gecko/content/events/src/nsDOMDataTransfer.h

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#ifndef nsDOMDataTransfer_h__
#define nsDOMDataTransfer_h__

#include "nsString.h"
#include "nsTArray.h"
#include "nsIVariant.h"
#include "nsIPrincipal.h"
#include "nsIDOMDataTransfer.h"
#include "nsIDragService.h"
#include "nsIDOMElement.h"
#include "nsCycleCollectionParticipant.h"

#include "nsAutoPtr.h"
#include "nsIFile.h"
#include "nsILocalFile.h"
#include "nsDOMFile.h"

class nsITransferable;

/**
 * TransferItem is used to hold data for a particular format. Each piece of
 * data has a principal set from the caller which added it. This allows a
 * caller that wishes to retrieve the data to only be able to access the data
 * it is allowed to, yet still allow a chrome caller to retrieve any of the
 * data.
 */
struct TransferItem {
  nsString mFormat;
  nsCOMPtr<nsIPrincipal> mPrincipal;
  nsCOMPtr<nsIVariant> mData;
};

class nsDOMDataTransfer : public nsIDOMDataTransfer,
                          public nsIDOMNSDataTransfer
{
public:
  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
  NS_DECL_NSIDOMDATATRANSFER
  NS_DECL_NSIDOMNSDATATRANSFER

  NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(nsDOMDataTransfer, nsIDOMDataTransfer)

  friend class nsDOMDragEvent;
  friend class nsEventStateManager;
  friend class nsContentUtils;

protected:

  // the constructors are protected so only our friends can call them

  // default constructor used for the dragstart/draggesture event and
  // synthetic events
  nsDOMDataTransfer();

  // this constructor must only be used to create a dataTransfer for a drag
  // that was started without using a data transfer, either an external drag,
  // that is, a drag where the source is another application, or a drag
  // started by calling the drag service directly.
  nsDOMDataTransfer(PRUint32 aEventType);

  // this constructor is used only by the Clone method to copy the fields as
  // needed to a new data transfer.
  nsDOMDataTransfer(PRUint32 aEventType,
                    const PRUint32 aEffectAllowed,
                    bool aCursorState,
                    bool aIsExternal,
                    bool aUserCancelled,
                    nsTArray<nsTArray<TransferItem> >& aItems,
                    nsIDOMElement* aDragImage,
                    PRUint32 aDragImageX,
                    PRUint32 aDragImageY);

  static const char sEffects[8][9];

public:

  void GetDragTarget(nsIDOMElement** aDragTarget)
  {
    *aDragTarget = mDragTarget;
    NS_IF_ADDREF(*aDragTarget);
  }

  // a readonly dataTransfer cannot have new data added or existing data removed.
  // Only the dropEffect and effectAllowed may be modified.
  void SetReadOnly() { mReadOnly = PR_TRUE; }

  // converts the data into an array of nsITransferable objects to be used for
  // drag and drop or clipboard operations.
  void GetTransferables(nsISupportsArray** transferables);

  // converts the data in the variant to an nsISupportString if possible or
  // an nsISupports or null otherwise.
  bool ConvertFromVariant(nsIVariant* aVariant,
                            nsISupports** aSupports,
                            PRUint32* aLength);

  // clears all of the data
  void ClearAll();

  // Similar to SetData except also specifies the principal to store.
  // aData may be null when called from CacheExternalFormats.
  nsresult SetDataWithPrincipal(const nsAString& aFormat,
                                nsIVariant* aData,
                                PRUint32 aIndex,
                                nsIPrincipal* aPrincipal);

protected:

  // returns a weak reference to the drag image
  nsIDOMElement* GetDragImage(PRInt32* aX, PRInt32* aY)
  {
    *aX = mDragImageX;
    *aY = mDragImageY;
    return mDragImage;
  }

  // returns a weak reference to the current principal
  nsIPrincipal* GetCurrentPrincipal(nsresult* rv);

  // converts some formats used for compatibility in aInFormat into aOutFormat.
  // Text and text/unicode become text/plain, and URL becomes text/uri-list
  void GetRealFormat(const nsAString& aInFormat, nsAString& aOutFormat);

  // caches the formats that exist in the drag service that were added by an
  // external drag
  void CacheExternalFormats();

  // fills in the data field of aItem with the data from the drag service for
  // a given index.
  void FillInExternalDragData(TransferItem& aItem, PRUint32 aIndex);

  // the event type this data transfer is for. This will correspond to an
  // event->message value.
  PRUint32 mEventType;

  // the drop effect and effect allowed
  PRUint32 mDropEffect;
  PRUint32 mEffectAllowed;

  // Indicates the behavior of the cursor during drag operations
  bool mCursorState;

  // readonly data transfers may not be modified except the drop effect and
  // effect allowed.
  bool mReadOnly;

  // true for drags started without a data transfer, for example, those from
  // another application.
  bool mIsExternal;

  // true if the user cancelled the drag. Used only for the dragend event.
  bool mUserCancelled;

  // array of items, each containing an array of format->data pairs
  nsTArray<nsTArray<TransferItem> > mItems;

  // array of files, containing only the files present in the dataTransfer
  nsRefPtr<nsDOMFileList> mFiles;

  // the target of the drag. The drag and dragend events will fire at this.
  nsCOMPtr<nsIDOMElement> mDragTarget;

  // the custom drag image and coordinates within the image. If mDragImage is
  // null, the default image is created from the drag target.
  nsCOMPtr<nsIDOMElement> mDragImage;
  PRUint32 mDragImageX;
  PRUint32 mDragImageY;
};

#endif // nsDOMDataTransfer_h__