AutoSizingDialog.cs

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

namespace Eto.Forms
{
  /// <summary>
  /// A dialog that sizes to its content automatically
  /// </summary>
	public class AutoSizingDialog<T> : Dialog<T>
	{
		Panel contentPanel;
		Scrollable scrollable;
		bool isResizing;
		bool hasCustomSize;
		bool hasShown;
		Size? lastContentSize;

		public AutoSizingDialog()
		{
			contentPanel = new Panel();
			contentPanel.SizeChanged += contentPanel_SizeChanged;

			scrollable = new Scrollable
			{
				Border = BorderType.None,
				ExpandContentWidth = false,
				ExpandContentHeight = false,
				Content = contentPanel
			};

			base.Content = scrollable;
		}

		public new Size ClientSize
		{
			get { return contentPanel.Size; }
			set { contentPanel.Size = value; }
		}

		public new Control Content
		{
			get { return contentPanel.Content; }
			set { contentPanel.Content = value; }
		}

		protected override void OnShown(EventArgs e)
		{
			base.OnShown(e);
			hasShown = true;
		}

		protected override void OnSizeChanged(EventArgs e)
		{
			base.OnSizeChanged(e);
			if (hasShown && !isResizing && Resizable)
			{
				// User is changing the size manually, so we keep that size
				hasCustomSize = true;
				scrollable.ExpandContentWidth = true;
				scrollable.ExpandContentHeight = true;
			}

			isResizing = false;
		}

		void contentPanel_SizeChanged(object sender, EventArgs e)
		{
			if (!Loaded || hasCustomSize)
				return;

			var contentSize = scrollable.Content.Size;
			if (contentSize != lastContentSize)
			{
				isResizing = true;
				base.ClientSize = contentSize;
				lastContentSize = contentSize;
			}
		}
	}
}