Making an agile version of a Windows Runtime delegate in C++/WinRT, part 4

This article discusses optimizing a wrapper delegate in C++/WinRT by using context tokens for faster checks instead of comparing COM objects. It highlights the importance of keeping the context alive for accurate comparisons.

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Last time, we wrote a wrapper delegate that checked whether the context it was being invoked from matched the context it was captured from .

if (d.try_as<::INoMarshal>()) { return [d = std::forward<Delegate>(d), context = winrt::capture<IContextCallback>(CoGetObjectContext)](auto&&...args) { if (context == winrt::capture<IContextCallback>(CoGetObjectContext)) { d(std::forward<decltype(args)>(args)...); } else { throw winrt::hresult_error(CO_E_NOT_SUPPORTED); } }; } We did this by comparing context objects.

This obtains the current object context in order to compare it with the original one, and that means an internal Add­Ref , and then we have to explicitly Release it.

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