SKControl.cs

using System;
using System.ComponentModel;
using System.Drawing;
using System.Drawing.Imaging;
using System.Windows.Forms;

namespace SkiaSharp.Views.Desktop
{
	[DefaultEvent("PaintSurface")]
	[DefaultProperty("Name")]
	public class SKControl : Control
	{
		private readonly bool designMode;

		private Bitmap bitmap;

		public SKControl()
		{
			DoubleBuffered = true;
			SetStyle(ControlStyles.ResizeRedraw, true);

			designMode = DesignMode || LicenseManager.UsageMode == LicenseUsageMode.Designtime;
		}

		[Bindable(false)]
		[Browsable(false)]
		[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
		[EditorBrowsable(EditorBrowsableState.Never)]
		public SKSize CanvasSize => bitmap == null ? SKSize.Empty : new SKSize(bitmap.Width, bitmap.Height);

		[Category("Appearance")]
		public event EventHandler<SKPaintSurfaceEventArgs> PaintSurface;

		private bool painting = false;

		protected override void OnPaint(PaintEventArgs e)
		{
			if (designMode)
				return;

			if (painting) return;

			painting = true;

			base.OnPaint(e);

			// get the bitmap
			CreateBitmap();

			var data = bitmap.LockBits(new Rectangle(0, 0, Width, Height), ImageLockMode.WriteOnly, bitmap.PixelFormat);

			// create the surface
			var info = new SKImageInfo(Width, Height, SKImageInfo.PlatformColorType, SKAlphaType.Premul);
			using (var surface = SKSurface.Create(info, data.Scan0, data.Stride))
			{
				// start drawing
				OnPaintSurface(new SKPaintSurfaceEventArgs(surface, info));

				surface.Canvas.Flush();
			}

			// write the bitmap to the graphics
			bitmap.UnlockBits(data);
			e.Graphics.DrawImage(bitmap, 0, 0);

			painting = false;
		}

		protected virtual void OnPaintSurface(SKPaintSurfaceEventArgs e)
		{
			// invoke the event
			PaintSurface?.Invoke(this, e);
		}
		
		protected override void Dispose(bool disposing)
		{
			base.Dispose(disposing);

			FreeBitmap();
		}

		private void CreateBitmap()
		{
			if (bitmap == null || bitmap.Width != Width || bitmap.Height != Height)
			{
				FreeBitmap();

				bitmap = new Bitmap(Width, Height, PixelFormat.Format32bppPArgb);
			}
		}

		private void FreeBitmap()
		{
			if (bitmap != null)
			{
				bitmap.Dispose();
				bitmap = null;
			}
		}
	}
}