Not able to disable screen capture in WPF using SetWindowDisplayAffinity

Question

Not able to disable screen capture in WPF using SetWindowDisplayAffinity

Vardan Balyan 10

Hi i have a WPF application based on .NET 6 and i want to disable the screen capture for my app and found SetWindowDisplayAffinity but this code is not working in my project. If i debug my code by getting the last error from Marshal.GetLastWin32Error() then it returns value 87 (ERROR_INVALID_PARAMETER).

What am i doing wrong here? Or am i missing something important?

Thanks

Here is my code for reference :

[DllImport("User32.dll", SetLastError = true)]
private static extern bool SetWindowDisplayAffinity(IntPtr hWnd, uint dwAffinity);

public const int WDA_NONE = 0x00000000;
public const int WDA_MONITOR = 0x00000001;
public const int WDA_EXCLUDEFROMCAPTURE = 0x00000011;


private void Window_Loaded(object sender, RoutedEventArgs e)
{ 
    
     SetWindowDisplayAffinity(new WindowInteropHelper(this).Handle, WDA_MONITOR);

     var res = Marshal.GetLastWin32Error();
}

Hui Liu-MSFT 48,681 Microsoft External Staff

Hi,@Vardan Balyan. Welcome Microsoft Q&A.

What are the steps to reproduce your problem? Is it possible to show me the minimal code that can reproduce the problem to reproduce the problem and analysis? I copied the code to my project and used the Snipping Tool to take a screenshot, but I couldn't screenshot the project window.

Or you could try the following code to see if it works.

        [DllImport("User32.dll", SetLastError = true)]
        private static extern bool SetWindowDisplayAffinity(IntPtr hWnd, uint dwAffinity);

        public const int WDA_NONE = 0x00000000;
        public const int WDA_MONITOR = 0x00000001;
        public const int WDA_EXCLUDEFROMCAPTURE = 0x00000011;

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            IntPtr hWnd = IntPtr.Zero;
            HwndSource hwndSource = PresentationSource.FromVisual(this) as HwndSource;

            if (hwndSource != null)
            {
                hWnd = hwndSource.Handle;
            }

            if (hWnd != IntPtr.Zero)
            {
                bool result = SetWindowDisplayAffinity(hWnd, WDA_EXCLUDEFROMCAPTURE);
                if (!result)
                {
                    int errorCode = Marshal.GetLastWin32Error();
                    Console.WriteLine("Error: " + errorCode);
                }
            }
        }

Vardan Balyan 10 Reputation points

2023-05-29T10:18:03.24+00:00

Hi @Hui Liu-MSFT thanks for the reply. I am using the FlyLeaf plugin in the WPF is that something that is blocking the API to work properly here is the sample project url :

https://github.com/SuRGeoNix/Flyleaf/tree/master/Samples/FlyleafPlayer%20(WPF%20Control)%20(WPF)

Also one more thing i have seen somewhere that in order to SetWindowDisplayAffinity to work the AllowsTransparency needs to false is this some kind of requirement in API. And this flag is need to be true for Flyleaf player to work.

Thanks
Hui Liu-MSFT 48,681 Reputation points Microsoft External Staff

2023-05-30T10:01:39.5+00:00

Hi,@Vardan Balyan. Glad to hear you found the cause of the problem.
Vardan Balyan 10 Reputation points

2023-05-30T11:54:57.1266667+00:00

No i was asking you if flyleaf is blocking the API from working in some way, because i have no idea how to make it work with Flyleaf plugin
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Hui Liu-MSFT 48,681 Reputation points Microsoft External Staff

2023-05-31T01:30:55.7533333+00:00

Hi,@Vardan Balyan. For the problem that the third-party Flyleaf plug-in blocks the normal operation of the API, it is recommended that you file an issue here.
Vardan Balyan 10 Reputation points

2023-06-01T07:16:07.85+00:00

Ok, thanks for support @Hui Liu-MSFT

Your answer

Hui Liu-MSFT 48,681 Reputation points Microsoft External Staff

2023-05-29T09:53:24.36+00:00

Hi,@Vardan Balyan. Welcome Microsoft Q&A.

What are the steps to reproduce your problem? Is it possible to show me the minimal code that can reproduce the problem to reproduce the problem and analysis? I copied the code to my project and used the Snipping Tool to take a screenshot, but I couldn't screenshot the project window.

Or you could try the following code to see if it works.

[DllImport("User32.dll", SetLastError = true)] private static extern bool SetWindowDisplayAffinity(IntPtr hWnd, uint dwAffinity); public const int WDA_NONE = 0x00000000; public const int WDA_MONITOR = 0x00000001; public const int WDA_EXCLUDEFROMCAPTURE = 0x00000011; private void Window_Loaded(object sender, RoutedEventArgs e) { IntPtr hWnd = IntPtr.Zero; HwndSource hwndSource = PresentationSource.FromVisual(this) as HwndSource; if (hwndSource != null) { hWnd = hwndSource.Handle; } if (hWnd != IntPtr.Zero) { bool result = SetWindowDisplayAffinity(hWnd, WDA_EXCLUDEFROMCAPTURE); if (!result) { int errorCode = Marshal.GetLastWin32Error(); Console.WriteLine("Error: " + errorCode); } } }
Vardan Balyan 10 Reputation points

2023-05-29T10:18:03.24+00:00

Hi @Hui Liu-MSFT thanks for the reply. I am using the FlyLeaf plugin in the WPF is that something that is blocking the API to work properly here is the sample project url :

https://github.com/SuRGeoNix/Flyleaf/tree/master/Samples/FlyleafPlayer%20(WPF%20Control)%20(WPF)

Also one more thing i have seen somewhere that in order to SetWindowDisplayAffinity to work the AllowsTransparency needs to false is this some kind of requirement in API. And this flag is need to be true for Flyleaf player to work.

Thanks
Hui Liu-MSFT 48,681 Reputation points Microsoft External Staff

2023-05-30T10:01:39.5+00:00

Hi,@Vardan Balyan. Glad to hear you found the cause of the problem.
Vardan Balyan 10 Reputation points

2023-05-30T11:54:57.1266667+00:00

No i was asking you if flyleaf is blocking the API from working in some way, because i have no idea how to make it work with Flyleaf plugin
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Hui Liu-MSFT 48,681 Reputation points Microsoft External Staff

2023-05-31T01:30:55.7533333+00:00

Hi,@Vardan Balyan. For the problem that the third-party Flyleaf plug-in blocks the normal operation of the API, it is recommended that you file an issue here.
Vardan Balyan 10 Reputation points

2023-06-01T07:16:07.85+00:00

Ok, thanks for support @Hui Liu-MSFT

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Not able to disable screen capture in WPF using SetWindowDisplayAffinity

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