Imported Upstream version 1.12.4upstream/1.12.4

1 files changed, 120 insertions, 0 deletions

diff --git a/test/bug-seams.c b/test/bug-seams.c
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+++ b/test/bug-seams.c
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+/*
+ * Copyright 2010 Soeren Sandmann Pedersen
+ *
+ * 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: Soeren Sandmann <sandmann@daimi.au.dk>
+ */
+
+/* Exercises a case of seam appearing between two polygons in the image
+ * backend but not in xlib [using pixman].
+ *
+ * The test case draws two abutting quads both individually on the
+ * leftm combining them with operator ADD, and in one go on the right.
+ * Both methods should show no signs of seaming at the common edge
+ * between the two quads, but the individually drawn ones have a
+ * slight seam.
+ *
+ * The cause of the seam is that there are slight differences in the
+ * output of the analytical coverage rasterization and the
+ * supersampling rasterization methods, both employed by
+ * cairo-tor-scan-converter.  When drawn individually, the scan
+ * converter gets a partial view of the geometry at a time, so it ends
+ * up making different decisions about which scanlines it rasterizes
+ * with which method, compared to when the geometry is draw all at
+ * once.  Though both methods produce seamless results individually
+ * (where applicable), they don't produce bit-exact identical results,
+ * and hence we get seaming where they meet.
+ */
+
+#include "cairo-test.h"
+
+static void
+draw_quad (cairo_t *cr,
+	   double x1, double y1, double x2, double y2,
+	   double x3, double y3, double x4, double y4)
+{
+    cairo_move_to (cr, x1, y1);
+    cairo_line_to (cr, x2, y2);
+    cairo_line_to (cr, x3, y3);
+    cairo_line_to (cr, x4, y4);
+    cairo_close_path (cr);
+}
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    cairo_set_source_rgb (cr, 0, 0, 0);
+    cairo_paint (cr);
+
+    cairo_scale (cr, 20, 20);
+    cairo_translate (cr, 5, 1);
+
+    /* On the left side, we have two quads drawn one at a time and
+     * combined with OPERATOR_ADD.  This should be seamless, but
+     * isn't. */
+    cairo_push_group (cr);
+    cairo_set_operator (cr, CAIRO_OPERATOR_ADD);
+
+    cairo_set_source_rgb (cr, 0, 0.6, 0);
+    draw_quad (cr,
+	       1.50, 1.50,
+	       2.64, 1.63,
+	       1.75, 2.75,
+	       0.55, 2.63);
+    cairo_fill (cr);
+    draw_quad (cr,
+	       0.55, 2.63,
+	       1.75, 2.75,
+	       0.98, 4.11,
+	       -0.35, 4.05);
+    cairo_fill (cr);
+
+    cairo_pop_group_to_source (cr);
+    cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
+    cairo_paint (cr);
+
+    /* On the right side, we have the same two quads drawn both at the
+     * same time.  This is seamless. */
+    cairo_translate (cr, 10, 0);
+
+    cairo_set_source_rgb (cr, 0, 0.6, 0);
+    draw_quad (cr,
+	       1.50, 1.50,
+	       2.64, 1.63,
+	       1.75, 2.75,
+	       0.55, 2.63);
+    draw_quad (cr,
+	       0.55, 2.63,
+	       1.75, 2.75,
+	       0.98, 4.11,
+	       -0.35, 4.05);
+    cairo_fill (cr);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+CAIRO_TEST (bug_seams,
+	    "Check the fidelity of the rasterisation.",
+	    "raster", /* keywords */
+	    "target=raster", /* requirements */
+	    500, 300,
+	    NULL, draw)