Add Easing code to make scrolling in grid view more fluid

projects/mtg/include/GridDeckView.h

@@ -3,14 +3,80 @@
 
 #include "DeckView.h"
 
+class Easing
+{
+public:
+    float start_value;
+    float delta_value;
+    float value;
+    float duration;
+    float time_acc;
+
+
+    Easing(float val): start_value(val), delta_value(0), value(val), duration(0), time_acc(0)
+    {}
+
+    void reset(){ value = start_value; time_acc = 0;}
+    void finish(){ value = start_value + delta_value; time_acc = 0; duration = 0;}
+    virtual void update(float dt) = 0;
+
+    void start(float targetValue, float _duration){
+        start_value = value;
+        delta_value = targetValue - start_value;
+        time_acc = 0;
+        duration = _duration;
+    }
+
+    void transpose(float delta_value){
+        start_value += delta_value;
+        value += delta_value;
+    }
+
+    bool finished()
+    {
+        return time_acc >= duration;
+    }
+};
+
+class InOutQuadEasing : public Easing
+{
+public:
+    InOutQuadEasing(float val): Easing(val) {}
+
+    void update(float dt){
+        if(duration > 0){
+            time_acc += dt;
+
+            if(time_acc > duration)
+            {
+                time_acc = duration;
+                value = start_value + delta_value;
+            }
+            else
+            {
+                float time_tmp = time_acc * 2 / duration;
+                if (time_tmp < 1)
+                {
+                    value = delta_value/2*time_tmp*time_tmp + start_value;
+                }
+                else
+                {
+                    time_tmp -= 1;
+                    value = -delta_value/2 * (time_tmp*(time_tmp-2) - 1) + start_value;
+                }
+            }
+        }
+    }
+};
+
 class GridDeckView : public DeckView
 {
 private:
     enum AnimationStage{
         NONE = 0,
         SLIDE_UP,
-        SLIDE_DOWN,
-        SCROLL_TO_SELECTED
+        SLIDE_DOWN//,
+        //SCROLL_TO_SELECTED
     };
 
     static const float scroll_speed;
@@ -32,9 +98,9 @@ private:
     int   mCols;
     int   mRows;
     float mSlide;            //[-1,1]. defines, the y-offset of the cards
-    float mScrollOffset;
+    InOutQuadEasing mScrollOffset;
     int   mCurrentSelection; //0 <= mCurrentSelection < mCards.size(). defines the current selected and thus upscaled card
-    int   mColsToScroll;  //the number of cols we need to scroll
+    //int   mColsToScroll;  //the number of cols we need to scroll
     AnimationStage mStage; // state machine state. for animation purposes
 };