slideshow/source/inc/eventqueue.hxx

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  19
  20 #ifndef INCLUDED_SLIDESHOW_SOURCE_INC_EVENTQUEUE_HXX
  21 #define INCLUDED_SLIDESHOW_SOURCE_INC_EVENTQUEUE_HXX
  22
  23 #include <canvas/elapsedtime.hxx>
  24
  25 #include "event.hxx"
  26
  27 #include <mutex>
  28 #include <queue>
  29 #include <utility>
  30 #include <vector>
  31
  32
  33 /* Definition of ActivitiesQueue class */
  34
  35 namespace slideshow::internal
  36     {
  37         /** This class handles events in a presentation. Events are
  38             time instants where e.g. effects start.
  39          */
  40         class EventQueue
  41         {
  42         public:
  43             EventQueue(
  44                 std::shared_ptr< ::canvas::tools::ElapsedTime > pPresTimer );
  45
  46             ~EventQueue();
  47
  48             EventQueue(const EventQueue&) = delete;
  49             EventQueue& operator=(const EventQueue&) = delete;
  50
  51             /** Add the given event to the queue. The event is fired
  52                 at, or shortly after, its Event::getActivationTime instant.
  53              */
  54             bool addEvent( const EventSharedPtr& event );
  55
  56             /** Add the given event to the queue. The event is fired
  57                 at, or shortly after, its Event::getActivationTime instant.
  58                 The difference to addEvent() is that events added during
  59                 process() are postponed to next process().
  60              */
  61             bool addEventForNextRound( const EventSharedPtr& event );
  62
  63             /** Another way to control the order of asynchronous event
  64                 execution.  Use this method to schedule events that are to
  65                 be executed after all regular events that have no delay,
  66                 even when they schedule new regular events without delay.
  67             */
  68             bool addEventWhenQueueIsEmpty (const EventSharedPtr& rpEvent);
  69
  70             /** Process the event queue.
  71
  72                 This method executes all events whose timeout has
  73                 expired when calling this method (i.e. all events
  74                 whose scheduled time is less or equal the current
  75                 time).
  76
  77                 Check for the next available event's timeout via
  78                 nextTimeout(), or whether the queue is empty
  79                 altogether via isEmpty().
  80              */
  81             void process();
  82
  83             /** Query state of the queue
  84
  85                 @return false, if queue is empty, true otherwise
  86              */
  87             bool isEmpty() const;
  88
  89             /** Query timeout for the topmost event in the queue.
  90
  91                 @return Timeout in seconds, until the next event is
  92                 ready. The time returned here is relative to the pres
  93                 timer (i.e. the timer specified at the EventQueue
  94                 constructor). When the queue is empty (i.e. isEmpty()
  95                 returns true), the returned value is the highest
  96                 representable double value
  97                 (::std::numeric_limits<double>::max()). If the topmost
  98                 event in the queue is already pending, the timeout
  99                 returned here will actually be negative.
 100             */
 101             double nextTimeout() const;
 102
 103             /** Remove all pending events from the queue.
 104              */
 105             void clear();
 106
 107             /** Forces an empty queue, firing all events immediately
 108                 without minding any times.
 109                 @attention do only call from event loop, this calls process_()!
 110              */
 111             void forceEmpty();
 112
 113             /** Gets the queue's timer object.
 114              */
 115             std::shared_ptr< ::canvas::tools::ElapsedTime > const &
 116             getTimer() const { return mpTimer; }
 117
 118         private:
 119             mutable std::mutex      maMutex;
 120
 121             struct EventEntry
 122             {
 123                 EventSharedPtr  pEvent;
 124                 double          nTime;
 125
 126                 bool operator<( const EventEntry& ) const; // to leverage priority_queue's default compare
 127
 128                 EventEntry( EventSharedPtr p, double t )
 129                     : pEvent(std::move(p)), nTime(t) {}
 130             };
 131
 132             typedef ::std::priority_queue< EventEntry > ImplQueueType;
 133             ImplQueueType                   maEvents;
 134             typedef ::std::vector<EventEntry> EventEntryVector;
 135             EventEntryVector                maNextEvents;
 136             ImplQueueType                   maNextNextEvents;
 137             void process_( bool bFireAllEvents );
 138
 139             // perform timing of events via relative time
 140             // measurements. The world time starts, when the
 141             // EventQueue object is created
 142             std::shared_ptr< ::canvas::tools::ElapsedTime > mpTimer;
 143         };
 144
 145 }
 146 #endif // INCLUDED_SLIDESHOW_SOURCE_INC_EVENTQUEUE_HXX
 147
 148 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */