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Assets/BITKit/Unity/Scripts/UX/Painter/SkiaPainter.cs

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+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net.Sockets.Kcp;
+using SkiaSharp;
+using UnityEngine;
+using UnityEngine.UIElements;
+
+namespace BITKit.UX
+{
+	public class SkiaPainter : VisualElement
+	{
+		public new class UxmlFactory : UxmlFactory<SkiaPainter, UxmlTraits> { }
+		public SkiaPainter()
+		{
+			RegisterCallback<GeometryChangedEvent>(OnGeometryChanged);
+			RegisterCallback<MouseDownEvent>(OnMouseDown);
+			RegisterCallback<MouseUpEvent>(OnMouseUp);
+			RegisterCallback<MouseMoveEvent>(OnMouseMove);
+		}
+		private bool _isPainting;
+		private readonly List<Vector2> _points = new();
+		private SKImageInfo _info;
+		private SKCanvas _canvas;
+		private SKSurface _surface;
+		private Rect _rect;
+		private readonly SKPaint _linePaint = new()
+		{
+			Style = SKPaintStyle.Stroke,
+			Color = SKColors.Red,
+			StrokeWidth = 5
+		};
+		public void ClearCanvas()
+		{
+			_points.Clear();
+			Rebuild();
+		}
+		private void OnMouseMove(MouseMoveEvent evt)
+		{
+			if (_isPainting is false) return;
+			var pos = evt.localMousePosition;
+			pos.y = layout.height - pos.y;
+			if (_rect.Contains(pos) is false)
+			{
+				var last = _points.LastOrDefault();
+				if (last == default) return;
+				_points.Add(default);
+				return;
+			}
+			_points.Add(pos);
+			Rebuild();
+		}
+
+		private void OnMouseUp(MouseUpEvent evt)
+		{
+			_isPainting = false;
+			var last = _points.LastOrDefault();
+			if (last != default)
+				_points.Add(default);
+		}
+
+		private void OnMouseDown(MouseDownEvent evt)
+		{
+			_isPainting = true;
+		}
+		private void OnGeometryChanged(GeometryChangedEvent evt)
+		{
+			if(float.IsNaN(layout.width) || float.IsNaN(layout.height))
+				return;
+			_linePaint.Color = resolvedStyle.color.ToSKColor();
+			_surface?.Dispose();
+			_info = new SKImageInfo((int)layout.width, (int)layout.height);
+			_surface = SKSurface.Create(_info);
+			_canvas = _surface.Canvas;
+			_rect = new Rect(0, 0, layout.width, layout.height);
+			Rebuild();
+		}
+		private void Rebuild()
+		{
+			if (_canvas is null) return;
+			_canvas.Clear();
+			DoubleBuffer<Vector2> buffer = new();
+			foreach (var pos in _points)
+			{
+				if (pos == default)
+				{
+					buffer.Clear();
+				}
+				else
+				{
+					if (buffer.TryGetRelease(out var previousPoint))
+					{
+						_canvas.DrawLine(previousPoint.x, previousPoint.y, pos.x, pos.y, _linePaint);
+					}
+					buffer.Release(pos);
+				}
+			}
+			var texture = _info.ToTexture2D(_surface);
+			style.backgroundImage = texture;
+		}
+		public string Base64 => _surface?.GetBase64();
+	}
+}
+