Update ConverterFilterKind enum to be flags

[kaiguo]

Idea comes from this API review comment https://github.com/microsoft/microsoft-ui-xaml-specs/pull/48/files#r317833889.

ConverterFilterKind is now a flag, that enables us to combine values like below

<CornerRadiusFilterConverter Filter="TopLeft,BottomRight" />

[MikeHillberg]

What's the purpose of ValueOnly?

[kaiguo]

This is to work around the CX binding bug we saw in the email thread. See #1239.

[jevansaks]

[kaiguo]

@jevansaks Looks like CX doesn't support value combinations like Filter="TopLeft,ValueOnly"

Here's the generated code in metadata provider, fromString value is the raw string "TopLeft,ValueOnly", it throws an invalid arg exception. I guess I'll just close this PR and use our existing code?

    XamlMetadataProvider::RegisterXamlType(
        /* Arg1 TypeName */ 
        L"Microsoft.UI.Xaml.Controls.Primitives.CornerRadiusFilterKind",
        /* Arg2 CreateXamlTypeCallback */ 
        []()
        {
            auto xamlType = winrt::make<EnumXamlType>(
                /* Arg 1 - TypeName */ 
                (PCWSTR)L"Microsoft.UI.Xaml.Controls.Primitives.CornerRadiusFilterKind",
                /* Arg 2 - CreateFromString func */ 
                (std::function<winrt::IInspectable(hstring)>)[](hstring fromString)
                {
                    if (fromString == L"None") return box_value(winrt::CornerRadiusFilterKind::None);
                    if (fromString == L"TopLeft") return box_value(winrt::CornerRadiusFilterKind::TopLeft);
                    if (fromString == L"TopRight") return box_value(winrt::CornerRadiusFilterKind::TopRight);
                    if (fromString == L"BottomLeft") return box_value(winrt::CornerRadiusFilterKind::BottomLeft);
                    if (fromString == L"BottomRight") return box_value(winrt::CornerRadiusFilterKind::BottomRight);
                    if (fromString == L"Top") return box_value(winrt::CornerRadiusFilterKind::Top);
                    if (fromString == L"Left") return box_value(winrt::CornerRadiusFilterKind::Left);
                    if (fromString == L"Bottom") return box_value(winrt::CornerRadiusFilterKind::Bottom);
                    if (fromString == L"Right") return box_value(winrt::CornerRadiusFilterKind::Right);
                    if (fromString == L"ValueOnly") return box_value(winrt::CornerRadiusFilterKind::ValueOnly);
                    throw winrt::hresult_invalid_argument();
                });

            return xamlType;
        });

[jevansaks]

Oh, shucks. Yeah let's go with what's in master for this release. Can you file a bug on markup, then circle back on the spec review and say we can't do this because of that bug?

[kaiguo]

Oh, shucks. Yeah let's go with what's in master for this release. Can you file a bug on markup, then circle back on the spec review and say we can't do this because of that bug?

Yeah, will do.