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SpriteAction_AlphaFade.cpp

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//*** SpriteAction_AlphaFade.cpp ***
 
#include "SpriteAction_AlphaFade.h"
#include "ColorHelper.h"
#include "Sprite.h"
#include "StandardLibrary.h"


//*** Constructor ***

SpriteAction_AlphaFade::SpriteAction_AlphaFade(unsigned char targetAlpha, float time):
   targetAlpha_(targetAlpha),
   time_(time),
   elapsedTime_(0),
   sourceA_(0),
   targetA_(0),
   deltaA_(0)
   {
   if (time_<=0)
      {
      time_=FLOAT_EPSILON;
      }
   }


//*** Setup ***

void SpriteAction_AlphaFade::Setup(SpriteController* controller, Sprite* sprite)
   {
   unsigned char sourceAlpha=sprite->GetAlpha();
   sourceA_=((float)sourceAlpha)/255.0f;

   targetA_=((float)targetAlpha_)/255.0f;

   deltaA_=(targetA_-sourceA_)/time_;
   }


//*** Update ***

void SpriteAction_AlphaFade::Update(SpriteController* controller, Sprite* sprite, float deltaTime)
   {
   elapsedTime_+=deltaTime;
   
   if (elapsedTime_>time_)
      {  
      sprite->SetAlpha(targetAlpha_);
      ActionCompleted();
      return;
      }

   float a=sourceA_+deltaA_*elapsedTime_;
   if (targetA_<sourceA_)
      {
      a=Max(a,targetA_);
      }
   else
      {
      a=Min(a,targetA_);
      }

   unsigned char alpha=(unsigned char)(a*255.0f);
   sprite->SetAlpha(alpha);
   }

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