Add new miter-precision test. Checks miter joins at many scales.

This demonstrates an error in cairo where miter joins are replaced with
bevels at high scale factors due to a test added to eliminate wild miters
drawn when the line faces are nearly parallel.

Cherry picked from commit 81e029edda8c0404c6f0bd1b618e77fb55777c64

4 files changed, 82 insertions, 0 deletions

diff --git a/test/.gitignore b/test/.gitignore
index 875c1c93..20fdd906 100644
--- a/test/.gitignore
+++ b/test/.gitignore
@@ -78,6 +78,7 @@ long-lines
 mask
 mask-ctm
 mask-surface-ctm
+miter-precision
 move-to-show-surface
 multi-page
 multi-page.pdf
diff --git a/test/Makefile.am b/test/Makefile.am
index 716f558a..cd09bd1c 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -61,6 +61,7 @@ long-lines			\
 mask				\
 mask-ctm			\
 mask-surface-ctm		\
+miter-precision			\
 move-to-show-surface		\
 new-sub-path			\
 nil-surface			\
diff --git a/test/miter-precision-ref.png b/test/miter-precision-ref.png
new file mode 100644
index 00000000..c9f7f5bd
--- /dev/null
+++ b/test/miter-precision-ref.png
diff --git a/test/miter-precision.c b/test/miter-precision.c
new file mode 100644
index 00000000..09cf4937
--- /dev/null
+++ b/test/miter-precision.c
@@ -0,0 +1,80 @@
+/*
+ * Copyright © 2007 Keith Packard
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it either under the terms of the GNU Lesser General Public
+ * License version 2.1 as published by the Free Software Foundation
+ * (the "LGPL") or, at your option, under the terms of the Mozilla
+ * Public License Version 1.1 (the "MPL"). If you do not alter this
+ * notice, a recipient may use your version of this file under either
+ * the MPL or the LGPL.
+ *
+ * You should have received a copy of the LGPL along with this library
+ * in the file COPYING-LGPL-2.1; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ * You should have received a copy of the MPL along with this library
+ * in the file COPYING-MPL-1.1
+ *
+ * The contents of this file are subject to the Mozilla Public License
+ * Version 1.1 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
+ * OF ANY KIND, either express or implied. See the LGPL or the MPL for
+ * the specific language governing rights and limitations.
+ *
+ * The Original Code is the cairo graphics library.
+ *
+ * The Initial Developer of the Original Code is Keith Packard
+ *
+ * Contributor(s):
+ *      Keith Packard <keithp@keithp.com>
+ */
+#include "cairo-test.h"
+
+static cairo_test_draw_function_t draw;
+
+cairo_test_t test = {
+    "miter-precision",
+    "test how cairo deals with small miters"
+    "\ncurrent code draws inappropriate bevels at times",
+    120, 100,
+    draw
+};
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    double  xscale, yscale;
+    cairo_set_source_rgb (cr, 1, 1, 1);
+    cairo_paint (cr);
+
+    cairo_set_source_rgb (cr, 0, 0, 0);
+    cairo_set_miter_limit (cr, 100000);
+    for (xscale = 1; xscale <= 1000; xscale += 999)
+	for (yscale = 1; yscale <= 1000; yscale += 999)
+	{
+	    double  max_scale = xscale > yscale ? xscale : yscale;
+	    cairo_save (cr);
+	    if (xscale > 1)
+		cairo_translate (cr, 50, 0);
+	    if (yscale > 1)
+		cairo_translate (cr, 0, 50);
+	    cairo_scale (cr, xscale, yscale);
+	    cairo_set_line_width (cr, 10.0 / max_scale);
+	    cairo_move_to (cr, 10.0 / xscale, 10.0 / yscale);
+	    cairo_line_to (cr, 40.0 / xscale, 10.0 / yscale);
+	    cairo_line_to (cr, 10.0 / xscale, 30.0 / yscale);
+	    cairo_stroke (cr);
+	    cairo_restore (cr);
+	}
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+int
+main (void)
+{
+    return cairo_test (&test);
+}