WinUI 3 in an Existing Classic Win32 x86 App

[Mustafa-Hamad]

I’m in implementing WinUI 3, or at least the latest WinUI 2, in a traditional, classic Win32 C/C++ app. I know about XAML Islands, but they seem more tied to WinUI 2, and the latest documentation I’ve seen refers only to that. One big caveat is that I don’t have access to the host executable’s source code—I can only develop DLLs that are dynamically loaded by the engine. There are plenty of hooks, but I’m wondering if this makes things significantly harder or even impossible. I’m a bit lost since there aren’t many resources on this topic and I’m unsure where to start. For reference, I use C++17 and C11, but everything I create has to be in DLL form because I’m trying to implement WinUI as an extension set for a specific engine, where plugins are just DLLs loaded early in the process.

[castorix]

Did you see the MS sample : https://github.com/microsoft/WindowsAppSDK-Samples/tree/main/Samples/Islands ?

[Mustafa-Hamad]

Sorry for the late reply @castorix . I did check the example and have got it working in a Win32 Desktop Application after a lot of modifications. Worst bit was probably manually adding some entires to the proj files...
I didn't test on a DLL yet, but I don't see why it wouldn't work in that.

The problem though is, I still don't understand why the code above doesn't work. The example shows very different ways than what MS documented about XAML Islands. I don't see any mentions of the patterns used in the example linked anywhere in MS Docs.
It's also doing more than the basics. Like having the XAML Compiler setup when I will be placing the components manually anyways (or via the XAML Runtime Parser later on). And in terms of that, I don't see any documentation or examples, I only got it to place some components via pure trial & error.
Many things overlap. Sometimes we use Microsoft., other times it's Windows.

When I check the WinRT Docs, It's a lot of UWP stuff. I do understand that UWP is based on WinRT in a way and WinRT can be used classic Win32 Apps. But I don't see what I actually need...
I feel like I'm probably missing something.. Or is it really all undocumented? I especially need decent documentation and examples on this as my main goal is implenting it all as an Extension-set for a specific Software Development Framework.

[pjmlp]

You are better off doing classical Win32 and COM as extensions, than anything related to WinRT.

It has been rebooted several times since its introduction in Windows 8, many of the old ways are no longer valid, plus WinRT on top of Win32 still hasn't achieved feature parity with WinRT on top of UWP, plus almost all public faces from the early WinRT days have either left Microsoft or moved into Azure and AI business units.