Luna UI Documentation

UI Actions are a core feature of the UIView system that allow developers to link custom behaviors to the view's visibility transitions (fade in/out). These actions implement the IUIViewAction interface and are executed automatically whenever the UIView's visibility changes.

The IUIViewAction interface

csharp

namespace CupkekGames.Luna
{
    public interface IUIViewAction
    {
        void OnFadeInStart();
        void OnFadeOut();
    }
}

Member	When it fires
`OnFadeInStart()`	The view starts becoming visible — fade-in begins, the view is born visible via `ApplyStartVisibility(true)`, or the action is added with `activate: true` while the view is already visible.
`OnFadeOut()`	The view finishes hiding — fade-out completes (not when it starts), or the view is born hidden via `ApplyStartVisibility(false)`.

The asymmetry is deliberate: an action registers at fade-in start so its behavior (an Esc handler, a paused timescale) is live while the entrance animation is still playing, and it releases only at fade-out completion so the behavior stays active until the view is actually gone.

Actions also fire through parent-child propagation: when a parent UIView registered via AddChild fades in, the actions of its currently-visible children fire in sync (on parent fade-out, only currently-hidden children get their OnFadeOut re-fired as cleanup — a visible child's actions are released by the child's own fade-out, not the parent's). See Example: Multi Page UI — Nested UIViews for why this matters.

This provides a simple, event-driven way to manage UI behavior that needs to sync with the view's state.

Writing a custom action

Any class implementing the two members can be registered with UIView.AddAction. For example, an action that pauses the game while a menu is open:

csharp

using CupkekGames.Luna;
using UnityEngine;

/// <summary>Pauses gameplay while the owning view is visible.</summary>
public class UIViewActionPauseTime : IUIViewAction
{
    public void OnFadeInStart()
    {
        Time.timeScale = 0f;   // fade-in begins — pause
    }

    public void OnFadeOut()
    {
        Time.timeScale = 1f;   // fade-out finished — resume
    }
}

csharp

myView.WhenUILoaded(() =>
{
    myView.UIView.AddAction(new UIViewActionPauseTime());
});

AddAction(action, activate: true) triggers OnFadeInStart() immediately when the view is already visible at registration time — pass activate: false to defer until the next real fade-in (the nested-views example shows when you need this).

Default Actions

UIViewActionEscape

This class allows you to push and pop a custom action(System.Action) into the InputEscapeManager in sync with the visibility of an UIView. On OnFadeInStart it pushes the callback onto the escape stack under a stable key; on OnFadeOut it pops it again (without executing), so Esc means "your callback" exactly while the view is visible.

Constructor

csharp

public UIViewActionEscape(Action onEscape = null, bool debug = false)

Example

csharp

UIView.AddAction(new UIViewActionEscape(ReturnToPreviousScreen));

See Example: Multi Page UI for more detailed example.