玻璃效果

封装好的帮助类，实现玻璃效果。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Windows;
using System.Windows.Interop;
using System.Windows.Media;

namespace Test
{
    [StructLayout(LayoutKind.Sequential)]
    public struct MARGINS
    {
        public int Left;
        public int Right;
        public int Top;
        public int Bottom;
        public MARGINS(Thickness t)
        {
            Left = (int)t.Left;
            Right = (int)t.Right;
            Top = (int)t.Top;
            Bottom = (int)t.Bottom;
        }
    }

    public class GlassHelper
    {
        [DllImport("dwmapi.dll", PreserveSig = false)]
        static extern void DwmExtendFrameIntoClientArea(
            IntPtr hWnd, ref MARGINS pMarInset);

        [DllImport("dwmapi.dll", PreserveSig = false)]
        static extern bool DwmIsCompositionEnabled();

        public static bool ExtendGlassFrame(Window window, Thickness margin)
        {
            if (!DwmIsCompositionEnabled())
                return false;

            IntPtr hwnd = new WindowInteropHelper(window).Handle;
            if (hwnd == IntPtr.Zero)
                throw new InvalidOperationException(
                    "The Window must be shown before extending glass");

            //Set the backgroud to transparent from both the WPF and Win32 perspectives
            window.Background = Brushes.Transparent;
            HwndSource.FromHwnd(hwnd).CompositionTarget.BackgroundColor = Colors.Transparent;

            MARGINS margins = new MARGINS(margin);
            DwmExtendFrameIntoClientArea(hwnd, ref margins);

            return true;
        }
    }
}

这个方法不仅必须在初始化的时候调用，也必须在禁用或者重新启用桌面合成之后调用。用户操作或者由远程桌面这样的东西触发，都可能导致禁用或者重新启用桌面合成。为了能收到桌面合成事件，你需要截获一条Win32消息(WM_DWMCOMPOSITIONCHANGED)。

调用方法如下

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Interop;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace Test_7_3_2
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        private const int WM_DWMCOMPOSITIONCHANGED = 0x031E;
        public MainWindow()
        {
            InitializeComponent();
        }

        protected override void OnSourceInitialized(EventArgs e)
        {
            base.OnSourceInitialized(e);

            //This can‘t be done any earlier than the SourceInitialized event
            GlassHelper.ExtendGlassFrame(this, new Thickness(-1));

            //Attach a window procedure in order to detect later enabling of desktop composition
            IntPtr hwnd = new WindowInteropHelper(this).Handle;
            HwndSource.FromHwnd(hwnd).AddHook(new HwndSourceHook(WndProc));
        }

        private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            if(msg == WM_DWMCOMPOSITIONCHANGED)
            {
                //Reenable glass
                GlassHelper.ExtendGlassFrame(this, new Thickness(-1));
                handled = true;
            }
            return IntPtr.Zero;
        }
    }
}

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