Interface: SessionDelegates

Defines callbacks for CloudXR session events.

Applications implement these callbacks to receive notifications about session lifecycle events and WebGL state changes. All callbacks are optional.

Example

const delegates: SessionDelegates = {
  onStreamStarted: () => {
    console.info('CloudXR streaming started');
    // Update UI to show streaming status
  },
  onStreamStopped: (error) => {
    if (error) {
      console.error('Streaming stopped due to error:', error);
    } else {
      console.info('Streaming stopped normally');
    }
  }
};

Properties

onStreamStarted()?

optional onStreamStarted: () => void

Invoked when streaming connects successfully.

Called when the session transitions to the Connected state and streaming is ready to begin. At this point, the session is ready for rendering and all WebGL resources have been initialized.

Returns

void

Example

onStreamStarted: () => {
  console.info('Ready to render CloudXR content');
  // Start your render loop here
}

---

onStreamStopped()?

optional onStreamStopped: (error?) => void

Invoked when streaming stops (either by client or server).

Called when the session stops streaming, either due to a normal disconnection or an error condition. Check the error parameter to determine the reason for the stop.

Parameters

error?

StreamingError

Optional StreamingError if streaming stopped due to an error. If undefined, the stop was intentional (e.g., disconnect() called). Error objects include: - message: User-friendly error description - code: Error code for debugging/reporting (numeric, e.g., 0xC0F2220C) - reasonCode: Stream stop reason code (when available)

Returns

void

Example

onStreamStopped: (error) => {
  if (error) {
    // Display user-friendly message
    console.error('Streaming error:', error.message);

    // Include error code for reporting/debugging (format as hex)
    if (error.code) {
      console.error('Error code: 0x' + error.code.toString(16).toUpperCase());
    }
  } else {
    console.info('Streaming stopped normally');
  }
}

---

onWebGLStateChangeBegin()?

optional onWebGLStateChangeBegin: () => void

Invoked before the session changes any WebGL state.

Called before the session modifies WebGL state during rendering operations. Use this to save the current WebGL state if needed for your application’s rendering pipeline.

Returns

void

Example

onWebGLStateChangeBegin: () => {
  // Save current WebGL state
  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
}

---

onWebGLStateChangeEnd()?

optional onWebGLStateChangeEnd: () => void

Invoked after the session changes any WebGL state.

Called after the session has completed its WebGL state modifications during rendering operations. Use this to restore any WebGL state that your application needs.

Returns

void

Example

onWebGLStateChangeEnd: () => {
  // Restore WebGL state
  gl.bindFramebuffer(gl.FRAMEBUFFER, myFramebuffer);
}

---

onServerMessageReceived()?

optional onServerMessageReceived: (messageData) => void

Invoked when a server message is received through any opaque data channel.

Parameters

messageData

Uint8Array

Raw message data from the server

Returns

void

Deprecated

Use session.availableMessageChannels to get MessageChannel objects and receive messages directly.

Example

onServerMessageReceived: (messageData) => {
  console.log('Received:', new TextDecoder().decode(messageData));
}

---

onMetrics()?

optional onMetrics: (metrics, cadence) => void

Invoked when metrics are produced by the session.

Parameters

metrics

Metrics

Object containing metrics by name

cadence

MetricsCadence

The cadence at which the metrics are presented

Returns

void