SMILInstanceTime.h

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

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* 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 DOM_SMIL_SMILINSTANCETIME_H_

#define DOM_SMIL_SMILINSTANCETIME_H_

#include "mozilla/EnumSet.h"

#include "mozilla/SMILTimeValue.h"

#include "nsISupportsImpl.h"

namespace mozilla {

class SMILInterval;

class SMILTimeContainer;

class SMILTimeValueSpec;

//----------------------------------------------------------------------

// SMILInstanceTime

//

// An instant in document simple time that may be used in creating a new

// interval.

//

// For an overview of how this class is related to other SMIL time classes see

// the documentation in SMILTimeValue.h

//

// These objects are owned by an SMILTimedElement but MAY also be referenced

// by:

//

// a) SMILIntervals that belong to the same SMILTimedElement and which refer

//    to the SMILInstanceTimes which form the interval endpoints; and/or

// b) SMILIntervals that belong to other SMILTimedElements but which need to

//    update dependent instance times when they change or are deleted.

//    E.g. for begin='a.begin', 'a' needs to inform dependent

//    SMILInstanceTimes if its begin time changes. This notification is

//    performed by the SMILInterval.

class SMILInstanceTime final {

 public:

  // Instance time source. Times generated by events, syncbase relationships,

  // and DOM calls behave differently in some circumstances such as when a timed

  // element is reset.

  enum class SMILInstanceTimeSource {

    // No particularly significant source, e.g. offset time, 'indefinite'

    None,

    // Generated by a DOM call such as beginElement

    DOM,

    // Generated by a syncbase relationship

    Syncbase,

    // Generated by an event

    Event

};

  explicit SMILInstanceTime(

      const SMILTimeValue& aTime,

      SMILInstanceTimeSource aSource = SMILInstanceTimeSource::None,

      SMILTimeValueSpec* aCreator = nullptr,

      SMILInterval* aBaseInterval = nullptr);

  void Unlink();

  void HandleChangedInterval(const SMILTimeContainer* aSrcContainer,

                             bool aBeginObjectChanged, bool aEndObjectChanged);

  void HandleDeletedInterval();

  void HandleFilteredInterval();

  const SMILTimeValue& Time() const { return mTime; }

  const SMILTimeValueSpec* GetCreator() const { return mCreator; }

  bool IsDynamic() const { return mFlags.contains(Flag::Dynamic); }

  bool IsFixedTime() const { return !mFlags.contains(Flag::MayUpdate); }

  bool FromDOM() const { return mFlags.contains(Flag::FromDOM); }

  bool ShouldPreserve() const;

  void UnmarkShouldPreserve();

  void AddRefFixedEndpoint();

  void ReleaseFixedEndpoint();

  void DependentUpdate(const SMILTimeValue& aNewTime) {

    MOZ_ASSERT(!IsFixedTime(),

               "Updating an instance time that is not expected to be updated");

    mTime = aNewTime;

  bool IsDependent() const { return !!mBaseInterval; }

  bool IsDependentOn(const SMILInstanceTime& aOther) const;

  const SMILInterval* GetBaseInterval() const { return mBaseInterval; }

  const SMILInstanceTime* GetBaseTime() const;

  bool SameTimeAndBase(const SMILInstanceTime& aOther) const {

    return mTime == aOther.mTime && GetBaseTime() == aOther.GetBaseTime();

  // Get and set a serial number which may be used by a containing class to

  // control the sort order of otherwise similar instance times.

  uint32_t Serial() const { return mSerial; }

  void SetSerial(uint32_t aIndex) { mSerial = aIndex; }

  NS_INLINE_DECL_REFCOUNTING(SMILInstanceTime)

 private:

  // Private destructor, to discourage deletion outside of Release():

  ~SMILInstanceTime();

  void SetBaseInterval(SMILInterval* aBaseInterval);

  // The SMILTimeValueSpec object that created us.

  // (currently only needed for syncbase instance times.)

  SMILTimeValueSpec* mCreator;

  // Interval from which this time is derived

  // (only used for syncbase instance times).

  SMILInterval* mBaseInterval = nullptr;

  SMILTimeValue mTime;

  // A serial number used by the containing class to specify the sort order

  // for instance times with the same mTime.

  uint32_t mSerial = 0;

  // Additional reference count to determine if this instance time is currently

  // used as a fixed endpoint in any intervals. Instance times that are used in

  // this way should not be removed when the owning SMILTimedElement removes

  // instance times in response to a restart or in an attempt to free up memory

  // by filtering out old instance times.

//

  // Instance times are only shared in a few cases, namely:

  // a) early ends,

  // b) zero-duration intervals,

  // c) momentarily whilst establishing new intervals and updating the current

  //    interval, and

  // d) trimmed intervals

  // Hence the limited range of a uint16_t should be more than adequate.

  uint16_t mFixedEndpointRefCnt = 0;

  mutable bool mVisited = false;  // Cycle tracking

  // Internal flags used to represent the behaviour of different instance times

  enum class Flag : uint8_t {

    // Indicates that this instance time was generated by an event or a DOM

    // call. Such instance times require special handling when (i) the owning

    // element is reset, (ii) when they are to be added as a new end instance

    // times (as per SMIL's event sensitivity contraints), and (iii) when

    // a backwards seek is performed and the timing model is reconstructed.

    Dynamic,

    // Indicates that this instance time is referred to by an

    // SMILTimeValueSpec and as such may be updated. Such instance time should

    // not be filtered out by the SMILTimedElement even if they appear to be

    // in the past as they may be updated to a future time.

    MayUpdate,

    // Indicates that this instance time was generated from the DOM as opposed

    // to an SMILTimeValueSpec. When a 'begin' or 'end' attribute is set or

    // reset we should clear all the instance times that have been generated by

    // that attribute (and hence an SMILTimeValueSpec), but not those from the

    // DOM.

    FromDOM,

    // Indicates that this instance time was used as the endpoint of an interval

    // that has been filtered or removed. However, since it is a dynamic time it

    // should be preserved and not filtered.

    WasDynamicEndpoint

};

  using Flags = EnumSet<Flag>;

  Flags mFlags;

};

}  // namespace mozilla

#endif  // DOM_SMIL_SMILINSTANCETIME_H_