Note the changed semantics of cairo_surface_set_device_offset

Specifically, device offsets now affect using the offset surface in
a source pattern as well as drawing to the surface. This behavior
os also verified with a new test case: test/device-offset.c

src/cairo-surface.c

@@ -610,8 +610,8 @@ cairo_surface_mark_dirty_rectangle (cairo_surface_t *surface,
  * sufficient to do this, since functions like
  * cairo_device_to_user() will expose the hidden offset.
  *
- * Note that the offset only affects drawing to the surface, not using
- * the surface in a surface pattern.
+ * Note that the offset affects drawing to the surface as well as
+ * using the surface in a source pattern.
  **/
 void
 cairo_surface_set_device_offset (cairo_surface_t *surface,

test/.gitignore

@@ -22,6 +22,7 @@ dash-caps-joins
 dash-scale
 dash-offset-negative
 dash-zero-length
+device-offset
 extend-reflect
 fallback-resolution
 fallback-resolution.pdf

test/Makefile.am

@@ -19,6 +19,7 @@ dash-caps-joins			\
 dash-scale			\
 dash-offset-negative		\
 dash-zero-length		\
+device-offset			\
 extend-reflect			\
 fallback-resolution		\
 fill-and-stroke			\

test/device-offset.c

@@ -0,0 +1,93 @@
+/*
+ * Copyright © 2006 Red Hat, Inc.
+ *
+ * Permission to use, copy, modify, distribute, and sell this software
+ * and its documentation for any purpose is hereby granted without
+ * fee, provided that the above copyright notice appear in all copies
+ * and that both that copyright notice and this permission notice
+ * appear in supporting documentation, and that the name of
+ * Red Hat, Inc. not be used in advertising or publicity pertaining to
+ * distribution of the software without specific, written prior
+ * permission. Red Hat, Inc. makes no representations about the
+ * suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * RED HAT, INC. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
+ * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS, IN NO EVENT SHALL RED HAT, INC. BE LIABLE FOR ANY SPECIAL,
+ * INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
+ * RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
+ * IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * Author: Carl D. Worth <cworth@cworth.org>
+ */
+
+#include "cairo-test.h"
+#include <stddef.h>
+
+#define SIZE 10
+#define PAD 2
+
+cairo_test_t test = {
+    "device-offset",
+    "Simple test using a surface with a device-offset as a source.",
+    SIZE, SIZE
+};
+
+static void
+draw_square (cairo_t *cr)
+{
+    cairo_rectangle (cr,
+		     PAD, PAD,
+		     SIZE - 2 * PAD,
+		     SIZE - 2 * PAD);
+    cairo_fill (cr);
+}
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    cairo_surface_t *surface, *target;
+    cairo_t *cr2;
+
+    /* First draw a shape in black on the original destination. */
+    cairo_set_source_rgb (cr, 0, 0, 1); /* blue */
+    draw_square (cr);
+
+    cairo_surface_write_to_png (cairo_get_target (cr), "/tmp/a.png");
+
+    /* Then, create an offset surface and repeat the drawing in red. */
+    target = cairo_get_target (cr);
+    surface = cairo_surface_create_similar (target,
+					    cairo_surface_get_content (target),
+					    SIZE / 2, SIZE / 2);
+    cairo_surface_set_device_offset (surface, - SIZE / 2, - SIZE / 2);
+    cr2 = cairo_create (surface);
+
+    cairo_set_source_rgb (cr2, 1, 0, 0); /* red */
+    draw_square (cr2);
+
+    cairo_surface_write_to_png (surface, "/tmp/b.png");
+
+    cairo_destroy (cr2);
+
+    /* Finally, copy the offset surface to the original destination.
+    * The final result should be a blue square with the lower-right
+    * quarter red. */
+    cairo_set_source_surface (cr, surface, 0, 0);
+
+    cairo_paint (cr);
+
+    cairo_surface_write_to_png (cairo_get_target (cr), "/tmp/c.png");
+
+    cairo_surface_destroy (surface);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+int
+main (void)
+{
+    return cairo_test (&test, draw);
+}