Windows 11 breaking Development compatibility

[memoarfaa]

• .NET Core Version:

• Have you experienced this same bug with .NET Framework?: Yes

Problem description:

1. MDIParent Window that have Custom WM_NCPAINT Windows Message or its DWMNCRENDERINGPOLICY set to DWMNCRP_DISABLED will add then new Snap layouts in maximize button to Mdi Child Window (how a Child Window can layout all Desktop Windows and layout its parent in Desktop );

2. DwmExtendFrameIntoClientArea Wrong MARGINS

DwmExtendFrameIntoClientArea will Extend Frame to both Client and Non Client area

[DllImport("dwmapi.dll")]
public static extern int DwmExtendFrameIntoClientArea(IntPtr hWnd, ref MARGINS pMarInset);

   [StructLayout(LayoutKind.Sequential)]
        public struct MARGINS
        {
            internal int cxLeftWidth;

            internal int cxRightWidth;

            internal int cyTopHeight;

            internal int cyBottomHeight;

         
            public MARGINS(int cxLeftWidth, int cxRightWidth, int cyTopHeight, int cyBottomHeight) : this()
            {
                this.cxLeftWidth = cxRightWidth;
                this.cxRightWidth = cxRightWidth;
                this.cyTopHeight = cyTopHeight;
                this.cyBottomHeight = cyBottomHeight;
            }

           
        }
          MARGINS m = new MARGINS(8, 8, 31, 8);
            DwmExtendFrameIntoClientArea(Handle,ref m); 

windows 11

Windows 10 and lower

Expected behavior:

Minimal repro:

[merriemcgaw]

We're unlikely to have any control over this particular scenario. These were changes directly to the Win32 API set. I'd be interested to know if this happens in an MFC app, and if so we should certainly file a feedback issue on the Windows team

[merriemcgaw]

@Olina-Zhang if your team can test the MFC scenario that would be super helpful!

[John-Qiao]

@memoarfaa could you please provide your sample project here?

[dreddy-work]

@John-Qiao , it seems Windows fixed this issue in the latest builds. Can you try this issue again with latest windows 11 build?

[John-Qiao]

@dreddy-work I tested it in my Win11 21H2 OS, and the issue1 is not reproduced in my result, please check below gif:

[dreddy-work]

Thanks @John-Qiao for confirming. Closing as this is fixed in latest windows version.