Anybody using DwmExtendFrameIntoClientArea?

[SledgeHammer01]

Just using the stock example from Microsoft:

	void MainWindow\_Loaded(object sender, RoutedEventArgs e)
	{
		IntPtr mainWindowPtr = new WindowInteropHelper(this).Handle;
		HwndSource mainWindowSrc = HwndSource.FromHwnd(mainWindowPtr);

		//mainWindowSrc.CompositionTarget.RenderMode = RenderMode.SoftwareOnly;          //  <=== UNCOMMENT THIS LINE

		mainWindowSrc.CompositionTarget.BackgroundColor = Color.FromArgb(0, 0, 0, 0);

		// Get System Dpi
		System.Drawing.Graphics desktop = System.Drawing.Graphics.FromHwnd(mainWindowPtr);

		float DesktopDpiX = desktop.DpiX;
		float DesktopDpiY = desktop.DpiY;

		// Set Margins
		MARGINS margins = new MARGINS();

		// Extend glass frame into client area 
		// Note that the default desktop Dpi is 96dpi. The  margins are 
		// adjusted for the system Dpi.
		margins.cxLeftWidth = Convert.ToInt32(5 \* (DesktopDpiX / 96));
		margins.cxRightWidth = Convert.ToInt32(5 \* (DesktopDpiX / 96));
		margins.cyTopHeight = Convert.ToInt32(((int)90) \* (DesktopDpiX / 96));
		margins.cyBottomHeight = Convert.ToInt32(5 \* (DesktopDpiX / 96));

		int hr = DwmExtendFrameIntoClientArea(mainWindowSrc.Handle, ref margins);
		// 
		if (hr < 0)
		{
			//DwmExtendFrameIntoClientArea Failed
		}
	}

On my machine, I get a white rectangle over the entire window for about 1 second and then the window redraws properly. This code works on .NET 4.5.1, but this seems to have cropped up in .NET 4.5.2.

[Richard Deeming]

Try calling the code from the window's SourceInitialized event[^], which should fire earlier than the Loaded event. You might also need to call DwmEnableBlurBehindWindow to reset the blur effect for the window. Here's the code I use: https://gist.github.com/RichardD2/ef4ee339ce3dcc10264b[^] That lets you enable the glass effect and set up the thickness using two attached properties. There's an additional real-only attached property which indicates whether the glass effect has been applied, which you can use to adapt your styles where necessary.

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"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[SledgeHammer01]

Tried moving it to SourceInitialized and get the same result. 4.5.1 works perfectly and 4.5.2 has the 1 - 2 second start up lag. This isn't even a question of framework targeting, just if you have > 4.5.1 installed on the machine, it happens.