source: trunk/eraser/Eraser.Util/ExtensionClasses/SplitButton.cs @ 2067

/* 
 * $Id$
 * Copyright 2008-2010 The Eraser Project
 * Original Author: Joel Low <lowjoel@users.sourceforge.net>
 * Modified By:
 * 
 * This file is part of Eraser.
 * 
 * Eraser is free software: you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 * 
 * Eraser is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 * 
 * A copy of the GNU General Public License can be found at
 * <http://www.gnu.org/licenses/>.
 */

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Eraser.Util;
using System.Drawing;

namespace System.Windows.Forms
{
    public class SplitButton : Button
    {
        /// <summary>
        /// Constructor.
        /// </summary>
        public SplitButton()
        {
            FlatStyle = FlatStyle.System;
        }

        protected override CreateParams CreateParams
        {
            get
            {
                CreateParams createParams = base.CreateParams;
                createParams.Style |= NativeMethods.BS_SPLITBUTTON;
                return createParams;
            }
        }

        protected override void WndProc(ref Message m)
        {
            switch ((uint)m.Msg)
            {
                case 0x2000 | NativeMethods.WM_NOTIFY:
                    //Reflected WM_NOTIFY from parent. Check that the handle is ours
                    if (m.HWnd == Handle)
                    {
                        //Then check the code of the message
                        NativeMethods.NMHDR nmHdr = (NativeMethods.NMHDR)
                            m.GetLParam(typeof(NativeMethods.NMHDR));

                        //Handle only BCN_DROPDOWN messages
                        if (nmHdr.code == NativeMethods.BCN_DROPDOWN)
                        {
                            //The dropdown portion of the button is being pressed, show the menu
                            if (ContextMenuStrip != null)
                            {
                                Point point = new Point(Width - ContextMenuStrip.Width, Height);
                                ContextMenuStrip.Show(this, point, ToolStripDropDownDirection.BelowRight);
                                ContextMenuStrip.Closed += OnMenuClosed;
                            }
                        }
                    }
                    break;

                case NativeMethods.WM_PAINT:
                    //Paint the control to have the dropdown portion as pressed when the
                    //menu is shown.
                    DropDownState = ContextMenuStrip != null && ContextMenuStrip.Visible;
                    break;

                case NativeMethods.WM_CONTEXTMENU:
                    //Swallow all context menu clicks on Vista and later -- otherwise
                    //we will also show the context menu when the user right-clicks
                    //the button.
                    if (Environment.OSVersion.Version.Major >= 6)
                        return;
                    break;
            }

            base.WndProc(ref m);
        }

        private bool DropDownState
        {
            set
            {
                NativeMethods.SendMessage(this.Handle, NativeMethods.BCM_SETDROPDOWNSTATE,
                    new UIntPtr(value ? 1U : 0), IntPtr.Zero);
            }
        }

        private void OnMenuClosed(object sender, EventArgs e)
        {
            DropDownState = false;
            ContextMenuStrip.Closed -= OnMenuClosed;
        }
    }
}