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diff --git a/libs/cairo-1.16.0/src/cairo-slope.c b/libs/cairo-1.16.0/src/cairo-slope.c
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+++ b/libs/cairo-1.16.0/src/cairo-slope.c
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+/* cairo - a vector graphics library with display and print output
+ *
+ * Copyright © 2002 University of Southern California
+ *
+ * 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., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, 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 University of Southern
+ * California.
+ *
+ * Contributor(s):
+ *	Carl D. Worth <cworth@cworth.org>
+ */
+
+#include "cairoint.h"
+
+#include "cairo-slope-private.h"
+
+/* Compare two slopes. Slope angles begin at 0 in the direction of the
+   positive X axis and increase in the direction of the positive Y
+   axis.
+
+   This function always compares the slope vectors based on the
+   smaller angular difference between them, (that is based on an
+   angular difference that is strictly less than pi). To break ties
+   when comparing slope vectors with an angular difference of exactly
+   pi, the vector with a positive dx (or positive dy if dx's are zero)
+   is considered to be more positive than the other.
+
+   Also, all slope vectors with both dx==0 and dy==0 are considered
+   equal and more positive than any non-zero vector.
+
+   <  0 => a less positive than b
+   == 0 => a equal to b
+   >  0 => a more positive than b
+*/
+int
+_cairo_slope_compare (const cairo_slope_t *a, const cairo_slope_t *b)
+{
+    cairo_int64_t ady_bdx = _cairo_int32x32_64_mul (a->dy, b->dx);
+    cairo_int64_t bdy_adx = _cairo_int32x32_64_mul (b->dy, a->dx);
+    int cmp;
+
+    cmp = _cairo_int64_cmp (ady_bdx, bdy_adx);
+    if (cmp)
+	return cmp;
+
+    /* special-case zero vectors.  the intended logic here is:
+     * zero vectors all compare equal, and more positive than any
+     * non-zero vector.
+     */
+    if (a->dx == 0 && a->dy == 0 && b->dx == 0 && b->dy ==0)
+	return 0;
+    if (a->dx == 0 && a->dy == 0)
+	return 1;
+    if (b->dx == 0 && b->dy ==0)
+	return -1;
+
+    /* Finally, we're looking at two vectors that are either equal or
+     * that differ by exactly pi. We can identify the "differ by pi"
+     * case by looking for a change in sign in either dx or dy between
+     * a and b.
+     *
+     * And in these cases, we eliminate the ambiguity by reducing the angle
+     * of b by an infinitesimally small amount, (that is, 'a' will
+     * always be considered less than 'b').
+     */
+    if ((a->dx ^ b->dx) < 0 || (a->dy ^ b->dy) < 0) {
+	if (a->dx > 0 || (a->dx == 0 && a->dy > 0))
+	    return -1;
+	else
+	    return +1;
+    }
+
+    /* Finally, for identical slopes, we obviously return 0. */
+    return 0;
+}