GSS2Rework/GSS2.UI.Core/SectionPanel.cs

using Avalonia;
using Avalonia.Controls;
using Avalonia.Media;

namespace GSS2.UI.Core;

public enum SectionDirection
{
    UpDown,
    DownUp,
    LeftRight,
    RightLeft
}

public class SectionPanel : Panel
{
    public static readonly StyledProperty<int> CurrentIndexProperty = AvaloniaProperty.Register<SectionPanel, int>(nameof(CurrentIndex), 0);
    public int CurrentIndex
    {
        get => GetValue(CurrentIndexProperty);
        set => SetValue(CurrentIndexProperty, value);
    }
    public static readonly StyledProperty<double> AnimationSpeedProperty = AvaloniaProperty.Register<SectionPanel, double>(nameof(AnimationSpeed), 300);
    public double AnimationSpeed
    {
        get => GetValue(AnimationSpeedProperty);
        set => SetValue(AnimationSpeedProperty, value);
    }
    public static readonly StyledProperty<SectionDirection> DirectionProperty = AvaloniaProperty.Register<SectionPanel, SectionDirection>(nameof(Direction), SectionDirection.UpDown);
    public SectionDirection Direction
    {
        get => GetValue(DirectionProperty);
        set => SetValue(DirectionProperty, value);
    }

    public SectionPanel()
    : base()
    {
        CurrentIndexProperty.Changed.AddClassHandler<SectionPanel>((panel, _) => panel.InvalidateArrange());
    }

    protected override Size MeasureOverride(Size availableSize)
    {
        foreach (var child in Children)
            child.Measure(availableSize);

        Console.WriteLine(availableSize);
        return availableSize;
    }
    protected override Size ArrangeOverride(Size finalSize)
    {
        for (int i = 0; i < Children.Count; i++)
        {
            var child = Children[i];

            var rect = Direction switch
            {
                SectionDirection.UpDown => new Rect(0, i * finalSize.Height, finalSize.Width, finalSize.Height),
                SectionDirection.DownUp => new Rect(0, -i * finalSize.Height, finalSize.Width, finalSize.Height),
                SectionDirection.LeftRight => new Rect(i * finalSize.Width, 0, finalSize.Width, finalSize.Height),
                SectionDirection.RightLeft => new Rect(-i * finalSize.Width, 0, finalSize.Width, finalSize.Height),

                _ => default
            };

            child.Arrange(rect);
        }

        ApplyOffset(finalSize);

        return finalSize;
    }
    private void ApplyOffset(Size size)
    {
        double offset = Direction switch
        {
            SectionDirection.UpDown => -CurrentIndex * size.Height,
            SectionDirection.DownUp => CurrentIndex * size.Height,
            SectionDirection.LeftRight => -CurrentIndex * size.Width,
            SectionDirection.RightLeft => CurrentIndex * size.Width,
            _ => 0
        };

        var transform = RenderTransform as TranslateTransform;
        if (transform is null)
        {
            transform = new TranslateTransform();
            RenderTransform = transform;
        }

        if (Direction is SectionDirection.LeftRight or SectionDirection.RightLeft)
            transform.X = offset;
        else
            transform.Y = offset;
    }
}