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Torque/SDK/engine/core/iTickable.h

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+//-----------------------------------------------------------------------------
+// Torque Game Engine
+// Copyright (C) GarageGames.com, Inc.
+//-----------------------------------------------------------------------------
+
+#ifndef _ITICKABLE_H_
+#define _ITICKABLE_H_
+
+#include "core/tVector.h"
+
+/// This interface allows you to let any object be ticked. You use it like so:
+/// @code
+/// class FooClass : public SimObject, public virtual ITickable
+/// {
+///    // You still mark SimObject as Parent
+///    typdef SimObject Parent;
+/// private:
+/// ...
+///
+/// protected:
+///    // These three methods are the interface for ITickable
+///    virtual void interpolateTick( F32 delta );
+///    virtual void processTick();
+///    virtual void advanceTime( F32 timeDelta );
+///
+/// public:
+/// ...
+/// };
+/// @endcode
+/// Please note the three methods you must implement to use ITickable, but don't
+/// worry. If you forget, the compiler will tell you so. Also note that the
+/// typedef for Parent should NOT BE SET to ITickable, the compiler will <i>probably</i>
+/// also tell you if you forget that. Last, but assuridly not least is that you note
+/// the way that the inheretance is done: public <b>virtual</b> ITickable
+/// It is very important that you keep the virtual keyword in there, otherwise
+/// proper behavior is not guarenteed. You have been warned.
+///
+/// The point of a tickable object is that the object gets ticks at a fixed rate
+/// which is one tick every 32ms. This means, also, that if an object doesn't get
+/// updated for 64ms, that the next update it will get two-ticks. Basically it
+/// comes down to this. You are assured to get one tick per 32ms of time passing
+/// provided that isProcessingTicks returns true when ITickable calls it.
+///
+/// isProcessingTicks is a virtual method and you can (should you want to)
+/// override it and put some extended functionality to decide if you want to
+/// recieve tick-notification or not.
+///
+/// The other half of this is that you get time-notification from advanceTime.
+/// advanceTime lets you know when time passes regardless of the return value
+/// of isProcessingTicks. The object WILL get the advanceTime call every single
+/// update. The argument passed to advanceTime is the time since the last call
+/// to advanceTime. Updates are not based on the 32ms tick time. Updates are
+/// dependant on framerate. So you may get 200 advanceTime calls in a second, or you
+/// may only get 20. There is no way of assuring consistant calls of advanceTime
+/// like there is with processTick. Both are useful for different things, and
+/// it is important to understand the differences between them.
+///
+/// Interpolation is the last part of the ITickable interface. It is called
+/// every update, as long as isProcessingTicks evaluates to true on the object.
+/// This is used to interpolate between 32ms ticks. The argument passed to
+/// interpolateTick is the time since the last call to processTick. You can see
+/// in the code for ITickable::advanceTime that before a tick occurs it calls
+/// interpolateTick(0) on every object. This is to tell objects which do interpolate
+/// between ticks to reset their interpolation because they are about to get a
+/// new tick.
+///
+/// This is an extremely powerful interface when used properly. An example of a class
+/// that properly uses this interface is GuiTickCtrl. The documentation for that
+/// class describes why it was created and why it was important that it use
+/// a consistant update frequency for its effects.
+/// @see GuiTickCtrl
+///
+/// @todo Support processBefore/After and move the GameBase processing over to use ITickable
+class ITickable
+{
+private:
+   static U32 smLastTick;  ///< Time of the last tick that occurred
+   static U32 smLastTime;  ///< Last time value at which advanceTime was called
+   static U32 smLastDelta; ///< Last delta value for advanceTime
+
+   // This just makes life easy
+   typedef Vector<ITickable *>::iterator ProcessListIterator;
+   static Vector<ITickable *> smProcessList; ///< List of tick controls
+
+protected:
+   bool mProcessTick; ///< Set to true if this object wants tick processing
+
+   /// This method is called every frame and lets the control interpolate between
+   /// ticks so you can smooth things as long as isProcessingTicks returns true
+   /// when it is called on the object
+   virtual void interpolateTick( F32 delta ) = 0;
+
+   /// This method is called once every 32ms if isProcessingTicks returns true
+   /// when called on the object
+   virtual void processTick() = 0;
+
+   /// This method is called once every frame regardless of the return value of
+   /// isProcessingTicks and informs the object of the passage of time
+   virtual void advanceTime( F32 timeDelta ) = 0;
+
+public:
+   // Can let everyone look at these if they want to
+   static const U32 smTickShift;    ///< Shift value to control how often Ticks occur
+   static const U32 smTickMs;       ///< Number of milliseconds per tick, 32 in this case
+   static const F32 smTickSec;      ///< Fraction of a second per tick
+   static const U32 smTickMask;
+
+   /// Constructor
+   /// This will add the object to the process list
+   ITickable();
+
+   /// Destructor
+   /// Remove this object from the process list
+   virtual ~ITickable();
+
+   /// Is this object wanting to receive tick notifications
+   /// @returns True if object wants tick notifications
+   virtual bool isProcessingTicks() const { return mProcessTick; };
+
+   /// Sets this object as either tick processing or not
+   /// @parm   tick     True if this object should process ticks
+   virtual void setProcessTicks( bool tick = true );
+
+//------------------------------------------------------------------------------
+
+   /// This is called in clientProcess to advance the time for all ITickable
+   /// objects
+   /// @returns True if any ticks were sent
+   /// @see clientProcess
+   static bool advanceTime( U32 timeDelta );
+};
+
+//------------------------------------------------------------------------------
+
+inline void ITickable::setProcessTicks( bool tick /* = true  */ )
+{
+   mProcessTick = tick;
+}
+
+#endif