test: Add linear-step-function

Another bug identified by Jeff Muizelaar was that the bounds for a
zero-length (i.e. it started and stopped at the same point) were
miscomputed. This test case exercises that bug.

Note: I believe the output is wrong here when padding a zero-length
gradient. On the left it should be red, and on the right it should be
blue.

test/Makefile.am

@@ -602,6 +602,7 @@ REFERENCE_IMAGES = \
 	linear-gradient.quartz.ref.png \
 	linear-gradient.ref.png \
 	linear-gradient.xlib.ref.png \
+	linear-step-function.xfail.png \
 	linear-uniform.ref.png \
 	long-dashed-lines.ps2.ref.png \
 	long-dashed-lines.ps3.ref.png \

test/Makefile.sources

@@ -128,6 +128,7 @@ test_sources = \
 	line-width-zero.c				\
 	linear-gradient.c				\
 	linear-gradient-reflect.c			\
+	linear-step-function.c				\
 	linear-uniform.c				\
 	long-dashed-lines.c				\
 	long-lines.c					\

test/linear-step-function.c

@@ -0,0 +1,60 @@
+/*
+ * 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"
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    cairo_pattern_t *pattern;
+
+    cairo_set_source_rgb (cr, 0, 0, 0);
+    cairo_paint (cr);
+
+    pattern = cairo_pattern_create_linear (width/2, 0, width/2, 0);
+    cairo_pattern_add_color_stop_rgb (pattern, 0, 1, 0, 0);
+    cairo_pattern_add_color_stop_rgb (pattern, 1, 0, 0, 1);
+    cairo_set_source (cr, pattern);
+
+    cairo_pattern_set_extend (pattern, CAIRO_EXTEND_NONE); /* nothing */
+    cairo_rectangle (cr, 0, 0, width, height/2);
+    cairo_fill (cr);
+
+    cairo_pattern_set_extend (pattern, CAIRO_EXTEND_PAD); /* step */
+    cairo_rectangle (cr, 0, height/2, width, height/2);
+    cairo_fill (cr);
+
+    cairo_pattern_destroy (pattern);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+CAIRO_TEST (linear_step_function,
+	    "Tests creating a step function using a linear gradient",
+	    "gradient, linear", /* keywords */
+	    NULL, /* requirements */
+	    40, 40,
+	    NULL, draw)