UIScrollbar.cs

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using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using ReLogic.Content;
using Terraria.Audio;
using Terraria.UI;
 
namespace Terraria.GameContent.UI.Elements;
 
public class UIScrollbar : UIElement
{
    private float _viewPosition;
 
    private float _viewSize = 1f;
 
    private float _maxViewSize = 20f;
 
    private bool _isDragging;
 
    private bool _isHoveringOverHandle;
 
    private float _dragYOffset;
 
    private Asset<Texture2D> _texture;
 
    private Asset<Texture2D> _innerTexture;
 
    public float ViewPosition
    {
        get
        {
            return _viewPosition;
        }
        set
        {
            _viewPosition = MathHelper.Clamp(value, 0f, _maxViewSize - _viewSize);
        }
    }
 
    public bool CanScroll => _maxViewSize != _viewSize;
 
    public void GoToBottom()
    {
        ViewPosition = _maxViewSize - _viewSize;
    }
 
    public UIScrollbar()
    {
        Width.Set(20f, 0f);
        MaxWidth.Set(20f, 0f);
        _texture = Main.Assets.Request<Texture2D>("Images/UI/Scrollbar", (AssetRequestMode)1);
        _innerTexture = Main.Assets.Request<Texture2D>("Images/UI/ScrollbarInner", (AssetRequestMode)1);
        PaddingTop = 5f;
        PaddingBottom = 5f;
    }
 
    public void SetView(float viewSize, float maxViewSize)
    {
        viewSize = MathHelper.Clamp(viewSize, 0f, maxViewSize);
        _viewPosition = MathHelper.Clamp(_viewPosition, 0f, maxViewSize - viewSize);
        _viewSize = viewSize;
        _maxViewSize = maxViewSize;
    }
 
    public float GetValue()
    {
        return _viewPosition;
    }
 
    private Rectangle GetHandleRectangle()
    {
        CalculatedStyle innerDimensions = GetInnerDimensions();
        if (_maxViewSize == 0f && _viewSize == 0f)
        {
            _viewSize = 1f;
            _maxViewSize = 1f;
        }
        return new Rectangle((int)innerDimensions.X, (int)(innerDimensions.Y + innerDimensions.Height * (_viewPosition / _maxViewSize)) - 3, 20, (int)(innerDimensions.Height * (_viewSize / _maxViewSize)) + 7);
    }
 
    private void DrawBar(SpriteBatch spriteBatch, Texture2D texture, Rectangle dimensions, Color color)
    {
        spriteBatch.Draw(texture, new Rectangle(dimensions.X, dimensions.Y - 6, dimensions.Width, 6), new Rectangle(0, 0, texture.Width, 6), color);
        spriteBatch.Draw(texture, new Rectangle(dimensions.X, dimensions.Y, dimensions.Width, dimensions.Height), new Rectangle(0, 6, texture.Width, 4), color);
        spriteBatch.Draw(texture, new Rectangle(dimensions.X, dimensions.Y + dimensions.Height, dimensions.Width, 6), new Rectangle(0, texture.Height - 6, texture.Width, 6), color);
    }
 
    protected override void DrawSelf(SpriteBatch spriteBatch)
    {
        CalculatedStyle dimensions = GetDimensions();
        CalculatedStyle innerDimensions = GetInnerDimensions();
        if (_isDragging)
        {
            float num = UserInterface.ActiveInstance.MousePosition.Y - innerDimensions.Y - _dragYOffset;
            _viewPosition = MathHelper.Clamp(num / innerDimensions.Height * _maxViewSize, 0f, _maxViewSize - _viewSize);
        }
        Rectangle handleRectangle = GetHandleRectangle();
        Vector2 mousePosition = UserInterface.ActiveInstance.MousePosition;
        bool isHoveringOverHandle = _isHoveringOverHandle;
        _isHoveringOverHandle = handleRectangle.Contains(new Point((int)mousePosition.X, (int)mousePosition.Y));
        if (!isHoveringOverHandle && _isHoveringOverHandle && Main.hasFocus)
        {
            SoundEngine.PlaySound(12);
        }
        DrawBar(spriteBatch, _texture.Value, dimensions.ToRectangle(), Color.White);
        DrawBar(spriteBatch, _innerTexture.Value, handleRectangle, Color.White * ((_isDragging || _isHoveringOverHandle) ? 1f : 0.85f));
    }
 
    public override void LeftMouseDown(UIMouseEvent evt)
    {
        base.LeftMouseDown(evt);
        if (evt.Target == this)
        {
            Rectangle handleRectangle = GetHandleRectangle();
            if (handleRectangle.Contains(new Point((int)evt.MousePosition.X, (int)evt.MousePosition.Y)))
            {
                _isDragging = true;
                _dragYOffset = evt.MousePosition.Y - (float)handleRectangle.Y;
            }
            else
            {
                CalculatedStyle innerDimensions = GetInnerDimensions();
                float num = UserInterface.ActiveInstance.MousePosition.Y - innerDimensions.Y - (float)(handleRectangle.Height >> 1);
                _viewPosition = MathHelper.Clamp(num / innerDimensions.Height * _maxViewSize, 0f, _maxViewSize - _viewSize);
            }
        }
    }
 
    public override void LeftMouseUp(UIMouseEvent evt)
    {
        base.LeftMouseUp(evt);
        _isDragging = false;
    }
}