chromium/cc/layers/viewport.h

// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_LAYERS_VIEWPORT_H_
#define CC_LAYERS_VIEWPORT_H_

#include <memory>

#include "base/gtest_prod_util.h"
#include "base/memory/raw_ptr.h"
#include "cc/layers/layer_impl.h"
#include "ui/gfx/geometry/vector2d_f.h"

namespace cc {

class LayerTreeHostImpl;
struct ScrollNode;

// Encapsulates gesture handling logic on the viewport layers. The "viewport"
// is made up of two scrolling layers, the inner viewport (visual) and the
// outer viewport (layout) scroll layers. These layers have different scroll
// bubbling behavior from the rest of the layer tree which is encoded in this
// class.
//
// When performing any kind of scroll operations on either the inner or outer
// scroll node, they must be done using this class. Typically, the outer
// viewport's scroll node will be used in the scroll chain to represent a full
// viewport scroll (i.e. one that will use this class to scroll both inner and
// outer viewports, as appropriate). However, in some situations (see comments
// in LayerTreeHostImpl::GetNodeToScroll) we may wish to scroll only the inner
// viewport. In that case, the inner viewport is used in the scroll chain, but
// we should still scroll using this class.
class CC_EXPORT Viewport { … };

}  // namespace cc

#endif  // CC_LAYERS_VIEWPORT_H_