ZoomEffects.cs

using Gondwana.Physics.Movement.Easing;
using Gondwana.Rendering.Views;
 
namespace Gondwana.Effects;

public abstract class ZoomEffect : DisplayEffect
{
    private float _originalZoom;
    private float _clampedTargetZoom;

    private protected ZoomEffect(float targetZoom, float durationSeconds)
        : base(durationSeconds, EasingKind.Linear)
    {
        if (targetZoom <= 0f)
            throw new ArgumentOutOfRangeException(nameof(targetZoom));
 
        TargetZoom = targetZoom;
    }

    public float TargetZoom { get; }
 
    internal override EffectChannel Channel => EffectChannel.Zoom;
 
    internal override bool SupportsTarget(object target) => target is View;

    private protected override void OnStarting()
    {
        var view = GetTarget<View>();
        _originalZoom = view.Viewport.Zoom;
        _clampedTargetZoom = Math.Clamp(TargetZoom, view.MinZoom, view.MaxZoom);
        view.Viewport.ZoomToOverDuration(_clampedTargetZoom, DurationSeconds);
    }
 
    // View.Update() advances the existing Viewport zoom animator. The effect
    // manager owns only lifecycle, replacement, and completion notification.
    private protected override void ApplyProgress(float progress)
    {
    }

    private protected override void OnCompleted() =>
        GetTarget<View>().Viewport.SnapZoom(_clampedTargetZoom);

    private protected override void RestoreOriginalState() =>
        GetTarget<View>().Viewport.SnapZoom(_originalZoom);
}

public sealed class ZoomInEffect : ZoomEffect
{
    public ZoomInEffect(float targetZoom, float durationSeconds)
        : base(targetZoom, durationSeconds)
    {
    }
}

public sealed class ZoomOutEffect : ZoomEffect
{
    public ZoomOutEffect(float targetZoom, float durationSeconds)
        : base(targetZoom, durationSeconds)
    {
    }
}