DrawablePaint1.cs

using System;
using System.Diagnostics;
using Eto.Drawing;
using Eto.Forms;

namespace ConsoleApplication22
{
    class MyForm : Form
    {
        public MyForm()
        {
            this.ClientSize = new Eto.Drawing.Size(500, 500);
            this.Title = "Hello, Eto.Forms " + Platform.ID;
            var drawable = new Drawable(false) { Size = new Size(700, 600) };
            int i = 0;
            drawable.Paint += (sender, e) =>
            {
                Debug.Print(DateTime.UtcNow.ToString("yyyy-MM-dd hh:mm:ss.fff") + " Draw #" + ++i + " Rect: " + e.ClipRectangle.ToString());
                var g = e.Graphics;
                g.Clear(Brushes.White);
                for (float y = 10f; y < 390f; y += 1f)
                    g.DrawLine(Colors.Red, new PointF(10f, y), new PointF(390f, y));
            };
            var layout = new PixelLayout();
            layout.Add(drawable, 0, 0);

            Content = layout;
        }
    }

    class Program
    {
        [STAThread]
        static void Main(string[] args)
        {
            new Application(Eto.Platforms.Wpf).Run(new MyForm());
        }
    }
}

DrawablePaint2.cs

using System;
using System.Diagnostics;
using Eto.Drawing;
using Eto.Forms;

namespace ConsoleApplication22
{
    class MyForm : Form
    {
        public MyForm()
        {
            this.ClientSize = new Eto.Drawing.Size(500, 500);
            this.Title = "Hello, Eto.Forms " + Platform.ID;
            var drawable = new Drawable(true) { Size = new Size(700, 600) };
            int i = 0;
            drawable.Paint += (sender, e) =>
            {
                Debug.Print(DateTime.UtcNow.ToString("yyyy-MM-dd hh:mm:ss.fff") + " Draw #" + ++i + " Rect: " + e.ClipRectangle.ToString());
                var g = e.Graphics;
                g.Clear(Brushes.White);
                for (float y = 10f; y < 390f; y += 1f)
                    g.DrawLine(Colors.Red, new PointF(10f, y), new PointF(390f, y));
            };
            var layout = new PixelLayout();
            layout.Add(drawable, 0, 0);

            Content = layout;
        }
    }

    class Program
    {
        [STAThread]
        static void Main(string[] args)
        {
            new Application(Eto.Platforms.Wpf).Run(new MyForm());
        }
    }
}