Question: Is it already possible to use CMake to build C++ WinUI3 apps?

[llothar]

Is it already possible to use CMake to build C++ WinUI3 apps?

If it is, where can i find an example.
And if not is this on microsofts todo list or will it be left as a todo for the cmake project volunteers?

[pjmlp]

Nope, microsoft/cppwinrt#1080

[fredemmott]

It is - but if you want to use anything that takes a winrt::xaml_type (e.g. Frame.Navigate instead of setting content), you need to implement xamlmetadataprovider yourself. Example using Content: https://github.com/fredemmott/cmake-cpp-winrt-winui3

In a real world hobby project, i've integrated a winui frontend in a mostly cmake project by making cmake call msbuild, but this is nasty: https://github.com/fredemmott/OpenKneeboard/blob/3446befb5c587d60c7c18521f9bf7b42d33a46e5/src/app/app-winui3/CMakeLists.txt + https://github.com/fredemmott/OpenKneeboard/blob/3446befb5c587d60c7c18521f9bf7b42d33a46e5/src/app/app-winui3/app-winui3.vcxproj

And if not is this on microsofts todo list or will it be left as a todo for the cmake project volunteers?

I don't know about plans; as a user, the ideal solution would be for Microsoft to split the xaml compiler out to a separate executable again, then it could be consistently integrated with any build system.

CMake could be altered to support .xaml files in add_executable()/add_library() when using the visual studio generators - though I think this would also need changes to how cmake handles nuget packages as the xaml compiler msbuild dll is provided in nuget packages, rather than the system-wide windows sdk installation

[pjmlp]

That kind of manual workarounds is anything but "supported".

[fredemmott]

Agreed, but “possible”

[StephenLPeters]

It is possible, but not supported, as fredemmott points out. @RealTommyKlein or @evelynwu-msft might be able to share more specifics.

[RealTommyKlein]

It isn't possible right now due to a reliance on build tasks only available via MSBuild. There is an executable version of the Xaml compiler which is planned to ship in Windows App SDK 1.2, but its inputs handled via JSON are also generated via MSBuild - CMake could also generate those input JSONs though. However other MSBuild tasks, like packaging/resource generation, may also need to be ported to an executable form for the scenario to work end to end.

[fredemmott]

I have a mixed cmake/msbuild project (msbuild entirely due to winui3) - admittedly it's a small project, but I've not had any problems with msix packaging or makepri etc from the cmake, if that's what you're referring to

[fredemmott]

With CMake 3.23 (April 2022) and Windows App SDK 1.1 (June 2022), it's possible to build unpackaged self-contained WinUI3 apps with Xaml, with CMake: I've updated https://github.com/fredemmott/cmake-cpp-winrt-winui3 to show this

I've posted issues/areas for improvement at #3863 (comment)