1 files changed, 83 insertions, 0 deletions
diff --git a/libs/cairo-1.16.0/test/dash-infinite-loop.c b/libs/cairo-1.16.0/test/dash-infinite-loop.c
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+++ b/libs/cairo-1.16.0/test/dash-infinite-loop.c
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+/*
+ * Copyright © 2009 M Joonas Pihlaja
+ *
+ * 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: M Joonas Pihlaja <jpihlaja@cc.helsinki.fi>
+ */
+
+#include "cairo-test.h"
+
+/* When faced with very small dash lengths the stroker is liable to
+ * get stuck in an infinite loop when advancing the dash offset.  This
+ * test attempts to hit each of the locations in the stroker code
+ * where the dash offset is advanced in a loop.
+ *
+ * Reported to the cairo mailing list by Hans Breuer.
+ * https://lists.cairographics.org/archives/cairo/2009-June/017506.html
+ */
+
+#define EPS 1e-30
+/* This should be comfortably smaller than the unit epsilon of the
+ * floating point type used to advance the dashing, yet not small
+ * enough that it underflows to zero.  1e-30 works to foil up to 80
+ * bit extended precision arithmetic.  We want to avoid zero dash
+ * lengths because those trigger special processing in the stroker. */
+
+static void
+do_dash (cairo_t *cr, double dx, double dy, double offset)
+{
+    /* Set the dash pattern to be predominantly ON so that we can
+     * create a reference image by just ignoring the dashing. */
+    static double dash[] = { EPS, EPS/512 };
+    cairo_set_dash (cr, dash, 2, offset);
+    cairo_move_to (cr, 10, 10);
+    cairo_rel_line_to (cr, dx, dy);
+    cairo_stroke (cr);
+    cairo_translate (cr, dx, dy);
+}
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    (void)width; (void)height;
+
+    cairo_set_source_rgb (cr, 1,1,1);
+    cairo_paint (cr);
+    cairo_set_source_rgb (cr, 0,0,0);
+
+    cairo_set_line_width (cr, 10);
+
+    /* The following calls will wedge in various places that try
+     * to advance the dashing in a loop inside the stroker. */
+    do_dash (cr, 30, 30, 0); /* _cairo_stroker_line_to_dashed */
+    do_dash (cr, 30,  0, 0); /* _cairo_rectilinear_stroker_line_to_dashed */
+    do_dash (cr, 30, 30, 1); /* _cairo_stroker_dash_start */
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+CAIRO_TEST (dash_infinite_loop,
+            "Test dashing with extremely small dash lengths.",
+            "dash",
+            NULL,
+            100, 100,
+            NULL, draw);