dom/smil/SMILMilestone.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef DOM_SMIL_SMILMILESTONE_H_
   8 #define DOM_SMIL_SMILMILESTONE_H_
   9
  10 #include "mozilla/SMILTypes.h"
  11
  12 namespace mozilla {
  13
  14 /*
  15  * A significant moment in an SMILTimedElement's lifetime where a sample is
  16  * required.
  17  *
  18  * Animations register the next milestone in their lifetime with the time
  19  * container that they belong to. When the animation controller goes to run
  20  * a sample it first visits all the animations that have a registered milestone
  21  * in order of their milestone times. This allows interdependencies between
  22  * animations to be correctly resolved and events to fire in the proper order.
  23  *
  24  * A distinction is made between a milestone representing the end of an interval
  25  * and any other milestone. This is because if animation A ends at time t, and
  26  * animation B begins at the same time t (or has some other significant moment
  27  * such as firing a repeat event), SMIL's endpoint-exclusive timing model
  28  * implies that the interval end occurs first. In fact, interval ends can be
  29  * thought of as ending an infinitesimally small time before t. Therefore,
  30  * A should be sampled before B.
  31  *
  32  * Furthermore, this distinction between sampling the end of an interval and
  33  * a regular sample is used within the timing model (specifically in
  34  * SMILTimedElement) to ensure that all intervals ending at time t are sampled
  35  * before any new intervals are entered so that we have a fully up-to-date set
  36  * of instance times available before committing to a new interval. Once an
  37  * interval is entered, the begin time is fixed.
  38  */
  39 class SMILMilestone {
  40  public:
  41   SMILMilestone(SMILTime aTime, bool aIsEnd) : mTime(aTime), mIsEnd(aIsEnd) {}
  42
  43   SMILMilestone() : mTime(0), mIsEnd(false) {}
  44
  45   bool operator==(const SMILMilestone& aOther) const {
  46     return mTime == aOther.mTime && mIsEnd == aOther.mIsEnd;
  47   }
  48
  49   bool operator!=(const SMILMilestone& aOther) const {
  50     return !(*this == aOther);
  51   }
  52
  53   bool operator<(const SMILMilestone& aOther) const {
  54     // Earlier times sort first, and for equal times end milestones sort first
  55     return mTime < aOther.mTime ||
  56            (mTime == aOther.mTime && mIsEnd && !aOther.mIsEnd);
  57   }
  58
  59   bool operator<=(const SMILMilestone& aOther) const {
  60     return *this == aOther || *this < aOther;
  61   }
  62
  63   bool operator>=(const SMILMilestone& aOther) const {
  64     return !(*this < aOther);
  65   }
  66
  67   SMILTime mTime;  // The milestone time. This may be in container time or
  68                    // parent container time depending on where it is used.
  69   bool mIsEnd;     // true if this milestone corresponds to an interval
  70                    // end, false otherwise.
  71 };
  72
  73 }  // namespace mozilla
  74
  75 #endif  // DOM_SMIL_SMILMILESTONE_H_