--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/uifw/ganes/src/HgVgSpring.cpp	Tue Feb 02 01:00:49 2010 +0200
@@ -0,0 +1,195 @@
+/*
+* Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
+* All rights reserved.
+* This component and the accompanying materials are made available
+* under the terms of "Eclipse Public License v1.0"
+* which accompanies this distribution, and is available
+* at the URL "http://www.eclipse.org/legal/epl-v10.html".
+*
+* Initial Contributors:
+* Nokia Corporation - initial contribution.
+*
+* Contributors:
+*
+* Description:    
+*
+*/
+
+// INCLUDE FILES
+
+#include "HgVgSpring.h"
+#include "HgVgConstants.h"
+
+#include <e32math.h>
+
+using namespace HgVgConstants;
+
+
+THgVgSpring::THgVgSpring(TReal aSpringK, TReal aSpringDamping, 
+                TReal aSpringMaxVelocity, TReal aPositionSnap,
+                TReal aVelocitySnap) : 
+iPrevX(0), 
+iPrevY(0),
+iX(0), 
+iY(0),
+iEndX(0), 
+iEndY(0),
+iVelX(0), 
+iVelY(0),
+iAccumulator(0),
+iSpringK(aSpringK),
+iSpringDamping(aSpringDamping),
+iMaxSpringVelocity(aSpringMaxVelocity),
+iPositionSnap(aPositionSnap),
+iVelocitySnap(aVelocitySnap),
+iStartX(0),
+iStartY(0)
+    {
+    
+    }
+
+void THgVgSpring::SetConstants(TReal aSpringK, TReal aSpringDamping, 
+    TReal aSpringMaxVelocity, TReal aPositionSnap,
+    TReal aVelocitySnap)
+    {
+    iSpringK = aSpringK;
+    iSpringDamping = aSpringDamping;
+    iMaxSpringVelocity = aSpringMaxVelocity;
+    iPositionSnap = aPositionSnap;
+    iVelocitySnap = aVelocitySnap;
+    }
+
+
+void THgVgSpring::Reset(TReal aX, TReal aY)
+    {
+    iEndX = aX;
+    iEndY = aY;
+    Reset();
+    }
+
+void THgVgSpring::Reset()
+    {
+    iPrevX = iX = iStartX = iEndX;
+    iPrevY = iY = iStartY = iEndY;
+    iAccumulator = 0;
+    iVelX = 0;
+    iVelY = 0;
+    }
+
+void THgVgSpring::SetXY(TReal aX, TReal aY)
+    {
+    iStartX = iPrevX = iX = aX;
+    iStartY = iPrevY = iY = aY;
+    }
+
+void THgVgSpring::SetEnd(TReal aX, TReal aY)
+    {
+    iStartX = iEndX;
+    iStartY = iEndY;
+    iEndX = aX;
+    iEndY = aY;
+    }
+
+void THgVgSpring::SetVelocity(TReal aVx, TReal aVy)
+    {
+    iVelX = aVx;
+    iVelY = aVy;
+    }
+
+TBool THgVgSpring::IntegratePhysics(TReal aDeltaTime, TBool aEndCondition)
+    {
+    iAccumulator += aDeltaTime;    
+    while (iAccumulator >= KTimeStep)
+        {
+        iPrevX = iX;
+        iPrevY = iY;
+
+        // calculate spring force F = -kx - bv
+        TReal Fx = -(iX - iEndX) * iSpringK - iVelX * iSpringDamping;
+        TReal Fy = -(iY - iEndY) * iSpringK - iVelY * iSpringDamping;
+        
+        // do euler integration
+        iVelX += Fx * KTimeStep;
+        iVelY += Fy * KTimeStep;
+                
+        // limit velocity to certain max
+        if (Abs(iVelX) > iMaxSpringVelocity)
+            iVelX = (iVelX < 0) ? -iMaxSpringVelocity : iMaxSpringVelocity;
+        
+        if (Abs(iVelY) > iMaxSpringVelocity)
+            iVelY = (iVelY < 0) ? -iMaxSpringVelocity : iMaxSpringVelocity;
+
+        // do euler integration
+        iX += iVelX * KTimeStep;
+        iY += iVelY * KTimeStep;
+        
+        // decrease accumulator
+        iAccumulator -= KTimeStep;
+
+        // snap to item if close enough and speed is small enough
+        if (Abs(iX - iEndX) < iPositionSnap && Abs(iVelX) < iVelocitySnap &&
+                Abs(iY - iEndY) < iPositionSnap && Abs(iVelY) < iVelocitySnap && aEndCondition)
+            {
+            Reset();
+            return ETrue;
+            }
+                
+        }
+    
+    return EFalse;
+    }
+
+TReal THgVgSpring::GetX() const
+    {
+    return iX;
+    }
+
+TReal THgVgSpring::GetY() const
+    {
+    return iY;
+    }
+
+TReal THgVgSpring::EndX() const
+    {
+    return iEndX;
+    }
+
+TReal THgVgSpring::EndY() const
+    {
+    return iEndY;
+    }
+
+TReal THgVgSpring::VelX() const
+    {
+    return iVelX;
+    }
+
+TReal THgVgSpring::VelY() const
+    {
+    return iVelY;
+    }
+
+TReal THgVgSpring::GetInterpolatedX() const
+    {
+    TReal a = iAccumulator / KTimeStep;
+    return iX * (1.0 - a) + iPrevX * a;    
+    }
+
+TReal THgVgSpring::GetInterpolatedY() const
+    {
+    TReal a = iAccumulator / KTimeStep;
+    return iY * (1.0 - a) + iPrevY * a;
+    }
+
+TReal THgVgSpring::StartX() const
+    {
+    return iStartX;
+    }
+
+TReal THgVgSpring::StartY() const
+    {
+    return iStartY;
+    }
+
+
+// End of File