calcDimensions(){
        if( this._breakpoint ) return;
        var dims = this.dimensions;
  
        // Container of sticky sidebar dimensions.
        dims.containerTop    = StickySidebar.offsetRelative(this.container).top;
        dims.containerHeight = this.container.clientHeight;
        dims.containerBottom = dims.containerTop + dims.containerHeight;
  
        // Sidebar dimensions.
        dims.sidebarHeight = this.sidebarInner.offsetHeight;
        dims.sidebarWidth  = this.sidebarInner.offsetWidth;
        
        // Screen viewport dimensions.
        dims.viewportHeight = window.innerHeight;

        // Maximum sidebar translate Y.
        dims.maxTranslateY = dims.containerHeight - dims.sidebarHeight;

        this._calcDimensionsWithScroll();
      }
Calculates dimensions of sidebar, container and screen viewpoint
@public