Vanara/Windows.Forms/Extenders/VistaControlExtender.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Windows.Forms;
using Vanara.Extensions;
using static Vanara.PInvoke.User32;

namespace Vanara.Windows.Forms
{
	/// <summary>Extends standard WinForms controls with post-Vista capabilities.</summary>
	/// <seealso cref="Component"/>
	/// <seealso cref="IExtenderProvider"/>
	[ProvideProperty(ShowShield, typeof(ButtonBase))]
	[ProvideProperty(CueBanner, typeof(ComboBox))]
	[ProvideProperty(MinVisibleItems, typeof(ComboBox))]
	//[ProvideProperty(CueBanner, typeof(TextBox))]
	public sealed class VistaControlExtender : Component, IExtenderProvider, ISupportInitialize
	{
		internal const string CueBanner = "CueBanner";
		internal const string MinVisibleItems = "MinVisibleItems";
		internal const string ShowShield = "ShowShield";

		private readonly Dictionary<Component, Dictionary<string, (object value, Action<Control, object> setter)>> bag = new Dictionary<Component, Dictionary<string, (object value, Action<Control, object> setter)>>();
		private readonly Container components = new Container();

		/// <summary>Initializes a new instance of the <see cref="VistaControlExtender"/> class.</summary>
		public VistaControlExtender() { }

		/// <summary>Initializes a new instance of the <see cref="VistaControlExtender"/> class.</summary>
		/// <param name="container">The container.</param>
		public VistaControlExtender(IContainer container) => container.Add(this);

		private static bool IsMinVista { get; } = Environment.OSVersion.Version.Major >= 6;

		/// <summary>Gets the text that is displayed as a prompt for an unselected <see cref="ComboBox"/>.</summary>
		/// <param name="comboBox">The <see cref="ComboBox"/> instance.</param>
		/// <returns>The cue text to display.</returns>
		[DisplayName(CueBanner), DefaultValue(null), Category("Appearance")]
		[Description("Text that is displayed as a prompt for an unselected ComboBox.")]
		public string GetCueBanner(ComboBox comboBox) => GetValue<string>(comboBox, CueBanner, out _);

		/// <summary>Sets the text that is displayed as a prompt for an unselected <see cref="ComboBox"/>.</summary>
		/// <param name="comboBox">The <see cref="ComboBox"/> instance.</param>
		/// <param name="value">The cue text to display.</param>
		public void SetCueBanner(ComboBox comboBox, string value) => SetValue(comboBox, CueBanner, value, SetCueBannerValue);

		/// <summary>Gets the minimum number of visible items in the drop-down list of a <see cref="ComboBox"/>.</summary>
		/// <param name="comboBox">The <see cref="ComboBox"/> instance.</param>
		/// <returns>The minimum number of visible items in the drop-down list.</returns>
		[DisplayName(MinVisibleItems), DefaultValue(30), Category("Appearance")]
		[Description("The minimum number of visible items in the drop-down list of a combo box.")]
		public int GetMinVisibleItems(ComboBox comboBox) => GetValue(comboBox, MinVisibleItems, out _, comboBox.SendMessage((uint)ComboBoxMessage.CB_SETMINVISIBLE).ToInt32());

		/// <summary>Sets the minimum number of visible items in the drop-down list of a <see cref="ComboBox"/>.</summary>
		/// <param name="comboBox">The <see cref="ComboBox"/> instance.</param>
		/// <param name="value">The minimum number of visible items in the drop-down list.</param>
		public void SetMinVisibleItems(ComboBox comboBox, int value) => SetValue(comboBox, MinVisibleItems, value, SetMinVisibleItemsValue);

		/// <summary>
		/// Gets a value which indicates whether a shield is shown on the button to indicate that elevated permissions are required to
		/// perform the action of the button.
		/// </summary>
		/// <param name="btn">The Button instance.</param>
		/// <returns><see langword="true"/> if the shield should be shown; <see langword="false"/> otherwise.</returns>
		[DisplayName(ShowShield), DefaultValue(false), Category("Appearance")]
		[Description("Indicates whether a shield is shown on the button to indicate that elevated permissions are required to perform the action of the button.")]
		public bool GetShowShield(ButtonBase btn) => GetValue<bool>(btn, ShowShield, out _);

		/// <summary>
		/// Sets a value which indicates whether a shield is shown on the button to indicate that elevated permissions are required to
		/// perform the action of the button.
		/// </summary>
		/// <param name="btn">The Button instance.</param>
		/// <param name="value"><see langword="true"/> if the shield should be shown; <see langword="false"/> otherwise.</param>
		public void SetShowShield(ButtonBase btn, bool value) => SetValue(btn, ShowShield, value, SetShowShieldValue);

		void ISupportInitialize.BeginInit()
		{
		}

		bool IExtenderProvider.CanExtend(object extendee) => extendee is ComboBox || (extendee is ButtonBase && extendee.GetType().GetProperty(ShowShield) is null);

		void ISupportInitialize.EndInit()
		{
			if (!DesignMode)
			{
				foreach (var key in bag.Keys.OfType<Control>())
					key.HandleCreated += OnComponentHandleCreated;
			}
		}

		/// <summary>
		/// Releases the unmanaged resources used by the <see cref="T:System.ComponentModel.Component"/> and optionally releases the managed resources.
		/// </summary>
		/// <param name="disposing">
		/// <see langword="true"/> to release both managed and unmanaged resources; <see langword="false"/> to release only unmanaged resources.
		/// </param>
		protected override void Dispose(bool disposing)
		{
			if (disposing)
			{
				foreach (var key in bag.Keys.OfType<Control>())
					try { key.HandleCreated -= OnComponentHandleCreated; } catch { }
				components?.Dispose();
			}
			base.Dispose(disposing);
		}

		private static void SetCueBannerValue(Control comboBox, object value)
		{
			(comboBox as ComboBox)?.SetCueBanner(value?.ToString());
			comboBox.Invalidate();
		}

		private static void SetMinVisibleItemsValue(Control comboBox, object value)
		{
			if (!IsMinVista) return;
			comboBox.SendMessage((uint)ComboBoxMessage.CB_SETMINVISIBLE, (IntPtr)value);
			comboBox.Invalidate();
		}

		private static void SetShowShieldValue(Control btn, object value)
		{
			(btn as ButtonBase)?.SetElevationRequiredState((bool)value);
			btn.Invalidate();
		}

		/*[DisplayName(CueBanner), DefaultValue(null), Category("Appearance")]
		[Description("Text that is displayed as a prompt for an unselected TextBox.")]
		public string GetCueBanner(TextBox textBox) => GetValue<string>(textBox, CueBanner);

		public void SetCueBanner(TextBox textBox, string value)
		{
			if (SetValue(textBox, CueBanner, value))
				textBox.SetCueBanner(value);
		}*/

		private T GetValue<T>(Control comp, string propName, out Action<Control, object> setter, T defValue = default)
		{
			if (bag.TryGetValue(comp, out var props) && props.TryGetValue(propName, out var value))
			{
				setter = value.setter;
				return (T)value.value;
			}
			setter = null;
			return defValue;
		}

		private void OnComponentHandleCreated(object sender, EventArgs e)
		{
			foreach (var kv in bag.Where(kv => ReferenceEquals(kv.Key, sender)))
				foreach (var (value, setter) in kv.Value.Values)
					setter?.Invoke(sender as Control, value);
		}

		private bool SetValue<T>(Control comp, string propName, T value, Action<Control, object> setter)
		{
			if (Equals(value, GetValue<T>(comp, propName, out _))) return false;
			if (!bag.ContainsKey(comp))
				bag.Add(comp, new Dictionary<string, (object value, Action<Control, object> setter)>());
			bag[comp][propName] = (value, setter);
			return true;
		}
	}
}