PLEASE DON’T FLAG AS DUPLICATE! As I found the related Stackoverflow questions, but they didn’t work.

I am creating a window with WindowStyle="None" AllowTransparency="True". So I am trying to make a fully custom window. I tried to make the windows features working with it, like layout bar, animated state change.

I found this answer:

public void Window_SizeChanged(object sender, SizeChangedEventArgs e)
{
    if (this.WindowState == WindowState.Maximized)
    {
        this.BorderThickness = new System.Windows.Thickness(8);
    }
    else
    {
        this.BorderThickness = new System.Windows.Thickness(0);
    }
}

While it is not bad, I would like to solve the root problem if I can. It is because I assume that it will be fixed, and don’t want to change everything back in each of my apps. Also, I don’t know if it’s a Win 11 related problem or other versions have too.

Also I found this answer:

IntPtr myStyle = new IntPtr(WS.WS_CAPTION | WS.WS_CLIPCHILDREN | WS.WS_MINIMIZEBOX | WS.WS_SYSMENU | WS.WS_SIZEBOX | WS.WS_MAXIMIZEBOX); // ADD  "| WS.WS_MAXIMIZEBOX " to enable snap bar
SetWindowLongPtr(new HandleRef(null, handle), GWL_STYLE, myStyle);

This is all and good, but when I add the WS.WS_MAXIMIZEBOX to the myStyle then if I Mmaximize the window, it will be 8 pixels bigger than the screen (minus the taskbar). Now I assume that I searched a lot and I could not find a working answer. On most places I found this answer to work (not for me):

private void WindowLoaded(object sender, RoutedEventArgs e)
{
    handle = new WindowInteropHelper(window).Handle;
    HwndSource.FromHwnd(handle).AddHook(new HwndSourceHook(WindowProc));

    IntPtr myStyle = new IntPtr(WS.WS_CAPTION | WS.WS_CLIPCHILDREN | WS.WS_MINIMIZEBOX | WS.WS_SYSMENU | WS.WS_SIZEBOX | WS.WS_MAXIMIZEBOX); // ADD  "| WS.WS_MAXIMIZEBOX " to enable snap bar
    SetWindowLongPtr(new HandleRef(null, handle), GWL_STYLE, myStyle);
}

private static IntPtr WindowProc(
      System.IntPtr hwnd,
      int msg,
      System.IntPtr wParam,
      System.IntPtr lParam,
      ref bool handled)
{
    switch (msg)
    {
        case 0x0024:/* WM_GETMINMAXINFO */
            WmGetMinMaxInfo(hwnd, lParam);
            handled = true;
            break;
    }
    return (IntPtr)0;
}

public static void WmGetMinMaxInfo(IntPtr hwnd, IntPtr lParam)
{
    MINMAXINFO mmi = (MINMAXINFO)Marshal.PtrToStructure(lParam, typeof(MINMAXINFO));
    int MONITOR_DEFAULTTONEAREST = 0x00000002;
    IntPtr monitor = MonitorFromWindow(hwnd, MONITOR_DEFAULTTONEAREST);
    if (monitor != IntPtr.Zero)
    {
        MONITORINFO monitorInfo = new MONITORINFO();
        GetMonitorInfo(monitor, monitorInfo);
        RECT rcWorkArea = monitorInfo.rcWork;
        RECT rcMonitorArea = monitorInfo.rcMonitor;
        mmi.ptMaxPosition.x = Math.Abs(rcWorkArea.left - rcMonitorArea.left) // + 1;
        mmi.ptMaxPosition.y = Math.Abs(rcWorkArea.top - rcMonitorArea.top) // + 1;
        mmi.ptMaxSize.x = Math.Abs(rcWorkArea.right - rcWorkArea.left) // - 1;
        mmi.ptMaxSize.y = Math.Abs(rcWorkArea.bottom - rcWorkArea.top) // - 1;
    }
    Marshal.StructureToPtr(mmi, lParam, true);
}

So when I remove the WS.WS_MAXIMIZEBOX style then it works.
But I need it for the snap bar.

So when I add it, it ONLY works if I either
mmi.ptMaxSize.y = Math.Abs(rcWorkArea.bottom - rcWorkArea.top) - {number here > 0};
mmi.ptMaxSize.x = Math.Abs(rcWorkArea.bottom - rcWorkArea.top) - {number here > 0};

OR
mmi.ptMaxPosition.y = Math.Abs(rcWorkArea.top - rcMonitorArea.top) + {number here > 0};
mmi.ptMaxPosition.x = Math.Abs(rcWorkArea.top - rcMonitorArea.top) + {number here > 0};

It works if I do any of above. But if I can, I would like not to create a pixel gap on any of the sides.
So I am here seeking for help. How can I make it work without the need of a gap.