WINAPI/DWMAPI 不规则形状的模糊窗口

注意：这不是关于无边框窗口的问题。

因此，前几天我在 Windows 7 上浏览“开始”菜单时偶然发现了这个程序：

它是一个本机 Windows 程序，称为“数学输入面板”。现在，我对窗户的形状很好奇。我知道它并不是完全由 DWM 绘制的，因为边框和关闭按钮看起来很可疑，并且窗口没有投影（我启用了投影）。我对这是如何制作的第一个猜测是使用DwmEnableBlurBehindWindow，但我无法想象这适用于不规则的窗户形状，不是吗？ （或者还有其他方法可以做到这一点，或者这完全是微软的魔法？）

这是一个快速组合而成的 WPF 解决方案。它使用hRgnBlur of the DWM_BLURBEHIND http://msdn.microsoft.com/en-us/library/windows/desktop/aa969500.aspx结构和一些互操作。

此示例将在窗口上应用椭圆形背景模糊。

您可以轻松地将其转换为附加属性或行为以实现 MVVM 友好。多听听也是一个好主意WM_DWMCOMPOSITIONCHANGED消息并根据需要重新应用模糊。

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        WindowStyle = WindowStyle.None;
        AllowsTransparency = true;

        SourceInitialized += OnSourceInitialized;
    }

    private void OnSourceInitialized(object sender, EventArgs eventArgs)
    {
        if (!NativeMethods.DwmIsCompositionEnabled())
            return;

        var hwnd = new WindowInteropHelper(this).Handle;

        var hwndSource = HwndSource.FromHwnd(hwnd);
        var sizeFactor = hwndSource.CompositionTarget.TransformToDevice.Transform(new Vector(1.0, 1.0));

        Background = System.Windows.Media.Brushes.Transparent;
        hwndSource.CompositionTarget.BackgroundColor = Colors.Transparent;

        using (var path = new GraphicsPath())
        {
            path.AddEllipse(0, 0, (int)(ActualWidth * sizeFactor.X), (int)(ActualHeight * sizeFactor.Y));

            using (var region = new Region(path))
            using (var graphics = Graphics.FromHwnd(hwnd))
            {
                var hRgn = region.GetHrgn(graphics);

                var blur = new NativeMethods.DWM_BLURBEHIND
                {
                    dwFlags = NativeMethods.DWM_BB.DWM_BB_ENABLE | NativeMethods.DWM_BB.DWM_BB_BLURREGION | NativeMethods.DWM_BB.DWM_BB_TRANSITIONONMAXIMIZED,
                    fEnable = true,
                    hRgnBlur = hRgn,
                    fTransitionOnMaximized = true
                };

                NativeMethods.DwmEnableBlurBehindWindow(hwnd, ref blur);

                region.ReleaseHrgn(hRgn);
            }
        }
    }

    [SuppressUnmanagedCodeSecurity]
    private static class NativeMethods
    {
        [StructLayout(LayoutKind.Sequential)]
        public struct DWM_BLURBEHIND
        {
            public DWM_BB dwFlags;
            public bool fEnable;
            public IntPtr hRgnBlur;
            public bool fTransitionOnMaximized;
        }

        [Flags]
        public enum DWM_BB
        {
            DWM_BB_ENABLE = 1,
            DWM_BB_BLURREGION = 2,
            DWM_BB_TRANSITIONONMAXIMIZED = 4
        }

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

        [DllImport("dwmapi.dll", PreserveSig = false)]
        public static extern void DwmEnableBlurBehindWindow(IntPtr hwnd, ref DWM_BLURBEHIND blurBehind);
    }
}

与以下 XAML 一起使用：

<Window x:Class="WpfTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="200" Width="300" WindowStartupLocation="CenterScreen">

    <Border Background="#800000FF" Margin="30">
        <TextBlock Text="Hello, world!" VerticalAlignment="Center" HorizontalAlignment="Center" />
    </Border>
</Window>

结果是：