WPF 无边框窗体改变大小和移动

WIN32 API:

   private const int WM_NCHITTEST = 0x0084;
        private readonly int agWidth = 12; //拐角宽度
        private readonly int bThickness = 4; // 边框宽度
        private Point mousePoint = new Point(); //鼠标坐标
        public enum HitTest : int
        {
            HTERROR = -2,
            HTTRANSPARENT = -1,
            HTNOWHERE = 0,
            HTCLIENT = 1,
            HTCAPTION = 2,
            HTSYSMENU = 3,
            HTGROWBOX = 4,
            HTSIZE = HTGROWBOX,
            HTMENU = 5,
            HTHSCROLL = 6,
            HTVSCROLL = 7,
            HTMINBUTTON = 8,
            HTMAXBUTTON = 9,
            HTLEFT = 10,
            HTRIGHT = 11,
            HTTOP = 12,
            HTTOPLEFT = 13,
            HTTOPRIGHT = 14,
            HTBOTTOM = 15,
            HTBOTTOMLEFT = 16,
            HTBOTTOMRIGHT = 17,
            HTBORDER = 18,
            HTREDUCE = HTMINBUTTON,
            HTZOOM = HTMAXBUTTON,
            HTSIZEFIRST = HTLEFT,
            HTSIZELAST = HTBOTTOMRIGHT,
            HTOBJECT = 19,
            HTCLOSE = 20,
            HTHELP = 21,
        }

        protected override void OnSourceInitialized(EventArgs e)
        {
            base.OnSourceInitialized(e);
            HwndSource hwndSource = PresentationSource.FromVisual(this) as HwndSource;
            if (hwndSource != null)
            {
                hwndSource.AddHook(new HwndSourceHook(this.WndProc));
            }
        }
        protected virtual IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            switch (msg)
            {
                case WM_NCHITTEST:
                    this.mousePoint.X = (lParam.ToInt32() & 0xFFFF);
                    this.mousePoint.Y = (lParam.ToInt32() >> 16);

                    #region 测试鼠标位置

                    // 窗口左上角
                    if (this.mousePoint.Y - this.Top <= this.agWidth
                       && this.mousePoint.X - this.Left <= this.agWidth)
                    {
                        handled = true;
                        return new IntPtr((int)HitTest.HTTOPLEFT);
                    }
                    // 窗口左下角
                    else if (this.ActualHeight + this.Top - this.mousePoint.Y <= this.agWidth
                       && this.mousePoint.X - this.Left <= this.agWidth)
                    {
                        handled = true;
                        return new IntPtr((int)HitTest.HTBOTTOMLEFT);
                    }
                    // 窗口右上角
                    else if (this.mousePoint.Y - this.Top <= this.agWidth
                       && this.ActualWidth + this.Left - this.mousePoint.X <= this.agWidth)
                    {
                        handled = true;
                        return new IntPtr((int)HitTest.HTTOPRIGHT);
                    }
                    // 窗口右下角
                    else if (this.ActualWidth + this.Left - this.mousePoint.X <= this.agWidth
                       && this.ActualHeight + this.Top - this.mousePoint.Y <= this.agWidth)
                    {
                        handled = true;
                        return new IntPtr((int)HitTest.HTBOTTOMRIGHT);
                    }
                    // 窗口左侧
                    else if (this.mousePoint.X - this.Left <= this.bThickness)
                    {
                        handled = true;
                        return new IntPtr((int)HitTest.HTLEFT);
                    }
                    // 窗口右侧
                    else if (this.ActualWidth + this.Left - this.mousePoint.X <= this.bThickness)
                    {
                        handled = true;
                        return new IntPtr((int)HitTest.HTRIGHT);
                    }
                    // 窗口上方
                    else if (this.mousePoint.Y - this.Top <= this.bThickness)
                    {
                        handled = true;
                        return new IntPtr((int)HitTest.HTTOP);
                    }
                    // 窗口下方
                    else if (this.ActualHeight + this.Top - this.mousePoint.Y <= this.bThickness)
                    {
                        handled = true;
                        return new IntPtr((int)HitTest.HTBOTTOM);
                    }
                    else // 窗口移动
                    {
                        handled = true;
                        return new IntPtr((int)HitTest.HTCAPTION);
                    }
                    #endregion
            }
            return IntPtr.Zero;
        }