copy->data[j].header.length,
+	 n++)
+    {
+	const cairo_path_data_t *src, *dst;
+
+	src = &path.data[i];
+	dst = &path_copy->data[j];
+
+	if (src->header.type != dst->header.type) {
+	    cairo_test_log (ctx,
+			    "Paths differ in header type after %d operations.\n"
+			    "Expected path operation %d, found %d.\n",
+			    n, src->header.type, dst->header.type);
+	    result = CAIRO_TEST_FAILURE;
+	    break;
+	}
+
+	if (memcmp (&src[1].point, &dst[1].point, sizeof (src->point))) {
+	    cairo_test_log (ctx,
+			    "Paths differ in coordinates after %d operations.\n"
+			    "Expected point (%f, %f), found (%f, %f).\n",
+			    n,
+			    src[1].point.x, src[1].point.y,
+			    dst[1].point.x, dst[1].point.y);
+	    result = CAIRO_TEST_FAILURE;
+	    break;
+	}
+    }
+
+    cairo_path_destroy (path_copy);
+    return result;
+}
+
+CAIRO_TEST (path_precision,
+	    "Check that the path append/copy is idempotent.",
+	    "XFAIL api", /* keywords */
+	    NULL, /* requirements */
+	    0, 0,
+	    NULL, draw)