AcrylicWindow - Extension of MetroWindow with BlurBehind and compatibility with both MahApps and MaterialDesignInXamlToolkit

AcrylicWindow.cs

/// <summary>
/// Extended MetroWindow with BlurBehind and compatibility with both MahApps and MaterialDesignInXamlToolkit
/// </summary>
public class AcrylicWindow : MetroWindow
{
	internal enum AccentState
	{
		ACCENT_DISABLED = 1,			// Disabled
		ACCENT_ENABLE_GRADIENT = 0,		// No idea, it's gray no matter what
		ACCENT_ENABLE_TRANSPARENTGRADIENT = 2,	// Painted with accent colour
		ACCENT_ENABLE_BLURBEHIND = 3,		// Blurbehind effect
		ACCENT_INVALID_STATE = 4		// Invalid state
	}

	[StructLayout(LayoutKind.Sequential)]
	internal struct AccentPolicy
	{
		public AccentState AccentState;
		public int AccentFlags;
		public int GradientColor;
		public int AnimationId;
	}

	[StructLayout(LayoutKind.Sequential)]
	internal struct WindowCompositionAttributeData
	{
		public WindowCompositionAttribute Attribute;	// Query attributes
		public IntPtr Data;														// Data buffer
		public int SizeOfData;												// Data size
	}

	internal enum WindowCompositionAttribute    // Same as NtUserGetWindowCompositionAttribute?
	{
		WCA_ACCENT_POLICY = 19
	}

	public AcrylicWindow() : base() {

		// Transparency is required for this to work
		this.AllowsTransparency = true;

	}

	/// <summary>
	/// Sets various DWM window attributes
	/// </summary>
	/// <param name="hwnd">The window to modify</param>
	/// <param name="data">Pointer to the structure with the attribute data</param>
	/// <returns>    Nonzero on success, zero otherwise. You can call GetLastError on failure.</returns>
	[DllImport("user32.dll")]
	internal static extern int SetWindowCompositionAttribute(IntPtr hwnd, ref WindowCompositionAttributeData data);

	private bool isDarkTheme = false;
	
	/// <summary>
	/// This property can be used to find out if the current window is using the dark theme
	/// </summary>
	public bool IsDarkTheme
	{
		get { return isDarkTheme; }
		private set { isDarkTheme = value; }
	}

	/// <summary>
	/// Copy the current MahApps theme to MaterialDesignTheme
	/// </summary>
	public void FixMaterialDesignTheme()
	{
		// Detect the current theme
		ControlzEx.Theming.Theme currentTheme = ThemeManager.Current.DetectTheme(Application.Current);
		IsDarkTheme = currentTheme.BaseColorScheme.ToUpperInvariant() == "DARK";

		// Compatibility for MaterialDesignTheme
		var paletteHelper = new PaletteHelper();
		ITheme theme = paletteHelper.GetTheme();
		IBaseTheme baseTheme = IsDarkTheme ? new MaterialDesignDarkTheme() : (IBaseTheme)new MaterialDesignLightTheme();
		theme.SetBaseTheme(baseTheme);
		theme.SetPrimaryColor(currentTheme.PrimaryAccentColor);
		theme.SetSecondaryColor(currentTheme.PrimaryAccentColor);
		paletteHelper.SetTheme(theme);

		// Set correct ThemeBackground and background transparency
		this.SetResourceReference(BackgroundProperty, "MahApps.Brushes.ThemeBackground");
		var color = this.Background.Clone();
		color.Opacity = 0.90;
		this.Background = color;
	}

	/// <summary>
	/// Invoked whenever application code or internal processes (such as a rebuilding layout pass) call ApplyTemplate. 
	/// </summary>
	public override void OnApplyTemplate()
	{
		base.OnApplyTemplate();
		EnableBlurBehind();

		// Set theme for whole window
		ThemeManager.Current.ThemeSyncMode = ThemeSyncMode.SyncAll;
		ThemeManager.Current.SyncTheme();

		ThemeManager.Current.ThemeChanged += Current_ThemeChanged;

		FixMaterialDesignTheme();
	}

	/// <summary>
	/// Called when the windows theme changes
	/// </summary>
	/// <param name="sender"></param>
	/// <param name="e"></param>
	private void Current_ThemeChanged(object sender, ControlzEx.Theming.ThemeChangedEventArgs e)
	{
		FixMaterialDesignTheme();
	}

	/// <summary>
	/// Enables BlurBehind for our fancy window
	/// </summary>
	internal void EnableBlurBehind()
	{
		var windowHelper = new WindowInteropHelper(this);

		var accent = new AccentPolicy();
		var accentStructSize = Marshal.SizeOf(accent);
		accent.AccentState = AccentState.ACCENT_ENABLE_BLURBEHIND;
		accent.AccentFlags = 2;
		accent.GradientColor = 0x00FFFFFF;

		var accentPtr = Marshal.AllocHGlobal(accentStructSize);
		Marshal.StructureToPtr(accent, accentPtr, false);

		var data = new WindowCompositionAttributeData();
		data.Attribute = WindowCompositionAttribute.WCA_ACCENT_POLICY;
		data.SizeOfData = accentStructSize;
		data.Data = accentPtr;

		SetWindowCompositionAttribute(windowHelper.Handle, ref data);

		Marshal.FreeHGlobal(accentPtr);
	}
}

App.xaml

<Application.Resources>
    <ResourceDictionary>
      <ResourceDictionary.MergedDictionaries>

        <!-- This should be all you need to setup the color theme -->
        <materialDesignMahApps:MahAppsBundledTheme x:Name="mahAppsBundledTheme" BaseTheme="Inherit" PrimaryColor="DeepPurple" SecondaryColor="Purple"/>

        <!-- MahApps -->
        <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Controls.xaml" />
        <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Fonts.xaml" />

        <!-- Material Design -->
        <ResourceDictionary Source="pack://application:,,,/MaterialDesignThemes.Wpf;component/Themes/MaterialDesignTheme.Defaults.xaml" />

        <!-- Material Design: MahApps Compatibility -->
        <ResourceDictionary Source="pack://application:,,,/MaterialDesignThemes.MahApps;component/Themes/MaterialDesignTheme.MahApps.Defaults.xaml"/>

    </ResourceDictionary.MergedDictionaries>
  </ResourceDictionary>
</Application.Resources>