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111 lines
3.6 KiB
JavaScript
111 lines
3.6 KiB
JavaScript
import defined from "../Core/defined.js";
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import DeveloperError from "../Core/DeveloperError.js";
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import Event from "../Core/Event.js";
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/**
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* A {@link Property} whose value is lazily evaluated by a callback function.
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*
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* @alias CallbackProperty
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* @constructor
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*
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* @param {CallbackProperty.Callback} callback The function to be called when the property is evaluated.
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* @param {Boolean} isConstant <code>true</code> when the callback function returns the same value every time, <code>false</code> if the value will change.
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*/
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function CallbackProperty(callback, isConstant) {
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this._callback = undefined;
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this._isConstant = undefined;
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this._definitionChanged = new Event();
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this.setCallback(callback, isConstant);
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}
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Object.defineProperties(CallbackProperty.prototype, {
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/**
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* Gets a value indicating if this property is constant.
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* @memberof CallbackProperty.prototype
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*
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* @type {Boolean}
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* @readonly
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*/
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isConstant: {
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get: function () {
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return this._isConstant;
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},
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},
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/**
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* Gets the event that is raised whenever the definition of this property changes.
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* The definition is changed whenever setCallback is called.
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* @memberof CallbackProperty.prototype
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*
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* @type {Event}
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* @readonly
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*/
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definitionChanged: {
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get: function () {
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return this._definitionChanged;
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},
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},
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});
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/**
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* Gets the value of the property.
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*
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* @param {JulianDate} [time] The time for which to retrieve the value. This parameter is unused since the value does not change with respect to time.
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* @param {Object} [result] The object to store the value into, if omitted, a new instance is created and returned.
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* @returns {Object} The modified result parameter or a new instance if the result parameter was not supplied or is unsupported.
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*/
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CallbackProperty.prototype.getValue = function (time, result) {
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return this._callback(time, result);
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};
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/**
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* Sets the callback to be used.
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*
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* @param {CallbackProperty.Callback} callback The function to be called when the property is evaluated.
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* @param {Boolean} isConstant <code>true</code> when the callback function returns the same value every time, <code>false</code> if the value will change.
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*/
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CallbackProperty.prototype.setCallback = function (callback, isConstant) {
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//>>includeStart('debug', pragmas.debug);
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if (!defined(callback)) {
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throw new DeveloperError("callback is required.");
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}
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if (!defined(isConstant)) {
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throw new DeveloperError("isConstant is required.");
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}
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//>>includeEnd('debug');
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var changed = this._callback !== callback || this._isConstant !== isConstant;
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this._callback = callback;
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this._isConstant = isConstant;
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if (changed) {
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this._definitionChanged.raiseEvent(this);
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}
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};
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/**
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* Compares this property to the provided property and returns
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* <code>true</code> if they are equal, <code>false</code> otherwise.
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*
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* @param {Property} [other] The other property.
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* @returns {Boolean} <code>true</code> if left and right are equal, <code>false</code> otherwise.
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*/
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CallbackProperty.prototype.equals = function (other) {
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return (
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this === other ||
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(other instanceof CallbackProperty &&
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this._callback === other._callback &&
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this._isConstant === other._isConstant)
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);
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};
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/**
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* A function that returns the value of the property.
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* @callback CallbackProperty.Callback
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*
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* @param {JulianDate} [time] The time for which to retrieve the value.
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* @param {Object} [result] The object to store the value into, if omitted, a new instance is created and returned.
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* @returns {Object} The modified result parameter or a new instance if the result parameter was not supplied or is unsupported.
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*/
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export default CallbackProperty;
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