dc-sdk/src/modules/exts/Viewer.js

/**
 * @Author : Caven Chen
 */

import { Cesium } from '../../namespace'
const {
  BoundingSphere,
  BoundingSphereState,
  Cartographic,
  CesiumWidget,
  Cesium3DTileset,
  Clock,
  computeFlyToLocationForRectangle,
  DataSourceCollection,
  DataSourceDisplay,
  defaultValue,
  defined,
  destroyObject,
  DeveloperError,
  Entity,
  EntityView,
  Event,
  EventHelper,
  getElement,
  HeadingPitchRange,
  ImageryLayer,
  Matrix4,
  Property,
  SceneMode,
  ScreenSpaceEventType,
  TimeDynamicPointCloud,
  VoxelPrimitive,
  Color,
} = Cesium

const boundingSphereScratch = new BoundingSphere()

function trackDataSourceClock(timeline, clock, dataSource) {
  if (defined(dataSource)) {
    const dataSourceClock = dataSource.clock
    if (defined(dataSourceClock)) {
      dataSourceClock.getValue(clock)
    }
  }
}

/**
 * @typedef {object} Viewer.ConstructorOptions
 *
 * Initialization options for the Viewer constructor
 *
 * @property {ImageryProvider|false} [imageryProvider=createWorldImagery()] The imagery provider to use.  This value is only valid if `baseLayerPicker` is set to false. Deprecated.
 * @property {ImageryLayer|false} [baseLayer=ImageryLayer.fromWorldImagery()] The bottommost imagery layer applied to the globe. If set to <code>false</code>, no imagery provider will be added. This value is only valid if `baseLayerPicker` is set to false.
 * @property {TerrainProvider} [terrainProvider=new EllipsoidTerrainProvider()] The terrain provider to use
 * @property {Terrain} [terrain] A terrain object which handles asynchronous terrain provider. Can only specify if options.terrainProvider is undefined.
 * @property {SkyBox|false} [skyBox] The skybox used to render the stars.  When <code>undefined</code>, the default stars are used. If set to <code>false</code>, no skyBox, Sun, or Moon will be added.
 * @property {SkyAtmosphere|false} [skyAtmosphere] Blue sky, and the glow around the Earth's limb.  Set to <code>false</code> to turn it off.
 * @property {Element|string} [fullscreenElement=document.body] The element or id to be placed into fullscreen mode when the full screen button is pressed.
 * @property {boolean} [useDefaultRenderLoop=true] True if this widget should control the render loop, false otherwise.
 * @property {number} [targetFrameRate] The target frame rate when using the default render loop.
 * @property {boolean} [showRenderLoopErrors=true] If true, this widget will automatically display an HTML panel to the user containing the error, if a render loop error occurs.
 * @property {boolean} [useBrowserRecommendedResolution=true] If true, render at the browser's recommended resolution and ignore <code>window.devicePixelRatio</code>.
 * @property {boolean} [automaticallyTrackDataSourceClocks=true] If true, this widget will automatically track the clock settings of newly added DataSources, updating if the DataSource's clock changes.  Set this to false if you want to configure the clock independently.
 * @property {ContextOptions} [contextOptions] Context and WebGL creation properties passed to {@link Scene}.
 * @property {SceneMode} [sceneMode=SceneMode.SCENE3D] The initial scene mode.
 * @property {MapProjection} [mapProjection=new GeographicProjection()] The map projection to use in 2D and Columbus View modes.
 * @property {Globe|false} [globe=new Globe(mapProjection.ellipsoid)] The globe to use in the scene.  If set to <code>false</code>, no globe will be added and the sky atmosphere will be hidden by default.
 * @property {boolean} [orderIndependentTranslucency=true] If true and the configuration supports it, use order independent translucency.
 * @property {Element|string} [creditContainer] The DOM element or ID that will contain the {@link CreditDisplay}.  If not specified, the credits are added to the bottom of the widget itself.
 * @property {Element|string} [creditViewport] The DOM element or ID that will contain the credit pop up created by the {@link CreditDisplay}.  If not specified, it will appear over the widget itself.
 * @property {DataSourceCollection} [dataSources=new DataSourceCollection()] The collection of data sources visualized by the widget.  If this parameter is provided,
 *                               the instance is assumed to be owned by the caller and will not be destroyed when the viewer is destroyed.
 * @property {boolean} [shadows=false] Determines if shadows are cast by light sources.
 * @property {ShadowMode} [terrainShadows=ShadowMode.RECEIVE_ONLY] Determines if the terrain casts or receives shadows from light sources.
 * @property {MapMode2D} [mapMode2D=MapMode2D.INFINITE_SCROLL] Determines if the 2D map is rotatable or can be scrolled infinitely in the horizontal direction.
 * @property {boolean} [projectionPicker=false] If set to true, the ProjectionPicker widget will be created.
 * @property {boolean} [blurActiveElementOnCanvasFocus=true] If true, the active element will blur when the viewer's canvas is clicked. Setting this to false is useful for cases when the canvas is clicked only for retrieving position or an entity data without actually meaning to set the canvas to be the active element.
 * @property {boolean} [requestRenderMode=false] If true, rendering a frame will only occur when needed as determined by changes within the scene. Enabling reduces the CPU/GPU usage of your application and uses less battery on mobile, but requires using {@link Scene#requestRender} to render a new frame explicitly in this mode. This will be necessary in many cases after making changes to the scene in other parts of the API. See {@link https://cesium.com/blog/2018/01/24/cesium-scene-rendering-performance/|Improving Performance with Explicit Rendering}.
 * @property {number} [maximumRenderTimeChange=0.0] If requestRenderMode is true, this value defines the maximum change in simulation time allowed before a render is requested. See {@link https://cesium.com/blog/2018/01/24/cesium-scene-rendering-performance/|Improving Performance with Explicit Rendering}.
 * @property {number} [depthPlaneEllipsoidOffset=0.0] Adjust the DepthPlane to address rendering artefacts below ellipsoid zero elevation.
 * @property {number} [msaaSamples=1] If provided, this value controls the rate of multisample antialiasing. Typical multisampling rates are 2, 4, and sometimes 8 samples per pixel. Higher sampling rates of MSAA may impact performance in exchange for improved visual quality. This value only applies to WebGL2 contexts that support multisample render targets.
 */

/**
 * A base widget for building applications.  It composites all of the standard Cesium widgets into one reusable package.
 * The widget can always be extended by using mixins, which add functionality useful for a variety of applications.
 *
 * @alias Viewer
 * @constructor
 *
 * @param {Element|string} container The DOM element or ID that will contain the widget.
 * @param {Viewer.ConstructorOptions} [options] Object describing initialization options
 *
 * @exception {DeveloperError} Element with id "container" does not exist in the document.
 * @exception {DeveloperError} options.selectedImageryProviderViewModel is not available when not using the BaseLayerPicker widget, specify options.baseLayer instead.
 * @exception {DeveloperError} options.selectedTerrainProviderViewModel is not available when not using the BaseLayerPicker widget, specify options.terrainProvider instead.
 *
 * @see Animation
 * @see BaseLayerPicker
 * @see CesiumWidget
 * @see FullscreenButton
 * @see HomeButton
 * @see SceneModePicker
 * @see Timeline
 * @see viewerDragDropMixin
 *
 * @demo {@link https://sandcastle.cesium.com/index.html?src=Hello%20World.html|Cesium Sandcastle Hello World Demo}
 *
 * @example
 * // Initialize the viewer widget with several custom options and mixins.
 * try {
 *   const viewer = new Cesium.Viewer("cesiumContainer", {
 *     // Start in Columbus Viewer
 *     sceneMode: Cesium.SceneMode.COLUMBUS_VIEW,
 *     // Use Cesium World Terrain
 *     terrain: Cesium.Terrain.fromWorldTerrain(),
 *     // Hide the base layer picker
 *     baseLayerPicker: false,
 *     // Use OpenStreetMaps
 *     baseLayer: new Cesium.ImageryLayer(new Cesium.OpenStreetMapImageryProvider({
 *       url: "https://tile.openstreetmap.org/"
 *     })),
 *     skyBox: new Cesium.SkyBox({
 *       sources: {
 *         positiveX: "stars/TychoSkymapII.t3_08192x04096_80_px.jpg",
 *         negativeX: "stars/TychoSkymapII.t3_08192x04096_80_mx.jpg",
 *         positiveY: "stars/TychoSkymapII.t3_08192x04096_80_py.jpg",
 *         negativeY: "stars/TychoSkymapII.t3_08192x04096_80_my.jpg",
 *         positiveZ: "stars/TychoSkymapII.t3_08192x04096_80_pz.jpg",
 *         negativeZ: "stars/TychoSkymapII.t3_08192x04096_80_mz.jpg"
 *       }
 *     }),
 *     // Show Columbus View map with Web Mercator projection
 *     mapProjection: new Cesium.WebMercatorProjection()
 *   });
 * } catch (error) {
 *   console.log(error);
 * }
 *
 * // Add basic drag and drop functionality
 * viewer.extend(Cesium.viewerDragDropMixin);
 *
 * // Show a pop-up alert if we encounter an error when processing a dropped file
 * viewer.dropError.addEventListener(function(dropHandler, name, error) {
 *   console.log(error);
 *   window.alert(error);
 * });
 */
function Viewer(container, options) {
  //>>includeStart('debug', pragmas.debug);
  if (!defined(container)) {
    throw new DeveloperError('container is required.')
  }
  //>>includeEnd('debug');

  container = getElement(container)
  options = defaultValue(options, defaultValue.EMPTY_OBJECT)

  const scene3DOnly = defaultValue(options.scene3DOnly, false)

  let clock = new Clock()

  if (defined(options.shouldAnimate)) {
    clock.shouldAnimate = options.shouldAnimate
  }

  // Cesium widget
  const cesiumWidget = new CesiumWidget(container, {
    baseLayer: false,
    clock: clock,
    skyBox: options.skyBox,
    skyAtmosphere: options.skyAtmosphere,
    sceneMode: options.sceneMode,
    mapProjection: options.mapProjection,
    globe: options.globe,
    orderIndependentTranslucency: options.orderIndependentTranslucency,
    contextOptions: options.contextOptions,
    useDefaultRenderLoop: options.useDefaultRenderLoop,
    targetFrameRate: options.targetFrameRate,
    showRenderLoopErrors: options.showRenderLoopErrors,
    useBrowserRecommendedResolution: options.useBrowserRecommendedResolution,
    creditContainer: document.createElement('div'),
    creditViewport: document.createElement('div'),
    scene3DOnly: scene3DOnly,
    shadows: options.shadows,
    terrainShadows: options.terrainShadows,
    mapMode2D: options.mapMode2D,
    blurActiveElementOnCanvasFocus: options.blurActiveElementOnCanvasFocus,
    requestRenderMode: options.requestRenderMode,
    maximumRenderTimeChange: options.maximumRenderTimeChange,
    depthPlaneEllipsoidOffset: options.depthPlaneEllipsoidOffset,
    msaaSamples: options.msaaSamples,
  })

  cesiumWidget.scene.backgroundColor = Color.TRANSPARENT
  cesiumWidget.canvas.parentNode.className = 'viewer-canvas'

  let dataSourceCollection = options.dataSources
  let destroyDataSourceCollection = false
  if (!defined(dataSourceCollection)) {
    dataSourceCollection = new DataSourceCollection()
    destroyDataSourceCollection = true
  }

  const scene = cesiumWidget.scene

  scene.screenSpaceCameraController.maximumZoomDistance = 40489014.0

  const dataSourceDisplay = new DataSourceDisplay({
    scene: scene,
    dataSourceCollection: dataSourceCollection,
  })

  const eventHelper = new EventHelper()

  eventHelper.add(clock.onTick, Viewer.prototype._onTick, this)
  eventHelper.add(scene.morphStart, Viewer.prototype._clearTrackedObject, this)

  // Main Toolbar
  const toolbar = document.createElement('div')

  //Assign all properties to this instance.  No "this" assignments should
  //take place above this line.
  this._dataSourceChangedListeners = {}
  this._automaticallyTrackDataSourceClocks = defaultValue(
    options.automaticallyTrackDataSourceClocks,
    true
  )

  this._clock = clock
  this._container = container
  this._bottomContainer = document.createElement('div')
  this._element = document.createElement('div')
  this._cesiumWidget = cesiumWidget
  this._dataSourceCollection = dataSourceCollection
  this._destroyDataSourceCollection = destroyDataSourceCollection
  this._dataSourceDisplay = dataSourceDisplay
  this._toolbar = toolbar
  this._eventHelper = eventHelper
  this._lastWidth = 0
  this._lastHeight = 0
  this._allowDataSourcesToSuspendAnimation = true
  this._entityView = undefined
  this._enableInfoOrSelection = false
  this._clockTrackedDataSource = undefined
  this._trackedEntity = undefined
  this._needTrackedEntityUpdate = false
  this._selectedEntity = undefined
  this._zoomIsFlight = false
  this._zoomTarget = undefined
  this._zoomPromise = undefined
  this._zoomOptions = undefined
  this._selectedEntityChanged = new Event()
  this._trackedEntityChanged = new Event()

  //Listen to data source events in order to track clock changes.
  eventHelper.add(
    dataSourceCollection.dataSourceAdded,
    Viewer.prototype._onDataSourceAdded,
    this
  )
  eventHelper.add(
    dataSourceCollection.dataSourceRemoved,
    Viewer.prototype._onDataSourceRemoved,
    this
  )

  // Prior to each render, check if anything needs to be resized.
  eventHelper.add(scene.postUpdate, Viewer.prototype.resize, this)
  eventHelper.add(scene.postRender, Viewer.prototype._postRender, this)

  // We need to subscribe to the data sources and collections so that we can clear the
  // tracked object when it is removed from the scene.
  // Subscribe to current data sources
  const dataSourceLength = dataSourceCollection.length
  for (let i = 0; i < dataSourceLength; i++) {
    this._dataSourceAdded(dataSourceCollection, dataSourceCollection.get(i))
  }
  this._dataSourceAdded(undefined, dataSourceDisplay.defaultDataSource)

  // Hook up events so that we can subscribe to future sources.
  eventHelper.add(
    dataSourceCollection.dataSourceAdded,
    Viewer.prototype._dataSourceAdded,
    this
  )
  eventHelper.add(
    dataSourceCollection.dataSourceRemoved,
    Viewer.prototype._dataSourceRemoved,
    this
  )
}

/**
 *
 */
Object.defineProperties(Viewer.prototype, {
  /**
   * Gets the parent container.
   * @memberof Viewer.prototype
   * @type {Element}
   * @readonly
   */
  container: {
    get: function () {
      return this._container
    },
  },

  /**
   * Gets the DOM element for the area at the bottom of the window containing the
   * {@link CreditDisplay} and potentially other things.
   * @memberof Viewer.prototype
   * @type {Element}
   * @readonly
   */
  bottomContainer: {
    get: function () {
      return this._bottomContainer
    },
  },

  /**
   * Gets the CesiumWidget.
   * @memberof Viewer.prototype
   * @type {CesiumWidget}
   * @readonly
   */
  cesiumWidget: {
    get: function () {
      return this._cesiumWidget
    },
  },

  /**
   * Gets the display used for {@link DataSource} visualization.
   * @memberof Viewer.prototype
   * @type {DataSourceDisplay}
   * @readonly
   */
  dataSourceDisplay: {
    get: function () {
      return this._dataSourceDisplay
    },
  },

  /**
   * Gets the collection of entities not tied to a particular data source.
   * This is a shortcut to [dataSourceDisplay.defaultDataSource.entities]{@link Viewer#dataSourceDisplay}.
   * @memberof Viewer.prototype
   * @type {EntityCollection}
   * @readonly
   */
  entities: {
    get: function () {
      return this._dataSourceDisplay.defaultDataSource.entities
    },
  },

  /**
   * Gets the set of {@link DataSource} instances to be visualized.
   * @memberof Viewer.prototype
   * @type {DataSourceCollection}
   * @readonly
   */
  dataSources: {
    get: function () {
      return this._dataSourceCollection
    },
  },

  /**
   * Gets the canvas.
   * @memberof Viewer.prototype
   * @type {HTMLCanvasElement}
   * @readonly
   */
  canvas: {
    get: function () {
      return this._cesiumWidget.canvas
    },
  },

  /**
   * Gets the scene.
   * @memberof Viewer.prototype
   * @type {Scene}
   * @readonly
   */
  scene: {
    get: function () {
      return this._cesiumWidget.scene
    },
  },

  /**
   * Determines if shadows are cast by light sources.
   * @memberof Viewer.prototype
   * @type {boolean}
   */
  shadows: {
    get: function () {
      return this.scene.shadowMap.enabled
    },
    set: function (value) {
      this.scene.shadowMap.enabled = value
    },
  },

  /**
   * Determines if the terrain casts or shadows from light sources.
   * @memberof Viewer.prototype
   * @type {ShadowMode}
   */
  terrainShadows: {
    get: function () {
      return this.scene.globe.shadows
    },
    set: function (value) {
      this.scene.globe.shadows = value
    },
  },

  /**
   * Get the scene's shadow map
   * @memberof Viewer.prototype
   * @type {ShadowMap}
   * @readonly
   */
  shadowMap: {
    get: function () {
      return this.scene.shadowMap
    },
  },

  /**
   * Gets the collection of image layers that will be rendered on the globe.
   * @memberof Viewer.prototype
   *
   * @type {ImageryLayerCollection}
   * @readonly
   */
  imageryLayers: {
    get: function () {
      return this.scene.imageryLayers
    },
  },

  /**
   * The terrain provider providing surface geometry for the globe.
   * @memberof Viewer.prototype
   *
   * @type {TerrainProvider}
   */
  terrainProvider: {
    get: function () {
      return this.scene.terrainProvider
    },
    set: function (terrainProvider) {
      this.scene.terrainProvider = terrainProvider
    },
  },

  /**
   * Gets the camera.
   * @memberof Viewer.prototype
   *
   * @type {Camera}
   * @readonly
   */
  camera: {
    get: function () {
      return this.scene.camera
    },
  },

  /**
   * Gets the post-process stages.
   * @memberof Viewer.prototype
   *
   * @type {PostProcessStageCollection}
   * @readonly
   */
  postProcessStages: {
    get: function () {
      return this.scene.postProcessStages
    },
  },

  /**
   * Gets the clock.
   * @memberof Viewer.prototype
   * @type {Clock}
   * @readonly
   */
  clock: {
    get: function () {
      return this._clock
    },
  },

  /**
   * Gets the screen space event handler.
   * @memberof Viewer.prototype
   * @type {ScreenSpaceEventHandler}
   * @readonly
   */
  screenSpaceEventHandler: {
    get: function () {
      return this._cesiumWidget.screenSpaceEventHandler
    },
  },

  /**
   * Gets or sets the target frame rate of the widget when <code>useDefaultRenderLoop</code>
   * is true. If undefined, the browser's requestAnimationFrame implementation
   * determines the frame rate.  If defined, this value must be greater than 0.  A value higher
   * than the underlying requestAnimationFrame implementation will have no effect.
   * @memberof Viewer.prototype
   *
   * @type {number}
   */
  targetFrameRate: {
    get: function () {
      return this._cesiumWidget.targetFrameRate
    },
    set: function (value) {
      this._cesiumWidget.targetFrameRate = value
    },
  },

  /**
   * Gets or sets whether or not this widget should control the render loop.
   * If true the widget will use requestAnimationFrame to
   * perform rendering and resizing of the widget, as well as drive the
   * simulation clock. If set to false, you must manually call the
   * <code>resize</code>, <code>render</code> methods
   * as part of a custom render loop.  If an error occurs during rendering, {@link Scene}'s
   * <code>renderError</code> event will be raised and this property
   * will be set to false.  It must be set back to true to continue rendering
   * after the error.
   * @memberof Viewer.prototype
   *
   * @type {boolean}
   */
  useDefaultRenderLoop: {
    get: function () {
      return this._cesiumWidget.useDefaultRenderLoop
    },
    set: function (value) {
      this._cesiumWidget.useDefaultRenderLoop = value
    },
  },

  /**
   * Gets or sets a scaling factor for rendering resolution.  Values less than 1.0 can improve
   * performance on less powerful devices while values greater than 1.0 will render at a higher
   * resolution and then scale down, resulting in improved visual fidelity.
   * For example, if the widget is laid out at a size of 640x480, setting this value to 0.5
   * will cause the scene to be rendered at 320x240 and then scaled up while setting
   * it to 2.0 will cause the scene to be rendered at 1280x960 and then scaled down.
   * @memberof Viewer.prototype
   *
   * @type {number}
   * @default 1.0
   */
  resolutionScale: {
    get: function () {
      return this._cesiumWidget.resolutionScale
    },
    set: function (value) {
      this._cesiumWidget.resolutionScale = value
    },
  },

  /**
   * Boolean flag indicating if the browser's recommended resolution is used.
   * If true, the browser's device pixel ratio is ignored and 1.0 is used instead,
   * effectively rendering based on CSS pixels instead of device pixels. This can improve
   * performance on less powerful devices that have high pixel density. When false, rendering
   * will be in device pixels. {@link Viewer#resolutionScale} will still take effect whether
   * this flag is true or false.
   * @memberof Viewer.prototype
   *
   * @type {boolean}
   * @default true
   */
  useBrowserRecommendedResolution: {
    get: function () {
      return this._cesiumWidget.useBrowserRecommendedResolution
    },
    set: function (value) {
      this._cesiumWidget.useBrowserRecommendedResolution = value
    },
  },

  /**
   * Gets or sets whether or not data sources can temporarily pause
   * animation in order to avoid showing an incomplete picture to the user.
   * For example, if asynchronous primitives are being processed in the
   * background, the clock will not advance until the geometry is ready.
   *
   * @memberof Viewer.prototype
   *
   * @type {boolean}
   */
  allowDataSourcesToSuspendAnimation: {
    get: function () {
      return this._allowDataSourcesToSuspendAnimation
    },
    set: function (value) {
      this._allowDataSourcesToSuspendAnimation = value
    },
  },

  /**
   * Gets or sets the Entity instance currently being tracked by the camera.
   * @memberof Viewer.prototype
   * @type {Entity | undefined}
   */
  trackedEntity: {
    get: function () {
      return this._trackedEntity
    },
    set: function (value) {
      if (this._trackedEntity !== value) {
        this._trackedEntity = value

        //Cancel any pending zoom
        cancelZoom(this)

        const scene = this.scene
        const sceneMode = scene.mode

        //Stop tracking
        if (!defined(value) || !defined(value.position)) {
          this._needTrackedEntityUpdate = false
          if (
            sceneMode === SceneMode.COLUMBUS_VIEW ||
            sceneMode === SceneMode.SCENE2D
          ) {
            scene.screenSpaceCameraController.enableTranslate = true
          }

          if (
            sceneMode === SceneMode.COLUMBUS_VIEW ||
            sceneMode === SceneMode.SCENE3D
          ) {
            scene.screenSpaceCameraController.enableTilt = true
          }

          this._entityView = undefined
          this.camera.lookAtTransform(Matrix4.IDENTITY)
        } else {
          //We can't start tracking immediately, so we set a flag and start tracking
          //when the bounding sphere is ready (most likely next frame).
          this._needTrackedEntityUpdate = true
        }

        this._trackedEntityChanged.raiseEvent(value)
        this.scene.requestRender()
      }
    },
  },
  /**
   * Gets or sets the object instance for which to display a selection indicator.
   *
   * If a user interactively picks a Cesium3DTilesFeature instance, then this property
   * will contain a transient Entity instance with a property named "feature" that is
   * the instance that was picked.
   * @memberof Viewer.prototype
   * @type {Entity | undefined}
   */
  selectedEntity: {
    get: function () {
      return this._selectedEntity
    },
    set: function (value) {
      if (this._selectedEntity !== value) {
        this._selectedEntity = value
        this._selectedEntityChanged.raiseEvent(value)
      }
    },
  },
  /**
   * Gets the event that is raised when the selected entity changes.
   * @memberof Viewer.prototype
   * @type {Event}
   * @readonly
   */
  selectedEntityChanged: {
    get: function () {
      return this._selectedEntityChanged
    },
  },
  /**
   * Gets the event that is raised when the tracked entity changes.
   * @memberof Viewer.prototype
   * @type {Event}
   * @readonly
   */
  trackedEntityChanged: {
    get: function () {
      return this._trackedEntityChanged
    },
  },
  /**
   * Gets or sets the data source to track with the viewer's clock.
   * @memberof Viewer.prototype
   * @type {DataSource}
   */
  clockTrackedDataSource: {
    get: function () {
      return this._clockTrackedDataSource
    },
    set: function (value) {
      if (this._clockTrackedDataSource !== value) {
        this._clockTrackedDataSource = value
        trackDataSourceClock(undefined, this.clock, value)
      }
    },
  },
})

/**
 * Extends the base viewer functionality with the provided mixin.
 * A mixin may add additional properties, functions, or other behavior
 * to the provided viewer instance.
 *
 * @param {Viewer.ViewerMixin} mixin The Viewer mixin to add to this instance.
 * @param {object} [options] The options object to be passed to the mixin function.
 *
 * @see viewerDragDropMixin
 */
Viewer.prototype.extend = function (mixin, options) {
  //>>includeStart('debug', pragmas.debug);
  if (!defined(mixin)) {
    throw new DeveloperError('mixin is required.')
  }
  //>>includeEnd('debug')

  mixin(this, options)
}

/**
 * Resizes the widget to match the container size.
 * This function is called automatically as needed unless
 * <code>useDefaultRenderLoop</code> is set to false.
 */
Viewer.prototype.resize = function () {
  const cesiumWidget = this._cesiumWidget
  const container = this._container
  const width = container.clientWidth
  const height = container.clientHeight
  cesiumWidget.resize()
  if (width === this._lastWidth && height === this._lastHeight) {
    return
  }
  this._lastWidth = width
  this._lastHeight = height
}

/**
 * This forces the widget to re-think its layout, including
 * widget sizes and credit placement.
 */
Viewer.prototype.forceResize = function () {
  this._lastWidth = 0
  this.resize()
}

/**
 * Renders the scene.  This function is called automatically
 * unless <code>useDefaultRenderLoop</code> is set to false;
 */
Viewer.prototype.render = function () {
  this._cesiumWidget.render()
}

/**
 * @returns {boolean} true if the object has been destroyed, false otherwise.
 */
Viewer.prototype.isDestroyed = function () {
  return false
}

/**
 * Destroys the widget.  Should be called if permanently
 * removing the widget from layout.
 */
Viewer.prototype.destroy = function () {
  if (this.isDestroyed()) {
    return undefined
  }

  let i

  if (
    defined(this.screenSpaceEventHandler) &&
    !this.screenSpaceEventHandler.isDestroyed()
  ) {
    this.screenSpaceEventHandler.removeInputAction(
      ScreenSpaceEventType.LEFT_CLICK
    )
    this.screenSpaceEventHandler.removeInputAction(
      ScreenSpaceEventType.LEFT_DOUBLE_CLICK
    )
  }

  // Unsubscribe from data sources
  const dataSources = this.dataSources
  const dataSourceLength = dataSources.length
  for (i = 0; i < dataSourceLength; i++) {
    this._dataSourceRemoved(dataSources, dataSources.get(i))
  }
  this._dataSourceRemoved(undefined, this._dataSourceDisplay.defaultDataSource)

  this._eventHelper.removeAll()

  this._dataSourceDisplay = this._dataSourceDisplay.destroy()
  this._cesiumWidget = this._cesiumWidget.destroy()

  if (this._destroyDataSourceCollection) {
    this._dataSourceCollection = this._dataSourceCollection.destroy()
  }

  return destroyObject(this)
}

/**
 * @private
 */
Viewer.prototype._dataSourceAdded = function (
  dataSourceCollection,
  dataSource
) {
  const entityCollection = dataSource.entities
  entityCollection.collectionChanged.addEventListener(
    Viewer.prototype._onEntityCollectionChanged,
    this
  )
}

/**
 * @private
 */
Viewer.prototype._dataSourceRemoved = function (
  dataSourceCollection,
  dataSource
) {
  const entityCollection = dataSource.entities
  entityCollection.collectionChanged.removeEventListener(
    Viewer.prototype._onEntityCollectionChanged,
    this
  )

  if (defined(this.trackedEntity)) {
    if (
      entityCollection.getById(this.trackedEntity.id) === this.trackedEntity
    ) {
      this.trackedEntity = undefined
    }
  }

  if (defined(this.selectedEntity)) {
    if (
      entityCollection.getById(this.selectedEntity.id) === this.selectedEntity
    ) {
      this.selectedEntity = undefined
    }
  }
}

/**
 * @private
 */
Viewer.prototype._onTick = function (clock) {
  const time = clock.currentTime

  const isUpdated = this._dataSourceDisplay.update(time)
  if (this._allowDataSourcesToSuspendAnimation) {
    this._clock.canAnimate = isUpdated
  }

  const entityView = this._entityView
  if (defined(entityView)) {
    const trackedEntity = this._trackedEntity
    const trackedState = this._dataSourceDisplay.getBoundingSphere(
      trackedEntity,
      false,
      boundingSphereScratch
    )
    if (trackedState === BoundingSphereState.DONE) {
      entityView.update(time, boundingSphereScratch)
    }
  }

  let position
  let enableCamera = false
  const selectedEntity = this.selectedEntity
  const showSelection = defined(selectedEntity) && this._enableInfoOrSelection

  if (
    showSelection &&
    selectedEntity.isShowing &&
    selectedEntity.isAvailable(time)
  ) {
    const state = this._dataSourceDisplay.getBoundingSphere(
      selectedEntity,
      true,
      boundingSphereScratch
    )
    if (state !== BoundingSphereState.FAILED) {
      position = boundingSphereScratch.center
    } else if (defined(selectedEntity.position)) {
      position = selectedEntity.position.getValue(time, position)
    }
    enableCamera = defined(position)
  }
}

/**
 * @private
 */
Viewer.prototype._onEntityCollectionChanged = function (
  collection,
  added,
  removed
) {
  const length = removed.length
  for (let i = 0; i < length; i++) {
    const removedObject = removed[i]
    if (this.trackedEntity === removedObject) {
      this.trackedEntity = undefined
    }
    if (this.selectedEntity === removedObject) {
      this.selectedEntity = undefined
    }
  }
}

/**
 * @private
 */
Viewer.prototype._onInfoBoxCameraClicked = function (infoBoxViewModel) {
  if (
    infoBoxViewModel.isCameraTracking &&
    this.trackedEntity === this.selectedEntity
  ) {
    this.trackedEntity = undefined
  } else {
    const selectedEntity = this.selectedEntity
    const position = selectedEntity.position
    if (defined(position)) {
      this.trackedEntity = this.selectedEntity
    } else {
      this.zoomTo(this.selectedEntity)
    }
  }
}

/**
 * @private
 */
Viewer.prototype._clearTrackedObject = function () {
  this.trackedEntity = undefined
}

/**
 * @private
 */
Viewer.prototype._clearObjects = function () {
  this.trackedEntity = undefined
  this.selectedEntity = undefined
}

/**
 * @private
 */
Viewer.prototype._onDataSourceChanged = function (dataSource) {
  if (this.clockTrackedDataSource === dataSource) {
    trackDataSourceClock(undefined, this.clock, dataSource)
  }
}

/**
 * @private
 */
Viewer.prototype._onDataSourceAdded = function (
  dataSourceCollection,
  dataSource
) {
  if (this._automaticallyTrackDataSourceClocks) {
    this.clockTrackedDataSource = dataSource
  }
  const id = dataSource.entities.id
  const removalFunc = this._eventHelper.add(
    dataSource.changedEvent,
    Viewer.prototype._onDataSourceChanged,
    this
  )
  this._dataSourceChangedListeners[id] = removalFunc
}

/**
 * @private
 */
Viewer.prototype._onDataSourceRemoved = function (
  dataSourceCollection,
  dataSource
) {
  const resetClock = this.clockTrackedDataSource === dataSource
  const id = dataSource.entities.id
  this._dataSourceChangedListeners[id]()
  this._dataSourceChangedListeners[id] = undefined
  if (resetClock) {
    const numDataSources = dataSourceCollection.length
    if (this._automaticallyTrackDataSourceClocks && numDataSources > 0) {
      this.clockTrackedDataSource = dataSourceCollection.get(numDataSources - 1)
    } else {
      this.clockTrackedDataSource = undefined
    }
  }
}

/**
 * Asynchronously sets the camera to view the provided entity, entities, or data source.
 * If the data source is still in the process of loading or the visualization is otherwise still loading,
 * this method waits for the data to be ready before performing the zoom.
 *
 * <p>The offset is heading/pitch/range in the local east-north-up reference frame centered at the center of the bounding sphere.
 * The heading and the pitch angles are defined in the local east-north-up reference frame.
 * The heading is the angle from y axis and increasing towards the x axis. Pitch is the rotation from the xy-plane. Positive pitch
 * angles are above the plane. Negative pitch angles are below the plane. The range is the distance from the center. If the range is
 * zero, a range will be computed such that the whole bounding sphere is visible.</p>
 *
 * <p>In 2D, there must be a top down view. The camera will be placed above the target looking down. The height above the
 * target will be the range. The heading will be determined from the offset. If the heading cannot be
 * determined from the offset, the heading will be north.</p>
 *
 * @param {Entity|Entity[]|EntityCollection|DataSource|ImageryLayer|Cesium3DTileset|TimeDynamicPointCloud|Promise<Entity|Entity[]|EntityCollection|DataSource|ImageryLayer|Cesium3DTileset|TimeDynamicPointCloud|VoxelPrimitive>} target The entity, array of entities, entity collection, data source, Cesium3DTileset, point cloud, or imagery layer to view. You can also pass a promise that resolves to one of the previously mentioned types.
 * @param {HeadingPitchRange} [offset] The offset from the center of the entity in the local east-north-up reference frame.
 * @returns {Promise<boolean>} A Promise that resolves to true if the zoom was successful or false if the target is not currently visualized in the scene or the zoom was cancelled.
 */
Viewer.prototype.zoomTo = function (target, offset) {
  const options = {
    offset: offset,
  }
  return zoomToOrFly(this, target, options, false)
}

/**
 * Flies the camera to the provided entity, entities, or data source.
 * If the data source is still in the process of loading or the visualization is otherwise still loading,
 * this method waits for the data to be ready before performing the flight.
 *
 * <p>The offset is heading/pitch/range in the local east-north-up reference frame centered at the center of the bounding sphere.
 * The heading and the pitch angles are defined in the local east-north-up reference frame.
 * The heading is the angle from y axis and increasing towards the x axis. Pitch is the rotation from the xy-plane. Positive pitch
 * angles are above the plane. Negative pitch angles are below the plane. The range is the distance from the center. If the range is
 * zero, a range will be computed such that the whole bounding sphere is visible.</p>
 *
 * <p>In 2D, there must be a top down view. The camera will be placed above the target looking down. The height above the
 * target will be the range. The heading will be determined from the offset. If the heading cannot be
 * determined from the offset, the heading will be north.</p>
 *
 * @param {Entity|Entity[]|EntityCollection|DataSource|ImageryLayer|Cesium3DTileset|TimeDynamicPointCloud|Promise<Entity|Entity[]|EntityCollection|DataSource|ImageryLayer|Cesium3DTileset|TimeDynamicPointCloud|VoxelPrimitive>} target The entity, array of entities, entity collection, data source, Cesium3DTileset, point cloud, or imagery layer to view. You can also pass a promise that resolves to one of the previously mentioned types.
 * @param {object} [options] Object with the following properties:
 * @param {number} [options.duration=3.0] The duration of the flight in seconds.
 * @param {number} [options.maximumHeight] The maximum height at the peak of the flight.
 * @param {HeadingPitchRange} [options.offset] The offset from the target in the local east-north-up reference frame centered at the target.
 * @returns {Promise<boolean>} A Promise that resolves to true if the flight was successful or false if the target is not currently visualized in the scene or the flight was cancelled. //TODO: Cleanup entity mentions
 */
Viewer.prototype.flyTo = function (target, options) {
  return zoomToOrFly(this, target, options, true)
}

function zoomToOrFly(that, zoomTarget, options, isFlight) {
  //>>includeStart('debug', pragmas.debug);
  if (!defined(zoomTarget)) {
    throw new DeveloperError('zoomTarget is required.')
  }
  //>>includeEnd('debug');

  cancelZoom(that)

  //We can't actually perform the zoom until all visualization is ready and
  //bounding spheres have been computed.  Therefore we create and return
  //a deferred which will be resolved as part of the post-render step in the
  //frame that actually performs the zoom.
  const zoomPromise = new Promise((resolve) => {
    that._completeZoom = function (value) {
      resolve(value)
    }
  })
  that._zoomPromise = zoomPromise
  that._zoomIsFlight = isFlight
  that._zoomOptions = options

  Promise.resolve(zoomTarget).then(function (zoomTarget) {
    //Only perform the zoom if it wasn't cancelled before the promise resolved.
    if (that._zoomPromise !== zoomPromise) {
      return
    }

    //If the zoom target is a rectangular imagery in an ImageLayer
    if (zoomTarget instanceof ImageryLayer) {
      let rectanglePromise

      if (defined(zoomTarget.imageryProvider)) {
        rectanglePromise = Promise.resolve(zoomTarget.getImageryRectangle())
      } else {
        rectanglePromise = new Promise((resolve) => {
          const removeListener = zoomTarget.readyEvent.addEventListener(() => {
            removeListener()
            resolve(zoomTarget.getImageryRectangle())
          })
        })
      }
      rectanglePromise
        .then(function (rectangle) {
          return computeFlyToLocationForRectangle(rectangle, that.scene)
        })
        .then(function (position) {
          //Only perform the zoom if it wasn't cancelled before the promise was resolved
          if (that._zoomPromise === zoomPromise) {
            that._zoomTarget = position
          }
        })
      return
    }

    if (
      zoomTarget instanceof Cesium3DTileset ||
      zoomTarget instanceof TimeDynamicPointCloud ||
      zoomTarget instanceof VoxelPrimitive
    ) {
      that._zoomTarget = zoomTarget
      return
    }

    //If the zoom target is a data source, and it's in the middle of loading, wait for it to finish loading.
    if (zoomTarget.isLoading && defined(zoomTarget.loadingEvent)) {
      const removeEvent = zoomTarget.loadingEvent.addEventListener(function () {
        removeEvent()

        //Only perform the zoom if it wasn't cancelled before the data source finished.
        if (that._zoomPromise === zoomPromise) {
          that._zoomTarget = zoomTarget.entities.values.slice(0)
        }
      })
      return
    }

    //Zoom target is already an array, just copy it and return.
    if (Array.isArray(zoomTarget)) {
      that._zoomTarget = zoomTarget.slice(0)
      return
    }

    //If zoomTarget is an EntityCollection, this will retrieve the array
    zoomTarget = defaultValue(zoomTarget.values, zoomTarget)

    //If zoomTarget is a DataSource, this will retrieve the array.
    if (defined(zoomTarget.entities)) {
      zoomTarget = zoomTarget.entities.values
    }

    //Zoom target is already an array, just copy it and return.
    if (Array.isArray(zoomTarget)) {
      that._zoomTarget = zoomTarget.slice(0)
    } else {
      //Single entity
      that._zoomTarget = [zoomTarget]
    }
  })

  that.scene.requestRender()
  return zoomPromise
}

function clearZoom(viewer) {
  viewer._zoomPromise = undefined
  viewer._zoomTarget = undefined
  viewer._zoomOptions = undefined
}

function cancelZoom(viewer) {
  const zoomPromise = viewer._zoomPromise
  if (defined(zoomPromise)) {
    clearZoom(viewer)
    viewer._completeZoom(false)
  }
}

/**
 * @private
 */
Viewer.prototype._postRender = function () {
  updateZoomTarget(this)
  updateTrackedEntity(this)
}
function updateZoomTarget(viewer) {
  const target = viewer._zoomTarget
  if (!defined(target) || viewer.scene.mode === SceneMode.MORPHING) {
    return
  }

  const scene = viewer.scene
  const camera = scene.camera
  const zoomOptions = defaultValue(viewer._zoomOptions, {})
  let options
  function zoomToBoundingSphere(boundingSphere) {
    // If offset was originally undefined then give it base value instead of empty object
    if (!defined(zoomOptions.offset)) {
      zoomOptions.offset = new HeadingPitchRange(
        0.0,
        -0.5,
        boundingSphere.radius
      )
    }

    options = {
      offset: zoomOptions.offset,
      duration: zoomOptions.duration,
      maximumHeight: zoomOptions.maximumHeight,
      complete: function () {
        viewer._completeZoom(true)
      },
      cancel: function () {
        viewer._completeZoom(false)
      },
    }

    if (viewer._zoomIsFlight) {
      camera.flyToBoundingSphere(target.boundingSphere, options)
    } else {
      camera.viewBoundingSphere(boundingSphere, zoomOptions.offset)
      camera.lookAtTransform(Matrix4.IDENTITY)

      // Finish the promise
      viewer._completeZoom(true)
    }

    clearZoom(viewer)
  }

  if (target instanceof TimeDynamicPointCloud) {
    if (defined(target.boundingSphere)) {
      zoomToBoundingSphere(target.boundingSphere)
      return
    }

    // Otherwise, the first "frame" needs to have been rendered
    const removeEventListener = target.frameChanged.addEventListener(function (
      timeDynamicPointCloud
    ) {
      zoomToBoundingSphere(timeDynamicPointCloud.boundingSphere)
      removeEventListener()
    })
    return
  }

  if (target instanceof Cesium3DTileset || target instanceof VoxelPrimitive) {
    zoomToBoundingSphere(target.boundingSphere)
    return
  }

  // If zoomTarget was an ImageryLayer
  if (target instanceof Cartographic) {
    options = {
      destination:
        scene.mapProjection.ellipsoid.cartographicToCartesian(target),
      duration: zoomOptions.duration,
      maximumHeight: zoomOptions.maximumHeight,
      complete: function () {
        viewer._completeZoom(true)
      },
      cancel: function () {
        viewer._completeZoom(false)
      },
    }

    if (viewer._zoomIsFlight) {
      camera.flyTo(options)
    } else {
      camera.setView(options)
      viewer._completeZoom(true)
    }
    clearZoom(viewer)
    return
  }

  const entities = target

  const boundingSpheres = []
  for (let i = 0, len = entities.length; i < len; i++) {
    const state = viewer._dataSourceDisplay.getBoundingSphere(
      entities[i],
      false,
      boundingSphereScratch
    )

    if (state === BoundingSphereState.PENDING) {
      return
    } else if (state !== BoundingSphereState.FAILED) {
      boundingSpheres.push(BoundingSphere.clone(boundingSphereScratch))
    }
  }

  if (boundingSpheres.length === 0) {
    cancelZoom(viewer)
    return
  }

  //Stop tracking the current entity.
  viewer.trackedEntity = undefined

  const boundingSphere = BoundingSphere.fromBoundingSpheres(boundingSpheres)

  if (!viewer._zoomIsFlight) {
    camera.viewBoundingSphere(boundingSphere, zoomOptions.offset)
    camera.lookAtTransform(Matrix4.IDENTITY)
    clearZoom(viewer)
    viewer._completeZoom(true)
  } else {
    clearZoom(viewer)
    camera.flyToBoundingSphere(boundingSphere, {
      duration: zoomOptions.duration,
      maximumHeight: zoomOptions.maximumHeight,
      complete: function () {
        viewer._completeZoom(true)
      },
      cancel: function () {
        viewer._completeZoom(false)
      },
      offset: zoomOptions.offset,
    })
  }
}

function updateTrackedEntity(viewer) {
  if (!viewer._needTrackedEntityUpdate) {
    return
  }

  const trackedEntity = viewer._trackedEntity
  const currentTime = viewer.clock.currentTime

  //Verify we have a current position at this time. This is only triggered if a position
  //has become undefined after trackedEntity is set but before the boundingSphere has been
  //computed. In this case, we will track the entity once it comes back into existence.
  const currentPosition = Property.getValueOrUndefined(
    trackedEntity.position,
    currentTime
  )

  if (!defined(currentPosition)) {
    return
  }

  const scene = viewer.scene

  const state = viewer._dataSourceDisplay.getBoundingSphere(
    trackedEntity,
    false,
    boundingSphereScratch
  )
  if (state === BoundingSphereState.PENDING) {
    return
  }

  const sceneMode = scene.mode
  if (
    sceneMode === SceneMode.COLUMBUS_VIEW ||
    sceneMode === SceneMode.SCENE2D
  ) {
    scene.screenSpaceCameraController.enableTranslate = false
  }

  if (
    sceneMode === SceneMode.COLUMBUS_VIEW ||
    sceneMode === SceneMode.SCENE3D
  ) {
    scene.screenSpaceCameraController.enableTilt = false
  }

  const bs =
    state !== BoundingSphereState.FAILED ? boundingSphereScratch : undefined
  viewer._entityView = new EntityView(
    trackedEntity,
    scene,
    scene.mapProjection.ellipsoid
  )
  viewer._entityView.update(currentTime, bs)
  viewer._needTrackedEntityUpdate = false
}

/**
 * A function that augments a Viewer instance with additional functionality.
 * @callback Viewer.ViewerMixin
 * @param {Viewer} viewer The viewer instance.
 * @param {object} options Options object to be passed to the mixin function.
 *
 * @see Viewer#extend
 */
export default Viewer