/** Sets the current stack scroll */
 public void setStackScroll(float s) {
   Log.d(TAG, "setStackScroll: ");
   mStackScrollP = s;
   if (mCb != null) {
     mCb.onScrollChanged(mStackScrollP);
   }
 }
 /** Called from the view draw, computes the next scroll. */
 boolean computeScroll() {
   Log.d(TAG, "computeScroll: ");
   if (mScroller.computeScrollOffset()) {
     float scroll = scrollRangeToProgress(mScroller.getCurrY());
     setStackScrollRaw(scroll);
     if (mCb != null) {
       mCb.onScrollChanged(scroll);
     }
     return true;
   }
   return false;
 }