Commit for development environment setup

PROMS/DropDownPanel_sol/DropDownPanel/Helper/DropDownWindowHelper.cs

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+using System;
+using System.Drawing;
+using System.Runtime.InteropServices;
+using System.Windows.Forms;
+
+namespace AT.STO.UI.Win
+{
+	/// <summary>
+	/// A class to assist in creating popup windows like Combo Box drop-downs and Menus.
+	/// This class includes functionality to keep the title bar of the popup owner form
+	/// active whilst the popup is displayed, and to automatically cancel the popup
+	/// whenever the user clicks outside the popup window or shifts focus to another 
+	/// application.
+	/// 
+	/// Thousand thanks to Steve McMahon:
+	/// http://www.vbaccelerator.com/home/NET/Code/Controls/Popup_Windows/Popup_Windows/Popup_Form_Demonstration.asp
+	/// </summary>
+	internal class DropDownWindowHelper : NativeWindow
+	{
+	#region Private Variable Declarations
+		private EventHandler DropDownClosedHandler = null;
+		
+		private Form					_dropDown			= null;
+		private bool					_dropDownShowing	= false;
+		private DropDownMessageFilter	_filter				= null;
+		private Form					_owner				= null;
+		private bool					_skipClose			= false;
+	#endregion
+	#region Event Declarations
+		public event DropDownCancelEventHandler DropDownCancel;
+		public event DropDownClosedEventHandler DropDownClosed;
+	#endregion
+	#region Constructor / Destructor
+		/// <summary>
+		/// Default constructor.
+		/// </summary>
+		/// <remarks>Use the <see cref="System.Windows.Forms.NativeWindow.AssignHandle"/>
+		/// method to attach this class to the form you want to show popups from.</remarks>
+		public DropDownWindowHelper()
+		{
+			_filter = new DropDownMessageFilter(this);
+			_filter.DropDownCancel += new DropDownCancelEventHandler(Popup_Cancel);
+		}
+	#endregion
+	#region Event Handler
+		private void Popup_Cancel(object sender, DropDownCancelEventArgs e)
+		{
+			OnDropDownCancel(e);
+		}
+
+		/// <summary>
+		/// Responds to the <see cref="System.Windows.Forms.Form.Closed"/>
+		/// event from the popup form.
+		/// </summary>
+		/// <param name="sender">Popup form that has been closed.</param>
+		/// <param name="e">Not used.</param>
+		private void Popup_Closed(object sender, EventArgs e)
+		{
+			CloseDropDown();
+		}
+	
+		/// <summary>
+		/// Subclasses the owning form's existing Window Procedure to enables the 
+		/// title bar to remain active when a popup is show, and to detect if
+		/// the user clicks onto another application whilst the popup is visible.
+		/// </summary>
+		/// <param name="m">Window Procedure Message</param>
+		protected override void WndProc(ref Message m)
+		{
+			base.WndProc(ref m);
+
+			if (DropDownShowing)
+			{
+				if (m.Msg == UIApiCalls.WM_NCACTIVATE)
+				{
+					if (((int)m.WParam) == 0)																// Check if the title bar will made inactive:
+					{	// Note it's no good to try and consume this message; if you try to do that you'll end up with windows
+						UIApiCalls.SendMessage(this.Handle, UIApiCalls.WM_NCACTIVATE, 1, IntPtr.Zero);		// If so reactivate it.
+					}
+				}
+				else if (m.Msg == UIApiCalls.WM_ACTIVATEAPP)
+				{
+					if ((int)m.WParam == 0)																	// Check if the application is being deactivated.
+					{
+						CloseDropDown();																		// It is so cancel the popup:
+						UIApiCalls.PostMessage(this.Handle, UIApiCalls.WM_NCACTIVATE, 0, IntPtr.Zero);		// And put the title bar into the inactive state:
+					}
+				}
+			}
+		}
+	#endregion
+	#region Public Methods
+		/// <summary>
+		/// Shows the specified Form as a popup window, keeping the
+		/// Owner's title bar active and preparing to cancel the popup
+		/// should the user click anywhere outside the popup window.
+		/// <para>Typical code to use this message is as follows:</para>
+		/// <code>
+		///    frmPopup popup = new frmPopup();
+		///    Point location = this.PointToScreen(new Point(button1.Left, button1.Bottom));
+		///    popupHelper.ShowPopup(this, popup, location);
+		/// </code>
+		/// <para>Put as much initialisation code as possible
+		/// into the popup form's constructor, rather than the <see cref="System.Windows.Forms.Load"/>
+		/// event as this will improve visual appearance.</para>
+		/// </summary>
+		/// <param name="Owner">Main form which owns the popup</param>
+		/// <param name="Popup">Window to show as a popup</param>
+		/// <param name="v">Location relative to the screen to show the popup at.</param>
+		public void ShowDropDown(Form Owner, Form DropDown, Point Location)
+		{
+			_owner = Owner;
+			_dropDown = DropDown;
+			Application.AddMessageFilter(_filter);					// Start checking for the popup being cancelled
+			DropDown.StartPosition = FormStartPosition.Manual;		// Set the location of the popup form:
+			DropDown.Location = Location;
+			Owner.AddOwnedForm(DropDown);							// Make it owned by the window that's displaying it:		
+			DropDownClosedHandler = new EventHandler(Popup_Closed);	// Respond to the Closed event in case the popup is closed by its own internal means
+			DropDown.Closed += DropDownClosedHandler;
+
+			_dropDownShowing = true;								// Show the popup:
+			DropDown.Show();
+			DropDown.Activate();
+			
+			// A little bit of fun.  We've shown the popup, but because we've kept the main window's
+			// title bar in focus the tab sequence isn't quite right.  This can be fixed by sending a tab,
+			// but that on its own would shift focus to the second control in the form.  So send a tab,
+			// followed by a reverse-tab.
+			UIApiCalls.keybd_event((byte) Keys.Tab, 0, 0, 0);
+			UIApiCalls.keybd_event((byte) Keys.Tab, 0, UIApiCalls.KEYEVENTF_KEYUP, 0);
+			UIApiCalls.keybd_event((byte) Keys.ShiftKey, 0, 0, 0);
+			UIApiCalls.keybd_event((byte) Keys.Tab, 0, 0, 0);
+			UIApiCalls.keybd_event((byte) Keys.Tab, 0, UIApiCalls.KEYEVENTF_KEYUP, 0);
+			UIApiCalls.keybd_event((byte) Keys.ShiftKey, 0, UIApiCalls.KEYEVENTF_KEYUP, 0);
+
+			_filter.DropDown = DropDown;							// Start filtering for mouse clicks outside the popup	
+		}
+
+		/// <summary>
+		/// Called when the popup is being hidden.
+		/// </summary>
+		public void CloseDropDown()
+		{
+			if (DropDownShowing)
+			{
+				if (!_skipClose)
+				{
+					OnPDropDownClosed(new DropDownClosedEventArgs(_dropDown));						
+				}
+				
+				_skipClose = false;
+
+				_owner.RemoveOwnedForm(_dropDown);					// Make sure the popup is closed and we've cleaned up:
+				_dropDownShowing = false;
+				_dropDown.Closed -= DropDownClosedHandler;
+				DropDownClosedHandler = null;
+				_dropDown.Close();
+
+				Application.RemoveMessageFilter(_filter);			// No longer need to filter for clicks outside the popup.
+
+				// If we did something from the popup which shifted focus to a new form, like showing another popup
+				// or dialog, then Windows won't know how to bring the original owner back to the foreground, so
+				// force it here:
+				_owner.Activate();
+
+				_dropDown = null;									// Null out references for GC
+				_owner = null;				
+			}
+		}
+	#endregion
+	#region Public Properties
+		/// <summary>
+		/// Indicator weither the DropDown is showing.
+		/// </summary>
+		public bool DropDownShowing
+		{
+			get { return _dropDownShowing; }
+		}
+	#endregion
+	#region Event Implementation
+		protected virtual void OnDropDownCancel(DropDownCancelEventArgs e)
+		{
+			if (this.DropDownCancel != null)
+			{
+				this.DropDownCancel(this, e);
+
+				if (!e.Cancel)
+				{
+					_skipClose = true;
+				}
+			}
+		}
+		
+		protected virtual void OnPDropDownClosed(DropDownClosedEventArgs e)
+		{
+		    if (this.DropDownClosed != null)
+		    {
+		        this.DropDownClosed(this, e);
+		    }
+		}
+	#endregion
+	}
+}