test: Add half-coverage to exercise the rasteriser with subpixel geometry.

test/Makefile.sources

@@ -116,6 +116,7 @@ test_sources = \
 	group-clip.c					\
 	group-paint.c					\
 	group-unaligned.c				\
+	half-coverage.c					\
 	huge-linear.c					\
 	huge-radial.c					\
 	image-surface-source.c				\

test/half-coverage.c

@@ -0,0 +1,129 @@
+/*
+ * Copyright 2010 Intel Corporation
+ *
+ * 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: Chris Wilson <chris@chris-wilson.co.uk>
+ */
+
+#include "cairo-test.h"
+
+/* Test the fidelity of the rasterisation, because Cairo is my favourite
+ * driver test suite.
+ */
+
+#define SIZE 256
+#define WIDTH 2
+#define HEIGHT 10
+
+static cairo_test_status_t
+rectangles (cairo_t *cr, int width, int height)
+{
+    int i;
+
+    cairo_set_source_rgb (cr, 1.0, 0.0, 0.0);
+    cairo_paint (cr);
+
+    for (i = 1; i <= SIZE; i++) {
+	int x, y;
+
+	cairo_save (cr);
+	cairo_rectangle (cr, 0, 0, WIDTH, HEIGHT);
+	cairo_clip (cr);
+
+	cairo_scale (cr, 1./SIZE, 1./SIZE);
+	for (x = -i; x < SIZE*WIDTH; x += 2*i) {
+	    for (y = -i; y < SIZE*HEIGHT; y += 2*i) {
+		cairo_rectangle (cr, x, y, i, i);
+		cairo_rectangle (cr, x+i, y+i, i, i);
+	    }
+	}
+	cairo_fill (cr);
+	cairo_restore (cr);
+
+	cairo_translate (cr, WIDTH, 0);
+    }
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+static cairo_test_status_t
+triangles (cairo_t *cr, int width, int height)
+{
+    int i;
+
+    cairo_set_source_rgb (cr, 1.0, 0.0, 0.0);
+    cairo_paint (cr);
+
+    for (i = 1; i <= SIZE; i++) {
+	int x, y;
+
+	cairo_save (cr);
+	cairo_rectangle (cr, 0, 0, WIDTH, HEIGHT);
+	cairo_clip (cr);
+
+	cairo_scale (cr, 1./SIZE, 1./SIZE);
+	for (x = -i; x < SIZE*WIDTH; x += 2*i) {
+	    for (y = -i; y < SIZE*HEIGHT; y += 2*i) {
+		/* add internal edges just for fun */
+		cairo_move_to (cr, x, y);
+		cairo_line_to (cr, x+i, y+i);
+		cairo_line_to (cr, x+i, y);
+		cairo_close_path (cr);
+
+		cairo_move_to (cr, x+i, y);
+		cairo_line_to (cr, x+2*i, y);
+		cairo_line_to (cr, x+i, y+i);
+		cairo_close_path (cr);
+
+		cairo_move_to (cr, x+i, y+i);
+		cairo_line_to (cr, x, y+2*i);
+		cairo_line_to (cr, x+i, y+2*i);
+		cairo_close_path (cr);
+
+		cairo_move_to (cr, x+i, y+i);
+		cairo_line_to (cr, x+i, y+2*i);
+		cairo_line_to (cr, x+2*i, y+2*i);
+		cairo_close_path (cr);
+	    }
+	}
+	cairo_fill (cr);
+	cairo_restore (cr);
+
+	cairo_translate (cr, WIDTH, 0);
+    }
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+CAIRO_TEST (half_coverage_rectangles,
+	    "Check the fidelity of the rasterisation.",
+	    NULL, /* keywords */
+	    "raster", /* requirements */
+	    WIDTH * SIZE, HEIGHT,
+	    NULL, rectangles)
+
+CAIRO_TEST (half_coverage_triangles,
+	    "Check the fidelity of the rasterisation.",
+	    NULL, /* keywords */
+	    "raster", /* requirements */
+	    WIDTH * SIZE, HEIGHT,
+	    NULL, triangles)