Fix System.OverflowException in WindowChromeWorker._HandleNCHitTest

[lindexi]

Fixes #6777

Description

The lParam may be the int 64 value which will throw OverflowException when cast to int 32. We only use the int32 part inside the int64, so it's safe for us to use ToInt64 first and then cast to int32.

And I think this fix is safe. Because the HandleWmNcHitTestMsg which handle the NCHitTest will call the NativeMethods.SignedLOWORD method. The SignedLOWORD will cast to long then cast to int32.

wpf/src/Microsoft.DotNet.Wpf/src/Shared/MS/Win32/NativeMethodsCLR.cs

Lines 6208 to 6210 in 7add0fc

	public static int SignedLOWORD(IntPtr n) {
	return SignedLOWORD( unchecked((int)(long)n) );
	}

Customer Impact

See #6777

Regression

None.

Testing

Just the CI.

And I pick the code to dotnet-campus/dotnetCampus.CustomWpf#20 and I build the private version to test this by my application.

Risk

Low. It is safe for us to use IntPtr.ToInt64 and cast the long to int.

Microsoft Reviewers: Open in CodeFlow

[miloush]

The comments are not very useful on their own. If you want to include any, it would be better to say what's going on, like "// avoid overflow for negative coordinates (#6777)".

Otherwise looks good to me.

[lindexi]

Thank you @miloush and I fixed it.

[dipeshmsft]

@lindexi thank you for the contribution. @miloush thanks for your review comments.

[lindexi]

Thank you @dipeshmsft