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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=8 et :
+ */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_layers_Composer2D_h
+#define mozilla_layers_Composer2D_h
+
+#include "gfxTypes.h"
+#include "nsISupportsImpl.h"
+
+/**
+ * Many platforms have dedicated hardware for simple composition.
+ * This hardware is usually faster or more power efficient than the
+ * GPU. However, in exchange for this better performance, generality
+ * has to be sacrificed: no 3d transforms, no intermediate surfaces,
+ * no special shader effects, loss of other goodies depending on the
+ * platform.
+ *
+ * Composer2D is a very simple interface to this class of hardware
+ * that allows an implementation to "try rendering" with the fast
+ * path. If the given layer tree requires more generality than the
+ * hardware provides, the implementation should bail and have the
+ * layer manager fall back on full GPU composition.
+ */
+
+class nsIWidget;
+
+namespace mozilla {
+namespace layers {
+
+class Layer;
+
+class Composer2D {
+ NS_INLINE_DECL_THREADSAFE_REFCOUNTING(Composer2D)
+
+protected:
+ // Protected destructor, to discourage deletion outside of Release():
+ virtual ~Composer2D() {}
+
+public:
+ /**
+ * Return true if |aRoot| met the implementation's criteria for fast
+ * composition and the render was successful. Return false to fall
+ * back on the GPU.
+ *
+ * Currently, when TryRender() returns true, the entire framebuffer
+ * must have been rendered.
+ */
+ virtual bool TryRenderWithHwc(Layer* aRoot,
+ nsIWidget* aWidget,
+ bool aGeometryChanged,
+ bool aHasImageHostOverlays) = 0;
+
+ /**
+ * Return true if Composer2D does composition. Return false if Composer2D
+ * failed the composition.
+ */
+ virtual bool Render(nsIWidget* aWidget) = 0;
+
+ /**
+ * Return true if Composer2D has a fast composition hardware.
+ * Return false if Composer2D does not have a fast composition hardware.
+ */
+ virtual bool HasHwc() = 0;
+};
+
+} // namespace layers
+} // namespace mozilla
+
+#endif // mozilla_layers_Composer2D_h