WinUI3 : Understanding WinUI3 desktop app

Question

Hi,

As we can create a WinUI3 app in both the desktop app(win32 app) and the UWP app. What exactly does it mean to create a WinUI3 in a desktop app? As I understand, this app will follow the Win32 App model, that is, the app will not run on sandbox and the app will not have activation and lifecycle management like UWP apps. Is this right?

In this case, How can we use Win32 APIs in this project, and how can we follow the event loop like the WNDPROC callback function instead of Application::Start()?

Thank You

Answer 1

Application::Start replaces the main message loop
As it is a Win32 app, you can have access to the main window WndProc with SetWindowSubclass (for example in some samples I posted in C#, like in MainWindow.xaml.cs, where I needed to intercept particular messages)

I have this wWinMain in the C++ generated code :

int __stdcall wWinMain(HINSTANCE, HINSTANCE, PWSTR, int)  
{  
    {  
        void (WINAPI *pfnXamlCheckProcessRequirements)();  
        auto module = ::LoadLibrary(L"Microsoft.ui.xaml.dll");  
        if (module)  
        {  
            pfnXamlCheckProcessRequirements = reinterpret_cast<decltype(pfnXamlCheckProcessRequirements)>(GetProcAddress(module, "XamlCheckProcessRequirements"));  
            if (pfnXamlCheckProcessRequirements)  
            {  
                (*pfnXamlCheckProcessRequirements)();  
            }  
  
            ::FreeLibrary(module);  
        }  
    }  
  
    winrt::init_apartment(winrt::apartment_type::single_threaded);  
    ::winrt::Microsoft::UI::Xaml::Application::Start(  
        [](auto&&)  
        {  
            ::winrt::make<::winrt::WinUI3_CPP2::implementation::App>();  
        });  
  
    return 0;  
}