question: private float calculateBasePageTargetY ( PanelState expandedState ) { if ( ! isFullscreenSizePanel ( ) ) return 0.f ; final float selectionY = mBasePageSelectionYPx * mPxToDp ; final float expandedHeight = getPanelHeightFromState ( expandedState ) - mSearchBarPaddingTop ; final float fullscreenHeight = getFullscreenHeight ( ) ; final float availableHeight = fullscreenHeight - expandedHeight ; float offset = - selectionY + availableHeight / 2 ; offset = Math . min ( offset , 0.f ) ; if ( mIsToolbarShowing ) offset -= mToolbarHeight ; offset = Math . max ( offset , - expandedHeight ) ; return offset ; }
target:  Calculates the target offset of the Base Page in order to keep the selection in view after expanding the Panel to the given |expandedState|.