[Web] Add feature detection helpers to JS Engine class.

platform/web/js/engine/features.js

@@ -0,0 +1,96 @@
+const Features = { // eslint-disable-line no-unused-vars
+	/**
+	 * Check whether WebGL is available. Optionally, specify a particular version of WebGL to check for.
+	 *
+	 * @param {number=} [majorVersion=1] The major WebGL version to check for.
+	 * @returns {boolean} If the given major version of WebGL is available.
+	 * @function Engine.isWebGLAvailable
+	 */
+	isWebGLAvailable: function (majorVersion = 1) {
+		try {
+			return !!document.createElement('canvas').getContext(['webgl', 'webgl2'][majorVersion - 1]);
+		} catch (e) { /* Not available */ }
+		return false;
+	},
+
+	/**
+	 * Check whether the Fetch API available and supports streaming responses.
+	 *
+	 * @returns {boolean} If the Fetch API is available and supports streaming responses.
+	 * @function Engine.isFetchAvailable
+	 */
+	isFetchAvailable: function () {
+		return 'fetch' in window && 'Response' in window && 'body' in window.Response.prototype;
+	},
+
+	/**
+	 * Check whether the engine is running in a Secure Context.
+	 *
+	 * @returns {boolean} If the engine is running in a Secure Context.
+	 * @function Engine.isSecureContext
+	 */
+	isSecureContext: function () {
+		return window['isSecureContext'] === true;
+	},
+
+	/**
+	 * Check whether the engine is cross origin isolated.
+	 * This value is dependent on Cross-Origin-Opener-Policy and Cross-Origin-Embedder-Policy headers sent by the server.
+	 *
+	 * @returns {boolean} If the engine is running in a Secure Context.
+	 * @function Engine.isSecureContext
+	 */
+	isCrossOriginIsolated: function () {
+		return window['crossOriginIsolated'] === true;
+	},
+
+	/**
+	 * Check whether SharedBufferArray is available.
+	 *
+	 * Most browsers require the page to be running in a secure context, and the
+	 * the server to provide specific CORS headers for SharedArrayBuffer to be available.
+	 *
+	 * @returns {boolean} If SharedArrayBuffer is available.
+	 * @function Engine.isSharedArrayBufferAvailable
+	 */
+	isSharedArrayBufferAvailable: function () {
+		return 'SharedArrayBuffer' in window;
+	},
+
+	/**
+	 * Check whether the AudioContext supports AudioWorkletNodes.
+	 *
+	 * @returns {boolean} If AudioWorkletNode is available.
+	 * @function Engine.isAudioWorkletAvailable
+	 */
+	isAudioWorkletAvailable: function () {
+		return 'AudioContext' in window && 'audioWorklet' in AudioContext.prototype;
+	},
+
+	/**
+	 * Return an array of missing required features (as string).
+	 *
+	 * @returns {Array<string>} A list of human-readable missing features.
+	 * @function Engine.getMissingFeatures
+	 */
+	getMissingFeatures: function () {
+		const missing = [];
+		if (!Features.isWebGLAvailable(2)) {
+			missing.push('WebGL2');
+		}
+		if (!Features.isFetchAvailable()) {
+			missing.push('Fetch');
+		}
+		if (!Features.isSecureContext()) {
+			missing.push('Secure Context');
+		}
+		if (!Features.isCrossOriginIsolated()) {
+			missing.push('Cross Origin Isolation');
+		}
+		if (!Features.isSharedArrayBufferAvailable()) {
+			missing.push('SharedArrayBuffer');
+		}
+		// Audio is normally optional since we have a dummy fallback.
+		return missing;
+	},
+};