text: import {
  	Matrix4,
  	Object3D,
  	Vector3
  } from 'three';
  
  class CSS2DObject extends Object3D {
  
  	constructor( element = document.createElement( 'div' ) ) {
  
  		super();
  
  		this.element = element;
  
  		this.element.style.position = 'absolute';
  		this.element.style.userSelect = 'none';
  
  		this.element.setAttribute( 'draggable', false );
  
  		this.addEventListener( 'removed', function () {
  
  			this.traverse( function ( object ) {
  
  				if ( object.element instanceof Element && object.element.parentNode !== null ) {
  
  					object.element.parentNode.removeChild( object.element );
  
  				}
  
  			} );
  
  		} );
  
  	}
  
  	copy( source, recursive ) {
  
  		super.copy( source, recursive );
  
  		this.element = source.element.cloneNode( true );
  
  		return this;
  
  	}
  
  }
  
  CSS2DObject.prototype.isCSS2DObject = true;
  
  //
  
  const _vector = new Vector3();
  const _viewMatrix = new Matrix4();
  const _viewProjectionMatrix = new Matrix4();
  const _a = new Vector3();
  const _b = new Vector3();
  
  class CSS2DRenderer {
  
  	constructor( parameters = {} ) {
  
  		const _this = this;
  
  		let _width, _height;
  		let _widthHalf, _heightHalf;
  
  		const cache = {
  			objects: new WeakMap()
  		};
  
  		const domElement = parameters.element !== undefined ? parameters.element : document.createElement( 'div' );
  
  		domElement.style.overflow = 'hidden';
  
  		this.domElement = domElement;
  
  		this.getSize = function () {
  
  			return {
  				width: _width,
  				height: _height
  			};
  
  		};
  
  		this.render = function ( scene, camera ) {
  
  			if ( scene.autoUpdate === true ) scene.updateMatrixWorld();
  			if ( camera.parent === null ) camera.updateMatrixWorld();
  
  			_viewMatrix.copy( camera.matrixWorldInverse );
  			_viewProjectionMatrix.multiplyMatrices( camera.projectionMatrix, _viewMatrix );
  
  			renderObject( scene, scene, camera );
  			zOrder( scene );
  
  		};
  
  		this.setSize = function ( width, height ) {
  
  			_width = width;
  			_height = height;
  
  			_widthHalf = _width / 2;
  			_heightHalf = _height / 2;
  
  			domElement.style.width = width + 'px';
  			domElement.style.height = height + 'px';
  
  		};
  
  		function renderObject( object, scene, camera ) {
  
  			if ( object.isCSS2DObject ) {
  
  				const visible = object.visible && _vector.z >= - 1 && _vector.z <= 1 && object.layers.test( camera.layers );
  				object.element.style.display = visible ? '' : 'none';
  
  				if ( visible ) {
  
  					object.onBeforeRender( _this, scene, camera );
  
  					_vector.setFromMatrixPosition( object.matrixWorld );
  					_vector.applyMatrix4( _viewProjectionMatrix );
  
  					const element = object.element;
  
  					if ( /apple/i.test( navigator.vendor ) ) {
  
  						// https://github.com/mrdoob/three.js/issues/21415
  						element.style.transform = 'translate(-50%,-50%) translate(' + Math.round( _vector.x * _widthHalf + _widthHalf ) + 'px,' + Math.round( - _vector.y * _heightHalf + _heightHalf ) + 'px)';
  
  					} else {
  
  						element.style.transform = 'translate(-50%,-50%) translate(' + ( _vector.x * _widthHalf + _widthHalf ) + 'px,' + ( - _vector.y * _heightHalf + _heightHalf ) + 'px)';
  
  					}
  
  					if ( element.parentNode !== domElement ) {
  
  						domElement.appendChild( element );
  
  					}
  
  					object.onAfterRender( _this, scene, camera );
  
  				}
  
  				const objectData = {
  					distanceToCameraSquared: getDistanceToSquared( camera, object )
  				};
  
  				cache.objects.set( object, objectData );
  
  			}
  
  			for ( let i = 0, l = object.children.length; i < l; i ++ ) {
  
  				renderObject( object.children[ i ], scene, camera );
  
  			}
  
  		}
  
  		function getDistanceToSquared( object1, object2 ) {
  
  			_a.setFromMatrixPosition( object1.matrixWorld );
  			_b.setFromMatrixPosition( object2.matrixWorld );
  
  			return _a.distanceToSquared( _b );
  
  		}
  
  		function filterAndFlatten( scene ) {
  
  			const result = [];
  
  			scene.traverse( function ( object ) {
  
  				if ( object.isCSS2DObject ) result.push( object );
  
  			} );
  
  			return result;
  
  		}
  
  		function zOrder( scene ) {
  
  			const sorted = filterAndFlatten( scene ).sort( function ( a, b ) {
  
  				if ( a.renderOrder !== b.renderOrder ) {
  
  					return b.renderOrder - a.renderOrder;
  
  				}
  
  				const distanceA = cache.objects.get( a ).distanceToCameraSquared;
  				const distanceB = cache.objects.get( b ).distanceToCameraSquared;
  
  				return distanceA - distanceB;
  
  			} );
  
  			const zMax = sorted.length;
  
  			for ( let i = 0, l = sorted.length; i < l; i ++ ) {
  
  				sorted[ i ].element.style.zIndex = zMax - i;
  
  			}
  
  		}
  
  	}
  
  }
  
  export { CSS2DObject, CSS2DRenderer };
  