# TrickleDown

> Use this enum to specify during which propagation phase the event handler is executed.

## Definition

* **Type:** Enum
* **Namespace:** [UnityEngine.UIElements](/engine/6000.7/script-reference/unityengine/uielements.md)
* **Assembly:** UnityEngine.UIElementsModule

```csharp
public enum TrickleDown
```

## Remarks

Additional Resources: [PropagationPhase](/engine/6000.7/script-reference/unityengine/uielements/propagationphase.md), [CallbackEventHandler.RegisterCallback](/engine/6000.7/script-reference/unityengine/uielements/callbackeventhandler/registercallback.md)

## Fields

| Value                                                                                                | Description                                                                                                                                                                                                      |
| ---------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [NoTrickleDown](/engine/6000.7/script-reference/unityengine/uielements/trickledown/notrickledown.md) | Execute the event handler during the BubbleUp propagation phase if the event bubbles and the element is a parent of the event's target, or if the callback is registered directly on the event's target.         |
| [TrickleDown](/engine/6000.7/script-reference/unityengine/uielements/trickledown/trickledown.md)     | Execute the event handler during the TrickleDown propagation phase if the event tricklesDown and the element is a parent of the event's target, or if the callback is registered directly on the event's target. |