Real zero-copy cow snapshotting

The first iteration of COW snapshotting always made an initial copy when
the snapshot was requested (and reused that copy until the surface was
modified). However, in a few circumstances we can avoid even that copy
so long as the surface is still alive and unmodified between the
snapshotting and its use. In order to do so, we need a new proxy surface
that can automatically perform the copy if the target should disappear
prior to use.

1 files changed, 48 insertions, 0 deletions

diff --git a/src/cairo-surface-snapshot-private.h b/src/cairo-surface-snapshot-private.h
new file mode 100644
index 000000000..cbab5458a
--- /dev/null
+++ b/src/cairo-surface-snapshot-private.h
@@ -0,0 +1,48 @@
+/* cairo - a vector graphics library with display and print output
+ *
+ * Copyright © 2009 Intel Corporation
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it either under the terms of the GNU Lesser General Public
+ * License version 2.1 as published by the Free Software Foundation
+ * (the "LGPL") or, at your option, under the terms of the Mozilla
+ * Public License Version 1.1 (the "MPL"). If you do not alter this
+ * notice, a recipient may use your version of this file under either
+ * the MPL or the LGPL.
+ *
+ * You should have received a copy of the LGPL along with this library
+ * in the file COPYING-LGPL-2.1; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ * You should have received a copy of the MPL along with this library
+ * in the file COPYING-MPL-1.1
+ *
+ * The contents of this file are subject to the Mozilla Public License
+ * Version 1.1 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
+ * OF ANY KIND, either express or implied. See the LGPL or the MPL for
+ * the specific language governing rights and limitations.
+ *
+ * The Original Code is the cairo graphics library.
+ *
+ * The Initial Developer of the Original Code is Intel Corporation.
+ *
+ * Contributor(s):
+ *      Chris Wilson <chris@chris-wilson.co.uk>
+ */
+
+#ifndef CAIRO_SURFACE_SNAPSHOT_PRIVATE_H
+#define CAIRO_SURFACE_SNAPSHOT_PRIVATE_H
+
+#include "cairo-surface-private.h"
+
+struct _cairo_surface_snapshot {
+    cairo_surface_t base;
+
+    cairo_surface_t *target;
+    cairo_surface_t *clone;
+};
+
+#endif /* CAIRO_SURFACE_SNAPSHOT_PRIVATE_H */