dom/smil/nsSMILMilestone.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef NS_SMILMILESTONE_H_
   7 #define NS_SMILMILESTONE_H_
   8
   9 /*
  10  * A significant moment in an nsSMILTimedElement's lifetime where a sample is
  11  * required.
  12  *
  13  * Animations register the next milestone in their lifetime with the time
  14  * container that they belong to. When the animation controller goes to run
  15  * a sample it first visits all the animations that have a registered milestone
  16  * in order of their milestone times. This allows interdependencies between
  17  * animations to be correctly resolved and events to fire in the proper order.
  18  *
  19  * A distinction is made between a milestone representing the end of an interval
  20  * and any other milestone. This is because if animation A ends at time t, and
  21  * animation B begins at the same time t (or has some other significant moment
  22  * such as firing a repeat event), SMIL's endpoint-exclusive timing model
  23  * implies that the interval end occurs first. In fact, interval ends can be
  24  * thought of as ending an infinitesimally small time before t. Therefore,
  25  * A should be sampled before B.
  26  *
  27  * Furthermore, this distinction between sampling the end of an interval and
  28  * a regular sample is used within the timing model (specifically in
  29  * nsSMILTimedElement) to ensure that all intervals ending at time t are sampled
  30  * before any new intervals are entered so that we have a fully up-to-date set
  31  * of instance times available before committing to a new interval. Once an
  32  * interval is entered, the begin time is fixed.
  33  */
  34 class nsSMILMilestone
  35 {
  36 public:
  37   nsSMILMilestone(nsSMILTime aTime, bool aIsEnd)
  38     : mTime(aTime), mIsEnd(aIsEnd)
  39   { }
  40
  41   nsSMILMilestone()
  42     : mTime(0), mIsEnd(false)
  43   { }
  44
  45   bool operator==(const nsSMILMilestone& aOther) const
  46   {
  47     return mTime == aOther.mTime && mIsEnd == aOther.mIsEnd;
  48   }
  49
  50   bool operator!=(const nsSMILMilestone& aOther) const
  51   {
  52     return !(*this == aOther);
  53   }
  54
  55   bool operator<(const nsSMILMilestone& aOther) const
  56   {
  57     // Earlier times sort first, and for equal times end milestones sort first
  58     return mTime < aOther.mTime ||
  59           (mTime == aOther.mTime && mIsEnd && !aOther.mIsEnd);
  60   }
  61
  62   bool operator<=(const nsSMILMilestone& aOther) const
  63   {
  64     return *this == aOther || *this < aOther;
  65   }
  66
  67   bool operator>=(const nsSMILMilestone& aOther) const
  68   {
  69     return !(*this < aOther);
  70   }
  71
  72   nsSMILTime   mTime;  // The milestone time. This may be in container time or
  73                        // parent container time depending on where it is used.
  74   bool mIsEnd; // true if this milestone corresponds to an interval
  75                        // end, false otherwise.
  76 };
  77
  78 #endif // NS_SMILMILESTONE_H_