cirnogodot/Scripts/UI/IntroScenePlayer.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Godot;
using Godot.Collections;

namespace Cirno.Scripts.UI;

public partial class IntroScenePlayer : CanvasLayer
{
    [Export]
    public Control PanelsHolder { get; private set; }
    
    [Export]
    public Array<Texture2D> Images { get; private set; }

    [Export]
    public float TransitionTime = 5f;
    
    [Export]
    public string NextSceneName { get; set; }
    
    private int _currentPanelIndex;
    
    private List<TextureRect> _panels = new ();
    
    public TextureRect CurrentPanel => _panels[_currentPanelIndex];

    private double _timer = 0f;
    
    private bool _running = false;
    
    public override void _Ready()
    {
        _timer = 0;
        _running = true;

        foreach (var image in Images)
        {
            var panel = new TextureRect();
            panel.Texture = image;
            panel.ExpandMode = TextureRect.ExpandModeEnum.KeepSize;
            panel.StretchMode = TextureRect.StretchModeEnum.KeepAspectCentered;
            panel.Visible = false;
            panel.SetModulate(new Color(panel.Modulate.R, panel.Modulate.G, panel.Modulate.B, 0f));
            
            PanelsHolder.CallDeferred("add_child", panel);
            
            _panels.Add(panel);
        }
        
        var first = _panels.First();
        first.Visible = true;
        first.SetModulate(new Color(first.Modulate.R, first.Modulate.G, first.Modulate.B, 1f));
        
    }

    public override void _Process(double delta)
    {
        if (!_running) return;
        
        _timer += delta;   

        if (_timer >= TransitionTime)
        {
            _timer = 0;
            _currentPanelIndex++;

            if (_currentPanelIndex >= _panels.Count)
            {
                _running = false;
                Finished();
                return;
            }

            _running = false;
            
            _ = Transition();
        }
    }

    private void Finished()
    {
        GetTree().ChangeSceneToFile(NextSceneName);
    }

    private async Task Transition()
    {
        TextureRect previousPanel = _panels[_currentPanelIndex-1];

        CurrentPanel.Visible = true;
        
        var tween = GetTree().CreateTween();
        tween.SetEase(Tween.EaseType.InOut);
        tween.SetTrans(Tween.TransitionType.Linear);
        tween.TweenProperty(previousPanel, "modulate:a", 0f, 1f);
        
        tween.TweenProperty(CurrentPanel, "modulate:a", 1f, 1f);
        
        await ToSignal(tween, "finished");

        previousPanel.Visible = false;
        
        _running = true;
    }
}