XrAnchors#available (#5879)

src/framework/xr/xr-anchors.js

@@ -26,12 +26,24 @@ import { XrAnchor } from './xr-anchor.js';
  * @category XR
  */
 class XrAnchors extends EventHandler {
+    /**
+     * @type {import('./xr-manager.js').XrManager}
+     * @ignore
+     */
+    manager;
+
     /**
      * @type {boolean}
      * @private
      */
     _supported = platform.browser && !!window.XRAnchor;
 
+    /**
+     * @type {boolean}
+     * @private
+     */
+    _available = false;
+
     /**
      * @type {boolean}
      * @private
@@ -87,10 +99,23 @@ class XrAnchors extends EventHandler {
         this.manager = manager;
 
         if (this._supported) {
+            this.manager.on('start', this._onSessionStart, this);
             this.manager.on('end', this._onSessionEnd, this);
         }
     }
 
+    /**
+     * Fired when anchors becomes available.
+     *
+     * @event XrAnchors#available
+     */
+
+    /**
+     * Fired when anchors becomes unavailable.
+     *
+     * @event XrAnchors#unavailable
+     */
+
     /**
      * Fired when anchor failed to be created.
      *
@@ -120,8 +145,19 @@ class XrAnchors extends EventHandler {
      * });
      */
 
+    /** @private */
+    _onSessionStart() {
+        const available = this.manager.session.enabledFeatures.indexOf('anchors') !== -1;
+        if (!available) return;
+        this._available = available;
+        this.fire('available');
+    }
+
     /** @private */
     _onSessionEnd() {
+        if (!this._available) return;
+        this._available = false;
+
         // clear anchor creation queue
         for (let i = 0; i < this._creationQueue.length; i++) {
             if (!this._creationQueue[i].callback)
@@ -140,6 +176,8 @@ class XrAnchors extends EventHandler {
             this._list[i].destroy();
         }
         this._list.length = 0;
+
+        this.fire('unavailable');
     }
 
     /**
@@ -194,6 +232,11 @@ class XrAnchors extends EventHandler {
      * });
      */
     create(position, rotation, callback) {
+        if (!this._available) {
+            callback?.(new Error('Anchors API is not available'), null);
+            return;
+        }
+
         // eslint-disable-next-line no-undef
         if (window.XRHitTestResult && position instanceof XRHitTestResult) {
             const hitResult = position;
@@ -247,6 +290,11 @@ class XrAnchors extends EventHandler {
      * }
      */
     restore(uuid, callback) {
+        if (!this._available) {
+            callback?.(new Error('Anchors API is not available'), null);
+            return;
+        }
+
         if (!this._persistence) {
             callback?.(new Error('Anchor Persistence is not supported'), null);
             return;
@@ -283,6 +331,11 @@ class XrAnchors extends EventHandler {
      * }
      */
     forget(uuid, callback) {
+        if (!this._available) {
+            callback?.(new Error('Anchors API is not available'));
+            return;
+        }
+
         if (!this._persistence) {
             callback?.(new Error('Anchor Persistence is not supported'));
             return;
@@ -308,6 +361,9 @@ class XrAnchors extends EventHandler {
      * @ignore
      */
     update(frame) {
+        if (!this._available)
+            return;
+
         // check if need to create anchors
         if (this._creationQueue.length) {
             for (let i = 0; i < this._creationQueue.length; i++) {
@@ -378,6 +434,15 @@ class XrAnchors extends EventHandler {
         return this._supported;
     }
 
+    /**
+     * True if Anchors are available. This information is available only when session has started.
+     *
+     * @type {boolean}
+     */
+    get available() {
+        return this._available;
+    }
+
     /**
      * True if Anchors support persistence.
      *
@@ -393,6 +458,9 @@ class XrAnchors extends EventHandler {
      * @type {null|string[]}
      */
     get uuids() {
+        if (!this._available)
+            return null;
+
         if (!this._persistence)
             return null;