private onGlobalDragEnter:(_event:DragEvent) => void = (_event) => {
    // When the global drag and drop is active and the dragging happens over the DOM
    // elements, the dragenter and dragleave events are always fired in pairs.
    // On dragenter the this.dragging is set to 2 and on dragleave we deduct it to 1,
    // meaning the drag and drop remains active. When the drag and drop action is canceled