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windowsc++-winrtwinui

namespace Microsoft vs namespace Windows

I am trying C++/WinRT and the WinUI templates available in VisualStudio. I am confused about namespaces ::winrt::Microsoft and ::winrt::Windows. I only know about the former one because auto-generated callback functions used a type from ::winrt::Microsoft, and wouldn't compile because I passed identically named type from ::winrt::Windows namespace by mistake. I couldn't find more information about ::winrt::Microsoft, couldn't even find official documentation.

From what I can say, ::winrt::Microsoft and ::winrt::Windows have mostly identically named types, but some types are missing from ::winrt::Microsoft. For example, ::winrt::Windows::UI::Colors and ::winrt::Microsoft::UI::Colors both exist, but ::winrt::Windows::UI::Color has no "alternative" in the Microsoft namespace.

Questions:

  • Why do we have 2 almost the same but subtly different namespaces?
  • Under which circumstances do I choose one or the other?
  • Why ::winrt::Microsoft is missing some types?
Solution

  • Windows is the original namespace, where all UI-related types live. Some of those types were 'reinvented' into the Microsoft namespace as part of moving WinUI out of its UWP-only misery.

    If a type is available in the (newer) Microsoft namespace then use that. The transition is not yet complete, so some types are missing.