/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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_FocusTarget_h
#define mozilla_layers_FocusTarget_h

#include <stdint.h> // for int32_t, uint32_t

#include "FrameMetrics.h"        // for FrameMetrics::ViewID
#include "mozilla/DefineEnum.h"  // for MOZ_DEFINE_ENUM
#include "mozilla/Variant.h"     // for Variant

class nsIPresShell;

namespace mozilla {
namespace layers {

/**
 * This class is used for communicating information about the currently focused
 * element of a document and the scrollable frames to use when keyboard scrolling
 * it. It is created on the main thread at paint-time, but is then passed over
 * IPC to the compositor/APZ code.
 */
class FocusTarget final
{
public:
  struct ScrollTargets
  {
    FrameMetrics::ViewID mHorizontal;
    FrameMetrics::ViewID mVertical;

    bool operator==(const ScrollTargets& aRhs) const
    {
      return mHorizontal == aRhs.mHorizontal &&
             mVertical == aRhs.mVertical;
    }
  };

  typedef uint64_t RefLayerId;

  // We need this to represent the case where mData has no focus target data
  // because we can't have an empty variant
  struct NoFocusTarget {
    bool operator==(const NoFocusTarget& aRhs) const
    {
     return true;
    }
  };

  FocusTarget();

  /**
   * Construct a focus target for the specified top level PresShell
   */
  FocusTarget(nsIPresShell* aRootPresShell,
              uint64_t aFocusSequenceNumber);

  bool operator==(const FocusTarget& aRhs) const;

public:
  // The content sequence number recorded at the time of this class's creation
  uint64_t mSequenceNumber;

  // Whether there are keydown, keypress, or keyup event listeners
  // in the event target chain of the focused element
  bool mFocusHasKeyEventListeners;

  mozilla::Variant<RefLayerId, ScrollTargets, NoFocusTarget> mData;
};

} // namespace layers
} // namespace mozilla

#endif // mozilla_layers_FocusTarget_h
