Events

In Diffusion Studio, the Composition emits various events related to playback control, similar to those found in many editing applications:


const composition = new core.Composition();
 
composition.on('currentframe', (event) => {
  // Logs the current frame of the playback
  console.log(event.detail);
});
 
// Logs a CustomEvent when playback starts
composition.on('play', console.log);
 
// Logs a CustomEvent when playback stops
composition.on('pause', console.log);

As with vanilla JavaScript’s CustomEvent, you can access the object that triggered the event using event.currentTarget.

Track Events

A Track automatically bubbles up events from its clips. Instead of subscribing to individual clip events, you can listen for the same events directly on the Track.

In addition to clip events, Tracks also emit attach and detach events when they are added to or removed from a Composition:


track.on('attach', console.log);
track.on('detach', console.log);

Clip Events

Clips represent individual media assets, and you can subscribe to various events that indicate changes or updates:


clip.on('frame', console.log);
clip.on('update', console.log);

These events are triggered when the clip’s position on the timeline changes or when a visual update occurs.

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Tip: If you want to catch all events from a clip, you can subscribe to all events at once using the wildcard: clip.on('*', console.log);

Unsubscribing from Events

The on method returns an event ID, which you can use to unsubscribe from events when they are no longer needed:


const attachEvt = clip.on('attach', console.log);
const detachEvt = clip.on('detach', console.log);
 
clip.off(attachEvt);
clip.off(detachEvt);

Waiting for Events

Diffusion Studio provides a convenient way to wait for specific events to occur, which is particularly useful in asynchronous workflows:


await new Promise(clip.resolve('load'));

This code will pause execution until the load event is triggered, ensuring that the clip has been fully loaded before proceeding.