Synthesize and send events

Before you synthesize and send custom events, understand how the UI Toolkit event system allocates and sends operating system events.

The event system uses a pool of events to avoid allocating event objects repeatedly. To synthesize and send your own events:

1. Get an event object from the pool of events.
2. Fill in the event properties.
3. Enclose the event in a using block to ensure it’s returned to the event pool.
4. Pass the event to panel.visualTree.SendEvent().

You can send operating system events, such as keyboard and mouse events. To do so, use a UnityEngine.Event to initialize the UI(User Interface) Allows a user to interact with your application. Unity currently supports three UI systems. More info
See in Glossary Toolkit event.

The following example demonstrates how to synthesize and send events:

void SynthesizeAndSendKeyDownEvent(IPanel panel, KeyCode code,
     char character = '\0', EventModifiers modifiers = EventModifiers.None)
{
    // Create a UnityEngine.Event to hold initialization data.
    var evt = new Event() {
        type = EventType.KeyDownEvent,
        keyCode = code,
        character = character,
        modifiers = modifiers
    };

    using (KeyDownEvent keyDownEvent = KeyDownEvent.GetPooled(evt))
    {
        panel.visualTree.SendEvent(keyDownEvent);
    }
}

Note: Don’t send events that don’t come from the operating system and can’t be found in the UnityEngine.Event types. Some events are sent by UI Toolkit as a reaction to internal state changes and must not be sent by external processes. For example, if you send PointerCaptureEvent, visual elements assume that the underlying conditions for that event are met and won’t set pointer capture for them. This might break the internal configurations of the visual elementA node of a visual tree that instantiates or derives from the C# VisualElement class. You can style the look, define the behaviour, and display it on screen as part of the UI. More info
See in Glossary and cause undefined behaviors.

Additional resources

• Dispatch events
• Handle events
• Events reference