WebXR FrameRate

src/framework/xr/xr-manager.js

@@ -265,6 +265,12 @@
      */
     _depthFar = 1000;
 
+    /**
+     * @type {number[]|null}
+     * @private
+     */
+    _supportedFrameRates = null;
+
     /**
      * @type {number}
      * @private
@@ -633,6 +639,30 @@
         });
     }
 
+    /**
+     * Update target frame rate of an XR session to one of supported value provided by
+     * supportedFrameRates list.
+     * 
+     * @param {number} frameRate - Target frame rate. It should be any value from the list
+     * of supportedFrameRates.
+     * @param {Function} [callback] - Callback that will be called when frameRate has been
+     * updated or failed to update with error provided.
+     */
+    updateTargetFrameRate(frameRate, callback) {
+        if (!this._session?.updateTargetFrameRate) {
+            callback?.(new Error('unable to update frameRate'));
+            return;
+        }
+
+        this._session.updateTargetFrameRate(frameRate)
+            .then(() => {
+                callback?.();
+            })
+            .catch((err) => {
+                callback?.(err);
+            });
+    }
+
     /**
      * @param {string} type - Session type.
      * @private
@@ -709,6 +739,16 @@
 
         this._createBaseLayer();
 
+        if (this.session.supportedFrameRates) {
+            this._supportedFrameRates = Array.from(this.session.supportedFrameRates);
+        } else {
+            this._supportedFrameRates = null;
+        }
+
+        this._session.addEventListener('frameratechange', () => {
+            this.fire('frameratechange', this._session?.frameRate);
+        });
+
         // request reference space
         session.requestReferenceSpace(spaceType).then((referenceSpace) => {
             this._referenceSpace = referenceSpace;
@@ -949,6 +989,25 @@
         return this._session;
     }
 
+    /**
+     * XR session frameRate or null if this information is not available. This value can change
+     * during an active XR session.
+     *
+     * @type {number|null}
+     */
+    get frameRate() {
+        return this._session?.frameRate ?? null;
+    }
+
+    /**
+     * List of supported frame rates, or null if this data is not available.
+     *
+     * @type {number[]|null}
+     */
+    get supportedFrameRates() {
+        return this._supportedFrameRates;
+    }
+
     /**
      * Framebuffer scale factor. This value is read-only and can only be set when starting a new
      * XR session.