text: export default class SelectionHelper {
  
  	constructor( selectionBox, renderer, cssClass ) {
  
  		this.element = document.createElement( "div" );
  		this.element.classList.add( cssClass );
  		this.element.style.pointerEvents = "none";
  		this.renderer = renderer;
  
  		this.startPoint = { x: 0, y: 0 };
  		this.pointTopLeft = { x: 0, y: 0 };
  		this.pointBottomRight = { x: 0, y: 0 };
  
  		this.isDown = false;
  
  		this.renderer.domElement.addEventListener( "mousedown", ( event ) => {
  
  			this.isDown = true;
  			this.onSelectStart( event );
  
  		}, false );
  
  		this.renderer.domElement.addEventListener( "mousemove", ( event ) => {
  
  			if ( this.isDown ) {
  
  				this.onSelectMove( event );
  
  			}
  
  		}, false );
  
  		this.renderer.domElement.addEventListener( "mouseup", ( event ) => {
  
  			this.isDown = false;
  			this.onSelectOver( event );
  
  		}, false );
  
  	}
  
  	onSelectStart( event ) {
  
  		this.renderer.domElement.parentElement.appendChild( this.element );
  		this.element.style.left = event.clientX + "px";
  		this.element.style.top = event.clientY + "px";
  		this.element.style.width = "0px";
  		this.element.style.height = "0px";
  		this.startPoint.x = event.clientX;
  		this.startPoint.y = event.clientY;
  
  	}
  
  	onSelectMove( event ) {
  
  		this.pointBottomRight.x = Math.max( this.startPoint.x, event.clientX );
  		this.pointBottomRight.y = Math.max( this.startPoint.y, event.clientY );
  		this.pointTopLeft.x = Math.min( this.startPoint.x, event.clientX );
  		this.pointTopLeft.y = Math.min( this.startPoint.y, event.clientY );
  
  		this.element.style.left = this.pointTopLeft.x + "px";
  		this.element.style.top = this.pointTopLeft.y + "px";
  		this.element.style.width = ( this.pointBottomRight.x - this.pointTopLeft.x ) + "px";
  		this.element.style.height = ( this.pointBottomRight.y - this.pointTopLeft.y ) + "px";
  
  	}
  
  	onSelectOver() {
  
  		this.element.parentElement.removeChild( this.element );
  
  	}
  
  }
  