/* -*- Mode: C++; tab-width: 2; 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 nsEventStateManager_h__
#define nsEventStateManager_h__

#include "mozilla/TypedEnum.h"

#include "nsEvent.h"
#include "nsGUIEvent.h"
#include "nsIObserver.h"
#include "nsWeakReference.h"
#include "nsITimer.h"
#include "nsCOMPtr.h"
#include "nsCOMArray.h"
#include "nsIFrameLoader.h"
#include "nsCycleCollectionParticipant.h"
#include "nsIMarkupDocumentViewer.h"
#include "nsIScrollableFrame.h"
#include "nsFocusManager.h"
#include "nsEventStates.h"
#include "mozilla/TimeStamp.h"
#include "nsIFrame.h"

class nsIPresShell;
class nsIContent;
class nsIDocument;
class nsIDocShell;
class nsIDocShellTreeNode;
class nsIDocShellTreeItem;
class imgIContainer;
class nsDOMDataTransfer;
class MouseEnterLeaveDispatcher;
class nsIFrame;

namespace mozilla {
namespace dom {
class TabParent;
}
}

/*
 * Event listener manager
 */

class nsEventStateManager : public nsSupportsWeakReference,
                            public nsIObserver
{
  friend class nsMouseWheelTransaction;
public:

  typedef mozilla::TimeStamp TimeStamp;
  typedef mozilla::TimeDuration TimeDuration;

  nsEventStateManager();
  virtual ~nsEventStateManager();

  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
  NS_DECL_NSIOBSERVER

  nsresult Init();
  nsresult Shutdown();

  /* The PreHandleEvent method is called before event dispatch to either
   * the DOM or frames.  Any processing which must not be prevented or
   * cancelled should occur here.  Any processing which is intended to
   * be conditional based on either DOM or frame processing should occur in
   * PostHandleEvent.  Any centralized event processing which must occur before
   * DOM or frame event handling should occur here as well.
   */
  nsresult PreHandleEvent(nsPresContext* aPresContext,
                          nsEvent *aEvent,
                          nsIFrame* aTargetFrame,
                          nsEventStatus* aStatus);

  /* The PostHandleEvent method should contain all system processing which
   * should occur conditionally based on DOM or frame processing.  It should
   * also contain any centralized event processing which must occur after
   * DOM and frame processing.
   */
  nsresult PostHandleEvent(nsPresContext* aPresContext,
                           nsEvent *aEvent,
                           nsIFrame* aTargetFrame,
                           nsEventStatus* aStatus);

  /**
   * DispatchLegacyMouseScrollEvents() dispatches NS_MOUSE_SCROLL event and
   * NS_MOUSE_PIXEL_SCROLL event for compatiblity with old Goanna.
   */
  void DispatchLegacyMouseScrollEvents(nsIFrame* aTargetFrame,
                                       mozilla::widget::WheelEvent* aEvent,
                                       nsEventStatus* aStatus);

  void NotifyDestroyPresContext(nsPresContext* aPresContext);
  void SetPresContext(nsPresContext* aPresContext);
  void ClearFrameRefs(nsIFrame* aFrame);

  nsIFrame* GetEventTarget();
  already_AddRefed<nsIContent> GetEventTargetContent(nsEvent* aEvent);

  /**
   * Notify that the given NS_EVENT_STATE_* bit has changed for this content.
   * @param aContent Content which has changed states
   * @param aState   Corresponding state flags such as NS_EVENT_STATE_FOCUS
   * @return  Whether the content was able to change all states. Returns false
   *                  if a resulting DOM event causes the content node passed in
   *                  to not change states. Note, the frame for the content may
   *                  change as a result of the content state change, because of
   *                  frame reconstructions that may occur, but this does not
   *                  affect the return value.
   */
  bool SetContentState(nsIContent *aContent, nsEventStates aState);
  void ContentRemoved(nsIDocument* aDocument, nsIContent* aContent);
  bool EventStatusOK(nsGUIEvent* aEvent);

  /**
   * Register accesskey on the given element. When accesskey is activated then
   * the element will be notified via nsIContent::PerformAccesskey() method.
   *
   * @param  aContent  the given element
   * @param  aKey      accesskey
   */
  void RegisterAccessKey(nsIContent* aContent, uint32_t aKey);

  /**
   * Unregister accesskey for the given element.
   *
   * @param  aContent  the given element
   * @param  aKey      accesskey
   */
  void UnregisterAccessKey(nsIContent* aContent, uint32_t aKey);

  /**
   * Get accesskey registered on the given element or 0 if there is none.
   *
   * @param  aContent  the given element (must not be null)
   * @return           registered accesskey
   */
  uint32_t GetRegisteredAccessKey(nsIContent* aContent);

  bool GetAccessKeyLabelPrefix(nsAString& aPrefix);

  nsresult SetCursor(int32_t aCursor, imgIContainer* aContainer,
                     bool aHaveHotspot, float aHotspotX, float aHotspotY,
                     nsIWidget* aWidget, bool aLockCursor); 

  static void StartHandlingUserInput()
  {
    ++sUserInputEventDepth;
    if (sUserInputEventDepth == 1) {
      sHandlingInputStart = TimeStamp::Now();
    }
  }

  static void StopHandlingUserInput()
  {
    --sUserInputEventDepth;
    if (sUserInputEventDepth == 0) {
      sHandlingInputStart = TimeStamp();
    }
  }

  /**
   * Returns true if the current code is being executed as a result of user input.
   * This includes timers or anything else that is initiated from user input.
   * However, mouse over events are not counted as user input, nor are
   * page load events. If this method is called from asynchronously executed code,
   * such as during layout reflows, it will return false. If more time has elapsed
   * since the user input than is specified by the
   * dom.event.handling-user-input-time-limit pref (default 1 second), this
   * function also returns false.
   */
  static bool IsHandlingUserInput();

  nsPresContext* GetPresContext() { return mPresContext; }

  NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(nsEventStateManager,
                                           nsIObserver)

  static nsIDocument* sMouseOverDocument;

  static nsEventStateManager* GetActiveEventStateManager() { return sActiveESM; }

  // Sets aNewESM to be the active event state manager, and
  // if aContent is non-null, marks the object as active.
  static void SetActiveManager(nsEventStateManager* aNewESM,
                               nsIContent* aContent);

  // Sets the full-screen event state on aElement to aIsFullScreen.
  static void SetFullScreenState(mozilla::dom::Element* aElement, bool aIsFullScreen);

  static bool IsRemoteTarget(nsIContent* aTarget);
  static nsIntPoint GetChildProcessOffset(nsFrameLoader* aFrameLoader,
                                          const nsEvent& aEvent);

  static void MapEventCoordinatesForChildProcess(nsFrameLoader* aFrameLoader,
                                                 nsEvent* aEvent);

  static void MapEventCoordinatesForChildProcess(const nsIntPoint& aOffset,
                                                 nsEvent* aEvent);

  // Holds the point in screen coords that a mouse event was dispatched to,
  // before we went into pointer lock mode. This is constantly updated while
  // the pointer is not locked, but we don't update it while the pointer is
  // locked. This is used by nsDOMEvent::GetScreenCoords() to make mouse
  // events' screen coord appear frozen at the last mouse position while
  // the pointer is locked.
  static nsIntPoint sLastScreenPoint;

  // Holds the point in client coords of the last mouse event. Used by
  // nsDOMEvent::GetClientCoords() to make mouse events' client coords appear
  // frozen at the last mouse position while the pointer is locked.
  static nsIntPoint sLastClientPoint;

  static bool sIsPointerLocked;
  static nsWeakPtr sPointerLockedElement;
  static nsWeakPtr sPointerLockedDoc;

protected:
  friend class MouseEnterLeaveDispatcher;

  void UpdateCursor(nsPresContext* aPresContext, nsEvent* aEvent, nsIFrame* aTargetFrame, nsEventStatus* aStatus);
  /**
   * Turn a GUI mouse event into a mouse event targeted at the specified
   * content.  This returns the primary frame for the content (or null
   * if it goes away during the event).
   */
  nsIFrame* DispatchMouseEvent(nsGUIEvent* aEvent, uint32_t aMessage,
                               nsIContent* aTargetContent,
                               nsIContent* aRelatedContent);
  /**
   * Synthesize DOM and frame mouseover and mouseout events from this
   * MOUSE_MOVE or MOUSE_EXIT event.
   */
  void GenerateMouseEnterExit(nsGUIEvent* aEvent);
  /**
   * Tell this ESM and ESMs in parent documents that the mouse is
   * over some content in this document.
   */
  void NotifyMouseOver(nsGUIEvent* aEvent, nsIContent* aContent);
  /**
   * Tell this ESM and ESMs in affected child documents that the mouse
   * has exited this document's currently hovered content.
   * @param aEvent the event that triggered the mouseout
   * @param aMovingInto the content node we've moved into.  This is used to set
   *        the relatedTarget for mouseout events.  Also, if it's non-null
   *        NotifyMouseOut will NOT change the current hover content to null;
   *        in that case the caller is responsible for updating hover state.
   */
  void NotifyMouseOut(nsGUIEvent* aEvent, nsIContent* aMovingInto);
  void GenerateDragDropEnterExit(nsPresContext* aPresContext, nsGUIEvent* aEvent);
  /**
   * Fire the dragenter and dragexit/dragleave events when the mouse moves to a
   * new target.
   *
   * @param aRelatedTarget relatedTarget to set for the event
   * @param aTargetContent target to set for the event
   * @param aTargetFrame target frame for the event
   */
  void FireDragEnterOrExit(nsPresContext* aPresContext,
                           nsGUIEvent* aEvent,
                           uint32_t aMsg,
                           nsIContent* aRelatedTarget,
                           nsIContent* aTargetContent,
                           nsWeakFrame& aTargetFrame);
  /**
   * Update the initial drag session data transfer with any changes that occur
   * on cloned data transfer objects used for events.
   */
  void UpdateDragDataTransfer(nsDragEvent* dragEvent);

  nsresult SetClickCount(nsPresContext* aPresContext, nsMouseEvent *aEvent, nsEventStatus* aStatus);
  nsresult CheckForAndDispatchClick(nsPresContext* aPresContext, nsMouseEvent *aEvent, nsEventStatus* aStatus);
  void EnsureDocument(nsPresContext* aPresContext);
  void FlushPendingEvents(nsPresContext* aPresContext);

  /**
   * The phases of HandleAccessKey processing. See below.
   */
  typedef enum {
    eAccessKeyProcessingNormal = 0,
    eAccessKeyProcessingUp,
    eAccessKeyProcessingDown
  } ProcessingAccessKeyState;

  /**
   * Access key handling.  If there is registered content for the accesskey
   * given by the key event and modifier mask then call
   * content.PerformAccesskey(), otherwise call HandleAccessKey() recursively,
   * on descendant docshells first, then on the ancestor (with |aBubbledFrom|
   * set to the docshell associated with |this|), until something matches.
   *
   * @param aPresContext the presentation context
   * @param aEvent the key event
   * @param aStatus the event status
   * @param aBubbledFrom is used by an ancestor to avoid calling HandleAccessKey()
   *        on the child the call originally came from, i.e. this is the child
   *        that recursively called us in its Up phase. The initial caller
   *        passes |nullptr| here. This is to avoid an infinite loop.
   * @param aAccessKeyState Normal, Down or Up processing phase (see enums
   *        above). The initial event receiver uses 'normal', then 'down' when
   *        processing children and Up when recursively calling its ancestor.
   * @param aModifierMask modifier mask for the key event
   */
  void HandleAccessKey(nsPresContext* aPresContext,
                       nsKeyEvent* aEvent,
                       nsEventStatus* aStatus,
                       nsIDocShellTreeItem* aBubbledFrom,
                       ProcessingAccessKeyState aAccessKeyState,
                       int32_t aModifierMask);

  bool ExecuteAccessKey(nsTArray<uint32_t>& aAccessCharCodes,
                          bool aIsTrustedEvent);

  //---------------------------------------------
  // DocShell Focus Traversal Methods
  //---------------------------------------------

  nsIContent* GetFocusedContent();
  bool IsShellVisible(nsIDocShell* aShell);

  // These functions are for mousewheel and pixel scrolling

  class WheelPrefs
  {
  public:
    static WheelPrefs* GetInstance();
    static void Shutdown();

    /**
     * ApplyUserPrefsToDelta() overrides the wheel event's delta values with
     * user prefs.
     */
    void ApplyUserPrefsToDelta(mozilla::widget::WheelEvent* aEvent);

    /**
     * If ApplyUserPrefsToDelta() changed the delta values with customized
     * prefs, the overflowDelta values would be inflated.
     * CancelApplyingUserPrefsFromOverflowDelta() cancels the inflation.
     */
    void CancelApplyingUserPrefsFromOverflowDelta(
                                    mozilla::widget::WheelEvent* aEvent);

    /**
     * Computes the default action for the aEvent with the prefs.
     */
    enum Action MOZ_ENUM_TYPE(uint8_t)
    {
      ACTION_NONE = 0,
      ACTION_SCROLL,
      ACTION_HISTORY,
      ACTION_ZOOM,
      ACTION_HSCROLL,
      ACTION_LAST = ACTION_HSCROLL
    };
    Action ComputeActionFor(mozilla::widget::WheelEvent* aEvent);

    /**
     * NeedToComputeLineOrPageDelta() returns if the aEvent needs to be
     * computed the lineOrPageDelta values.
     */
    bool NeedToComputeLineOrPageDelta(mozilla::widget::WheelEvent* aEvent);

    /**
     * IsOverOnePageScrollAllowed*() checks whether wheel scroll amount should
     * be rounded down to the page width/height (false) or not (true).
     */
    bool IsOverOnePageScrollAllowedX(mozilla::widget::WheelEvent* aEvent);
    bool IsOverOnePageScrollAllowedY(mozilla::widget::WheelEvent* aEvent);

  private:
    WheelPrefs();
    ~WheelPrefs();

    static int OnPrefChanged(const char* aPrefName, void* aClosure);

    enum Index
    {
      INDEX_DEFAULT = 0,
      INDEX_ALT,
      INDEX_CONTROL,
      INDEX_META,
      INDEX_SHIFT,
      INDEX_OS,
      COUNT_OF_MULTIPLIERS
    };

    /**
     * GetIndexFor() returns the index of the members which should be used for
     * the aEvent.  When only one modifier key of MODIFIER_ALT,
     * MODIFIER_CONTROL, MODIFIER_META, MODIFIER_SHIFT or MODIFIER_OS is
     * pressed, returns the index for the modifier.  Otherwise, this return the
     * default index which is used at either no modifier key is pressed or
     * two or modifier keys are pressed.
     */
    Index GetIndexFor(mozilla::widget::WheelEvent* aEvent);

    /**
     * GetPrefNameBase() returns the base pref name for aEvent.
     * It's decided by GetModifierForPref() which modifier should be used for
     * the aEvent.
     *
     * @param aBasePrefName The result, must be "mousewheel.with_*." or
     *                      "mousewheel.default.".
     */
    void GetBasePrefName(Index aIndex, nsACString& aBasePrefName);

    void Init(Index aIndex);

    void Reset();

    /**
     * If the abosolute values of mMultiplierX and/or mMultiplierY are equals or
     * larger than this value, the computed scroll amount isn't rounded down to
     * the page width or height.
     */
    enum {
      MIN_MULTIPLIER_VALUE_ALLOWING_OVER_ONE_PAGE_SCROLL = 1000
    };

    bool mInit[COUNT_OF_MULTIPLIERS];
    double mMultiplierX[COUNT_OF_MULTIPLIERS];
    double mMultiplierY[COUNT_OF_MULTIPLIERS];
    double mMultiplierZ[COUNT_OF_MULTIPLIERS];
    Action mActions[COUNT_OF_MULTIPLIERS];
    /**
     * action values overridden by .override_x pref.
     * If an .override_x value is -1, same as the
     * corresponding mActions value.
     */
    Action mOverriddenActionsX[COUNT_OF_MULTIPLIERS];

    static WheelPrefs* sInstance;
  };

  /**
   * DeltaDirection is used for specifying whether the called method should
   * handle vertical delta or horizontal delta.
   * This is clearer than using bool.
   */
  enum DeltaDirection
  {
    DELTA_DIRECTION_X = 0,
    DELTA_DIRECTION_Y
  };

  /**
   * SendLineScrollEvent() dispatches a DOMMouseScroll event for the
   * widget::WheelEvent.  This method shouldn't be called for non-trusted
   * wheel event because it's not necessary for compatiblity.
   *
   * @param aTargetFrame        The event target of wheel event.
   * @param aEvent              The original Wheel event.
   * @param aStatus             The event status, must not be
   *                            nsEventStatus_eConsumeNoDefault.
   * @param aDelta              The delta value of the event.
   * @param aDeltaDirection     The X/Y direction of dispatching event.
   */
  void SendLineScrollEvent(nsIFrame* aTargetFrame,
                           mozilla::widget::WheelEvent* aEvent,
                           nsEventStatus* aStatus,
                           int32_t aDelta,
                           DeltaDirection aDeltaDirection);

  /**
   * SendPixelScrollEvent() dispatches a MozMousePixelScroll event for the
   * widget::WheelEvent.  This method shouldn't be called for non-trusted
   * wheel event because it's not necessary for compatiblity.
   *
   * @param aTargetFrame        The event target of wheel event.
   * @param aEvent              The original Wheel event.
   * @param aStatus             The event status, must not be
   *                            nsEventStatus_eConsumeNoDefault.
   * @param aPixelDelta         The delta value of the event.
   * @param aDeltaDirection     The X/Y direction of dispatching event.
   */
  void SendPixelScrollEvent(nsIFrame* aTargetFrame,
                            mozilla::widget::WheelEvent* aEvent,
                            nsEventStatus* aStatus,
                            int32_t aPixelDelta,
                            DeltaDirection aDeltaDirection);

  /**
   * ComputeScrollTarget() returns the scrollable frame which should be
   * scrolled.
   *
   * @param aTargetFrame        The event target of the wheel event.
   * @param aEvent              The handling mouse wheel event.
   * @param aOptions            The options for finding the scroll target.
   *                            Callers should use COMPUTE_*.
   * @return                    The scrollable frame which should be scrolled.
   */
  // These flags are used in ComputeScrollTarget(). Callers should use
  // COMPUTE_*.
  enum
  {
    PREFER_MOUSE_WHEEL_TRANSACTION               = 1,
    PREFER_ACTUAL_SCROLLABLE_TARGET_ALONG_X_AXIS = 2,
    PREFER_ACTUAL_SCROLLABLE_TARGET_ALONG_Y_AXIS = 4,
    START_FROM_PARENT                            = 8
  };
  enum ComputeScrollTargetOptions
  {
    // At computing scroll target for legacy mouse events, we should return
    // first scrollable element even when it's not scrollable to the direction.
    COMPUTE_LEGACY_MOUSE_SCROLL_EVENT_TARGET     = 0,
    // Default action prefers the scrolled element immediately before if it's
    // still under the mouse cursor.  Otherwise, it prefers the nearest
    // scrollable ancestor which will be scrolled actually.
    COMPUTE_DEFAULT_ACTION_TARGET                =
      (PREFER_MOUSE_WHEEL_TRANSACTION |
       PREFER_ACTUAL_SCROLLABLE_TARGET_ALONG_X_AXIS |
       PREFER_ACTUAL_SCROLLABLE_TARGET_ALONG_Y_AXIS),
    // Look for the nearest scrollable ancestor which can be scrollable with
    // aEvent.
    COMPUTE_SCROLLABLE_ANCESTOR_ALONG_X_AXIS     =
      (PREFER_ACTUAL_SCROLLABLE_TARGET_ALONG_X_AXIS | START_FROM_PARENT),
    COMPUTE_SCROLLABLE_ANCESTOR_ALONG_Y_AXIS     =
      (PREFER_ACTUAL_SCROLLABLE_TARGET_ALONG_Y_AXIS | START_FROM_PARENT)
  };
  nsIScrollableFrame* ComputeScrollTarget(nsIFrame* aTargetFrame,
                                          mozilla::widget::WheelEvent* aEvent,
                                          ComputeScrollTargetOptions aOptions);

  /**
   * GetScrollAmount() returns the scroll amount in app uints of one line or
   * one page.  If the wheel event scrolls a page, returns the page width and
   * height.  Otherwise, returns line height for both its width and height.
   *
   * @param aScrollableFrame    A frame which will be scrolled by the event.
   *                            The result of ComputeScrollTarget() is
   *                            expected for this value.
   *                            This can be nullptr if there is no scrollable
   *                            frame.  Then, this method uses root frame's
   *                            line height or visible area's width and height.
   */
  nsSize GetScrollAmount(nsPresContext* aPresContext,
                         mozilla::widget::WheelEvent* aEvent,
                         nsIScrollableFrame* aScrollableFrame);

  /**
   * DoScrollText() scrolls the scrollable frame for aEvent.
   */
  void DoScrollText(nsIScrollableFrame* aScrollableFrame,
                    mozilla::widget::WheelEvent* aEvent);

  void DoScrollHistory(int32_t direction);
  void DoScrollZoom(nsIFrame *aTargetFrame, int32_t adjustment);
  nsresult GetMarkupDocumentViewer(nsIMarkupDocumentViewer** aMv);
  nsresult ChangeTextSize(int32_t change);
  nsresult ChangeFullZoom(int32_t change);

  /**
   * DeltaAccumulator class manages delta values for dispatching DOMMouseScroll
   * event.  If wheel events are caused by pixel scroll only devices or
   * the delta values are customized by prefs, this class stores the delta
   * values and set lineOrPageDelta values.
   */
  class DeltaAccumulator
  {
  public:
    static DeltaAccumulator* GetInstance()
    {
      if (!sInstance) {
        sInstance = new DeltaAccumulator;
      }
      return sInstance;
    }

    static void Shutdown()
    {
      delete sInstance;
      sInstance = nullptr;
    }

    bool IsInTransaction() { return mHandlingDeltaMode != UINT32_MAX; }

    /**
     * InitLineOrPageDelta() stores pixel delta values of WheelEvents which are
     * caused if it's needed.  And if the accumulated delta becomes a
     * line height, sets lineOrPageDeltaX and lineOrPageDeltaY automatically.
     */
    void InitLineOrPageDelta(nsIFrame* aTargetFrame,
                             nsEventStateManager* aESM,
                             mozilla::widget::WheelEvent* aEvent);

    /**
     * Reset() resets all members.
     */
    void Reset();

    /**
     * ComputeScrollAmountForDefaultAction() computes the default action's
     * scroll amount in device pixels with mPendingScrollAmount*.
     */
    nsIntPoint ComputeScrollAmountForDefaultAction(
                 mozilla::widget::WheelEvent* aEvent,
                 const nsIntSize& aScrollAmountInDevPixels);

  private:
    DeltaAccumulator() :
      mX(0.0), mY(0.0), mPendingScrollAmountX(0.0), mPendingScrollAmountY(0.0),
      mHandlingDeltaMode(UINT32_MAX), mHandlingPixelOnlyDevice(false)
    {
    }

    double mX;
    double mY;

    // When default action of a wheel event is scroll but some delta values
    // are ignored because the computed amount values are not integer, the
    // fractional values are saved by these members.
    double mPendingScrollAmountX;
    double mPendingScrollAmountY;

    TimeStamp mLastTime;

    uint32_t mHandlingDeltaMode;
    bool mHandlingPixelOnlyDevice;

    static DeltaAccumulator* sInstance;
  };

  // end mousewheel functions

  /*
   * When a touch gesture is about to start, this function determines what
   * kind of gesture interaction we will want to use, based on what is
   * underneath the initial touch point.
   * Currently it decides between panning (finger scrolling) or dragging
   * the target element, as well as the orientation to trigger panning and
   * display visual boundary feedback. The decision is stored back in aEvent.
   */
  void DecideGestureEvent(nsGestureNotifyEvent* aEvent, nsIFrame* targetFrame);

  // routines for the d&d gesture tracking state machine
  void BeginTrackingDragGesture ( nsPresContext* aPresContext, nsMouseEvent* inDownEvent,
                                  nsIFrame* inDownFrame ) ;
  void StopTrackingDragGesture ( ) ;
  void GenerateDragGesture ( nsPresContext* aPresContext, nsMouseEvent *aEvent ) ;

  /**
   * Determine which node the drag should be targeted at.
   * This is either the node clicked when there is a selection, or, for HTML,
   * the element with a draggable property set to true.
   *
   * aSelectionTarget - target to check for selection
   * aDataTransfer - data transfer object that will contain the data to drag
   * aSelection - [out] set to the selection to be dragged
   * aTargetNode - [out] the draggable node, or null if there isn't one
   */
  void DetermineDragTarget(nsPresContext* aPresContext,
                           nsIContent* aSelectionTarget,
                           nsDOMDataTransfer* aDataTransfer,
                           nsISelection** aSelection,
                           nsIContent** aTargetNode);

  /*
   * Perform the default handling for the dragstart/draggesture event and set up a
   * drag for aDataTransfer if it contains any data. Returns true if a drag has
   * started.
   *
   * aDragEvent - the dragstart/draggesture event
   * aDataTransfer - the data transfer that holds the data to be dragged
   * aDragTarget - the target of the drag
   * aSelection - the selection to be dragged
   */
  bool DoDefaultDragStart(nsPresContext* aPresContext,
                            nsDragEvent* aDragEvent,
                            nsDOMDataTransfer* aDataTransfer,
                            nsIContent* aDragTarget,
                            nsISelection* aSelection);

  bool IsTrackingDragGesture ( ) const { return mGestureDownContent != nullptr; }
  /**
   * Set the fields of aEvent to reflect the mouse position and modifier keys
   * that were set when the user first pressed the mouse button (stored by
   * BeginTrackingDragGesture). aEvent->widget must be
   * mCurrentTarget->GetNearestWidget().
   */
  void FillInEventFromGestureDown(nsMouseEvent* aEvent);

  nsresult DoContentCommandEvent(nsContentCommandEvent* aEvent);
  nsresult DoContentCommandScrollEvent(nsContentCommandEvent* aEvent);

  void DoQuerySelectedText(nsQueryContentEvent* aEvent);

  bool RemoteQueryContentEvent(nsEvent *aEvent);
  mozilla::dom::TabParent *GetCrossProcessTarget();
  bool IsTargetCrossProcess(nsGUIEvent *aEvent);

  bool DispatchCrossProcessEvent(nsEvent* aEvent, nsFrameLoader* remote,
                                 nsEventStatus *aStatus);
  bool HandleCrossProcessEvent(nsEvent *aEvent,
                                 nsIFrame* aTargetFrame,
                                 nsEventStatus *aStatus);

private:
  static inline void DoStateChange(mozilla::dom::Element* aElement,
                                   nsEventStates aState, bool aAddState);
  static inline void DoStateChange(nsIContent* aContent, nsEventStates aState,
                                   bool aAddState);
  static void UpdateAncestorState(nsIContent* aStartNode,
                                  nsIContent* aStopBefore,
                                  nsEventStates aState,
                                  bool aAddState);

  int32_t     mLockCursor;

  // Last mouse event refPoint (the offset from the widget's origin in
  // device pixels) when mouse was locked, used to restore mouse position
  // after unlocking.
  nsIntPoint  mPreLockPoint;

  // Stores the refPoint of the last synthetic mouse move we dispatched
  // to re-center the mouse when we were pointer locked. If this is (-1,-1) it
  // means we've not recently dispatched a centering event. We use this to
  // detect when we receive the synth event, so we can cancel and not send it
  // to content.
  static nsIntPoint sSynthCenteringPoint;

  nsWeakFrame mCurrentTarget;
  nsCOMPtr<nsIContent> mCurrentTargetContent;
  nsWeakFrame mLastMouseOverFrame;
  nsCOMPtr<nsIContent> mLastMouseOverElement;
  static nsWeakFrame sLastDragOverFrame;

  // Stores the refPoint (the offset from the widget's origin in device
  // pixels) of the last mouse event.
  static nsIntPoint sLastRefPoint;

  // member variables for the d&d gesture state machine
  nsIntPoint mGestureDownPoint; // screen coordinates
  // The content to use as target if we start a d&d (what we drag).
  nsCOMPtr<nsIContent> mGestureDownContent;
  // The content of the frame where the mouse-down event occurred. It's the same
  // as the target in most cases but not always - for example when dragging
  // an <area> of an image map this is the image. (bug 289667)
  nsCOMPtr<nsIContent> mGestureDownFrameOwner;
  // State of keys when the original gesture-down happened
  mozilla::widget::Modifiers mGestureModifiers;
  uint16_t mGestureDownButtons;

  nsCOMPtr<nsIContent> mLastLeftMouseDownContent;
  nsCOMPtr<nsIContent> mLastLeftMouseDownContentParent;
  nsCOMPtr<nsIContent> mLastMiddleMouseDownContent;
  nsCOMPtr<nsIContent> mLastMiddleMouseDownContentParent;
  nsCOMPtr<nsIContent> mLastRightMouseDownContent;
  nsCOMPtr<nsIContent> mLastRightMouseDownContentParent;

  nsCOMPtr<nsIContent> mActiveContent;
  nsCOMPtr<nsIContent> mHoverContent;
  static nsCOMPtr<nsIContent> sDragOverContent;
  nsCOMPtr<nsIContent> mURLTargetContent;

  // The last element on which we fired a mouseover event, or null if
  // the last mouseover event we fired has finished processing.
  nsCOMPtr<nsIContent> mFirstMouseOverEventElement;

  // The last element on which we fired a mouseout event, or null if
  // the last mouseout event we fired has finished processing.
  nsCOMPtr<nsIContent> mFirstMouseOutEventElement;

  nsPresContext* mPresContext;      // Not refcnted
  nsCOMPtr<nsIDocument> mDocument;   // Doesn't necessarily need to be owner

  uint32_t mLClickCount;
  uint32_t mMClickCount;
  uint32_t mRClickCount;

  bool m_haveShutdown;

  // Time at which we began handling user input.
  static TimeStamp sHandlingInputStart;

public:
  static nsresult UpdateUserActivityTimer(void);
  // Array for accesskey support
  nsCOMArray<nsIContent> mAccessKeys;

  static int32_t sUserInputEventDepth;
  
  static bool sNormalLMouseEventInProcess;

  static nsEventStateManager* sActiveESM;
  
  static void ClearGlobalActiveContent(nsEventStateManager* aClearer);

  // Functions used for click hold context menus
  bool mClickHoldContextMenu;
  nsCOMPtr<nsITimer> mClickHoldTimer;
  void CreateClickHoldTimer ( nsPresContext* aPresContext, nsIFrame* inDownFrame,
                              nsGUIEvent* inMouseDownEvent ) ;
  void KillClickHoldTimer ( ) ;
  void FireContextClick ( ) ;

  void SetPointerLock(nsIWidget* aWidget, nsIContent* aElement) ;
  static void sClickHoldCallback ( nsITimer* aTimer, void* aESM ) ;
};

/**
 * This class is used while processing real user input. During this time, popups
 * are allowed. For mousedown events, mouse capturing is also permitted.
 */
class nsAutoHandlingUserInputStatePusher
{
public:
  nsAutoHandlingUserInputStatePusher(bool aIsHandlingUserInput,
                                     nsEvent* aEvent,
                                     nsIDocument* aDocument)
    : mIsHandlingUserInput(aIsHandlingUserInput),
      mIsMouseDown(aEvent && aEvent->message == NS_MOUSE_BUTTON_DOWN),
      mResetFMMouseDownState(false)
  {
    if (aIsHandlingUserInput) {
      nsEventStateManager::StartHandlingUserInput();
      if (mIsMouseDown) {
        nsIPresShell::SetCapturingContent(nullptr, 0);
        nsIPresShell::AllowMouseCapture(true);
        if (aDocument && aEvent->mFlags.mIsTrusted) {
          nsFocusManager* fm = nsFocusManager::GetFocusManager();
          if (fm) {
            fm->SetMouseButtonDownHandlingDocument(aDocument);
            mResetFMMouseDownState = true;
          }
        }
      }
    }
  }

  ~nsAutoHandlingUserInputStatePusher()
  {
    if (mIsHandlingUserInput) {
      nsEventStateManager::StopHandlingUserInput();
      if (mIsMouseDown) {
        nsIPresShell::AllowMouseCapture(false);
        if (mResetFMMouseDownState) {
          nsFocusManager* fm = nsFocusManager::GetFocusManager();
          if (fm) {
            fm->SetMouseButtonDownHandlingDocument(nullptr);
          }
        }
      }
    }
  }

protected:
  bool mIsHandlingUserInput;
  bool mIsMouseDown;
  bool mResetFMMouseDownState;

private:
  // Hide so that this class can only be stack-allocated
  static void* operator new(size_t /*size*/) CPP_THROW_NEW { return nullptr; }
  static void operator delete(void* /*memory*/) {}
};

// Click and double-click events need to be handled even for content that
// has no frame. This is required for Web compatibility.
#define NS_EVENT_NEEDS_FRAME(event) \
    (!NS_IS_ACTIVATION_EVENT(event) && (event)->message != NS_MOUSE_CLICK && \
     (event)->message != NS_MOUSE_DOUBLECLICK)

#endif // nsEventStateManager_h__
