test: Add rectilinear-grid

The rectilinear scan converter assumes disjoint rects as input, but
cairo-image passes intersecting rectangles to it.

This test shows that image and any backends passing through it for the
rasterization (fallbacks, vector backends whose renderer is
cairo-based) fail in compute the corners of intersecting rectangles
correctly.

1 files changed, 78 insertions, 0 deletions

diff --git a/test/rectilinear-grid.c b/test/rectilinear-grid.c
new file mode 100644
index 000000000..1baadf732
--- /dev/null
+++ b/test/rectilinear-grid.c
@@ -0,0 +1,78 @@
+/* -*- Mode: c; c-basic-offset: 4; indent-tabs-mode: t; tab-width: 8; -*- */
+/*
+ * Copyright 2010 Andrea Canciani
+ *
+ * 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: Andrea Canciani <ranma42@gmail.com>
+ */
+
+#include "cairo-test.h"
+
+#define SIZE 52
+#define OFFSET 5
+#define DISTANCE 10.25
+
+/*
+  This test checks that boxes not aligned to pixels are drawn
+  correctly.
+
+  In particular the corners of the boxes are drawn incorrectly by
+  cairo-image in cairo 1.10.0, because overlapping boxes are passed to
+  a span converter which assumes disjoint boxes as input.
+
+  This results in corners to be drawn with the wrong shade.
+*/
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    int i;
+
+    cairo_set_source_rgb (cr, 1, 1, 1);
+    cairo_paint (cr);
+
+    cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
+    cairo_set_source_rgb (cr, 0, 0, 0);
+    cairo_set_line_width (cr, 4);
+    cairo_translate (cr, 2*OFFSET, 2*OFFSET);
+
+    for (i = 0; i < 4; i++) {
+	double x = i * DISTANCE;
+
+	cairo_move_to (cr, x, -OFFSET-0.75);
+	cairo_line_to (cr, x, SIZE-3*OFFSET-0.25);
+
+	cairo_move_to (cr, -OFFSET-0.75, x);
+	cairo_line_to (cr, SIZE-3*OFFSET-0.25, x);
+    }
+
+    cairo_stroke (cr);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+CAIRO_TEST (rectilinear_grid,
+	    "Test rectilinear rasterizer (covering partial pixels)",
+	    "rectilinear", /* keywords */
+	    NULL, /* requirements */
+	    SIZE, SIZE,
+	    NULL, draw)