using System;
using System.Text;
using System.Drawing;
using System.Windows.Forms;
using System.Runtime.InteropServices;
namespace TradeIdeas.TIProGUI
{
    public class CenterWinDialog : IDisposable
    {
        private int _mTries = 0;
        private readonly Form _mOwner;

        public CenterWinDialog(Form owner)
        {
            _mOwner = owner;
            owner.BeginInvoke(new MethodInvoker(FindDialog));
        }

        private void FindDialog()
        {
            // Enumerate windows to find the message box
            if (_mTries < 0) return;
            EnumThreadWndProc callback = new EnumThreadWndProc(CheckWindow);
            if (EnumThreadWindows(GetCurrentThreadId(), callback, IntPtr.Zero))
            {
                if (++_mTries < 10) _mOwner.BeginInvoke(new MethodInvoker(FindDialog));
            }
        }
        private bool CheckWindow(IntPtr hWnd, IntPtr lp)
        {
            // Checks if <hWnd> is a dialog
            StringBuilder sb = new StringBuilder(260);
            GetClassName(hWnd, sb, sb.Capacity);
            if (sb.ToString() != "#32770") return true;
            // Got it
            Rectangle frmRect = new Rectangle(_mOwner.Location, _mOwner.Size);
            Rect dlgRect;
            GetWindowRect(hWnd, out dlgRect);
            MoveWindow(hWnd,
                frmRect.Left + (frmRect.Width - dlgRect.Right + dlgRect.Left) / 2,
                frmRect.Top + (frmRect.Height - dlgRect.Bottom + dlgRect.Top) / 2,
                dlgRect.Right - dlgRect.Left,
                dlgRect.Bottom - dlgRect.Top, true);
            return false;
        }
        public void Dispose()
        {
            _mTries = -1;
        }

        // P/Invoke declarations
        private delegate bool EnumThreadWndProc(IntPtr hWnd, IntPtr lp);
        [DllImport("user32.dll")]
        private static extern bool EnumThreadWindows(int tid, EnumThreadWndProc callback, IntPtr lp);
        [DllImport("kernel32.dll")]
        private static extern int GetCurrentThreadId();
        [DllImport("user32.dll")]
        private static extern int GetClassName(IntPtr hWnd, StringBuilder buffer, int buflen);
        [DllImport("user32.dll")]
        private static extern bool GetWindowRect(IntPtr hWnd, out Rect rc);
        [DllImport("user32.dll")]
        private static extern bool MoveWindow(IntPtr hWnd, int x, int y, int w, int h, bool repaint);
        private struct Rect { public int Left; public int Top; public int Right; public int Bottom; }
    }
}