WPF 无边框窗体鼠标拖动改变大小和移动

**WPF 处理 Windows 消息的模式和 WinForm 不一样了。Window 类里没有 WndProc 函数了，想要截取 Windows 消息必须借助 HwndSource 添加 Hook。

代码:**

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)
{
    return IntPtr.Zero;
}

OK，WndProc 注册完成之后就可以通过 WndProc 函数完成对Windows消息的处理了。可以发现，这里的 WndProc 和标准的 Win32 消息循环很像，只是多了一个 ref bool handled 参数，对于该参数MSDN是这样说明的： 指示该消息是否已处理的值。如果该消息已处理，请将值设置为 true；否则请将其设置为 false。 在下面我们将会使用到这个参数数。

代码:

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
 
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);
 
        测试鼠标位置#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;
}

从上面的代码可以看出，工作原理很简单：截取 WM_NCHITTEST 消息，获得鼠标坐标，再在你希望的地方返回不同的消息以模拟鼠标的状态即可。需要注意的是，返回消息之前必须将handled 设为 true。告诉系统你已经处理过该消息，不然无效果。 关于 HitTest 是自定义的枚举类，里面包含了鼠标的各种消息。

代码:

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,
}