text: // Copyright 2017 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef COMPONENTS_EXO_DATA_DEVICE_H_
  #define COMPONENTS_EXO_DATA_DEVICE_H_
  
  #include <cstdint>
  
  #include "base/macros.h"
  #include "components/exo/data_offer_observer.h"
  #include "components/exo/seat_observer.h"
  #include "components/exo/surface.h"
  #include "components/exo/surface_observer.h"
  #include "components/exo/wm_helper.h"
  #include "ui/base/clipboard/clipboard_observer.h"
  
  namespace ui {
  class DropTargetEvent;
  }
  
  namespace exo {
  
  class DataDeviceDelegate;
  class DataOffer;
  class DataSource;
  class FileHelper;
  class Seat;
  
  enum class DndAction { kNone, kCopy, kMove, kAsk };
  
  class ScopedDataOffer;
  class ScopedSurface;
  
  // DataDevice to start drag and drop and copy and paste oprations.
  class DataDevice : public WMHelper::DragDropObserver,
                     public DataOfferObserver,
                     public ui::ClipboardObserver,
                     public SurfaceObserver,
                     public SeatObserver {
   public:
    explicit DataDevice(DataDeviceDelegate* delegate,
                        Seat* seat,
                        FileHelper* file_helper);
    ~DataDevice() override;
  
    // Starts drag-and-drop operation.
    // |source| represents data comes from the client starting drag operation. Can
    // be null if the data will be transferred only in the client.  |origin| is
    // the surface which starts the drag and drop operation. |icon| is the
    // nullable image which is rendered at the next to cursor while drag
    // operation. |serial| is the unique number comes from input events which
    // triggers the drag and drop operation.
    void StartDrag(const DataSource* source,
                   Surface* origin,
                   Surface* icon,
                   uint32_t serial);
  
    // Sets selection data to the clipboard.
    // |source| represents data comes from the client. |serial| is the unique
    // number comes from input events which triggers the drag and drop operation.
    void SetSelection(DataSource* source, uint32_t serial);
  
    // Overridden from WMHelper::DragDropObserver:
    void OnDragEntered(const ui::DropTargetEvent& event) override;
    int OnDragUpdated(const ui::DropTargetEvent& event) override;
    void OnDragExited() override;
    int OnPerformDrop(const ui::DropTargetEvent& event) override;
  
    // Overridden from ui::ClipbaordObserver:
    void OnClipboardDataChanged() override;
  
    // Overridden from SeatObserver:
    void OnSurfaceFocusing(Surface* surface) override;
    void OnSurfaceFocused(Surface* surface) override;
  
    // Overridden from DataOfferObserver:
    void OnDataOfferDestroying(DataOffer* data_offer) override;
  
    // Overridden from SurfaceObserver:
    void OnSurfaceDestroying(Surface* surface) override;
  
   private:
    Surface* GetEffectiveTargetForEvent(const ui::DropTargetEvent& event) const;
    void SetSelectionToCurrentClipboardData();
  
    DataDeviceDelegate* const delegate_;
    Seat* const seat_;
    FileHelper* const file_helper_;
    std::unique_ptr<ScopedDataOffer> data_offer_;
    std::unique_ptr<ScopedSurface> focused_surface_;
  
    DISALLOW_COPY_AND_ASSIGN(DataDevice);
  };
  
  }  // namespace exo
  
  #endif  // COMPONENTS_EXO_DATA_DEVICE_H_
  