Download project source code from Github

Background

This is the sequel of my previous article and aims to help the C++ Win32 developer migrate to WinUI3 offered in Windows 10. You have two options to do this:

Don't change your project and call the Bootstrapper API to enable WinUI3.
- Advantages:
  - You only have one executable.
- Disadvantages:
  - You have to install the Windows APP SDK redistributable depending on the WindowsAPP SDK version. This requires administrator rights. If the user somehow removes this from the control panel or there is any incompatibility with any newer version, you are totally screwed, for it won't reinstall again unless cleanly removed by some PowerShell magic. If your app wants to use a newer WindowsAPP SDK version, you have to reinstall the redistributable.
  - You have to create another WinUI project to compile Xaml files
  - Xaml compiled files (xbf) cannot have XAML-level bindings. You practically need to do everything in code.
Create another VCXPROJ and set it to "Self Contained". This will put all files needed to the output directory and you can redistribute them.
- Advantages
  - No admin required, you manage the redistributable files yourself.
  - You have all the XAML tools.
- Disadvantages
  - If running for Windows 7, you have to have two executables. The executable created by the "Self Contained" project is not compatible with Windows < 10.

So, let's go for the second method, of course.

Preparing the Win32 Project

Switch it to C++17 or greater
Change the precompiled header (or create if it's not there) to pch.h/pch.cpp. This is not required, but it will save you time because everything default-generated by Visual Studio has pch.h in it.

Using the Converter

The converter is a XML tool that creates modifications in an existing Win32 project:

Loads the vcxproj
Changes the "ToolsVersion" to 15

Updates your PCH.h to include:

#ifdef Win32_WINUI3
#undef GetCurrentTime
#include <winrt/Windows.Foundation.h>
#include <winrt/Windows.Foundation.Collections.h>
#include <winrt/Windows.Storage.Streams.h>
#include <winrt/Windows.ApplicationModel.Activation.h>
#include <winrt/Microsoft.UI.Composition.h>
#include <winrt/Microsoft.UI.Xaml.h>
#include <winrt/Microsoft.UI.Xaml.Controls.h>
#include <winrt/Microsoft.UI.Xaml.Controls.Primitives.h>
#include <winrt/Microsoft.UI.Xaml.Data.h>
#include <winrt/Microsoft.UI.Xaml.Interop.h>
#include <microsoft.ui.xaml.window.h>
#include <winrt/Microsoft.UI.Xaml.Markup.h>
#include <winrt/Microsoft.UI.Xaml.Media.h>
#include <winrt/Microsoft.UI.Xaml.Navigation.h>
#include <winrt/Microsoft.UI.Xaml.Shapes.h>
#include <winrt/Microsoft.UI.Xaml.Media.h>
#include <winrt/Microsoft.UI.Xaml.Media.Imaging.h>
#include <winrt/Microsoft.UI.Dispatching.h>
#include <wil/cppwinrt_helpers.h>
#include <appmodel.h>
#endif

Installs NuGet packages if not there. At the time of this writing, these are the latest versions, change them when they get updated:

//CppWinRT 
const char* p1v = "2.0.240111.5";
// WIL
const char* p2v = "1.0.231216.1";
// SDK Build Tools
const char* p3v = "10.0.22621.2428";
// AppSdk
const char* p4v = "1.4.231219000";

Create the default Package.appxmanifest
Change the intermediate build directory so WinUI files are built in a new directory
Adds preprocessor definition Win32_WINUI3

Puts the global variables in the project to work with the WinUI project template:

    <CppWinRTOptimized>true</CppWinRTOptimized>
    <CppWinRTRootNamespaceAutoMerge>true</CppWinRTRootNamespaceAutoMerge>
    <AppContainerApplication>false</AppContainerApplication>
    <AppxPackage>true</AppxPackage>
    <ApplicationType>Windows Store</ApplicationType>
    <ApplicationTypeRevision>10.0</ApplicationTypeRevision>
    <WindowsTargetPlatformVersion>10.0</WindowsTargetPlatformVersion>
    <WindowsTargetPlatformMinVersion>10.0.17763.0</WindowsTargetPlatformMinVersion>
    <UseWinUI>true</UseWinUI>
    <WindowsAppSDKSelfContained>true</WindowsAppSDKSelfContained>
    <WindowsPackageType>None</WindowsPackageType>
    <EnableMsixTooling>true</EnableMsixTooling>

Adds the Nuget Stuff:

<Import Project="packages\Microsoft.Windows.SDK.BuildTools.10.0.22621.2428\build\Microsoft.Windows.SDK.BuildTools.props" Condition="Exists('packages\Microsoft.Windows.SDK.BuildTools.10.0.22621.2428\build\Microsoft.Windows.SDK.BuildTools.props')" />
<Import Project="packages\Microsoft.Windows.CppWinRT.2.0.240111.5\build\native\Microsoft.Windows.CppWinRT.props" Condition="Exists('packages\Microsoft.Windows.CppWinRT.2.0.240111.5\build\native\Microsoft.Windows.CppWinRT.props')" />
<Import Project="packages\Microsoft.WindowsAppSDK.1.4.231219000\build\native\Microsoft.WindowsAppSDK.props" Condition="Exists('packages\Microsoft.WindowsAppSDK.1.4.231219000\build\native\Microsoft.WindowsAppSDK.props')" />
<ImportGroup Label="ExtensionTargets">
   <Import Project="packages\Microsoft.WindowsAppSDK.1.4.231219000\build\native\Microsoft.WindowsAppSDK.targets" Condition="Exists('packages\Microsoft.WindowsAppSDK.1.4.231219000\build\native\Microsoft.WindowsAppSDK.targets')" />
   <Import Project="packages\Microsoft.Windows.CppWinRT.2.0.240111.5\build\native\Microsoft.Windows.CppWinRT.targets" Condition="Exists('packages\Microsoft.Windows.CppWinRT.2.0.240111.5\build\native\Microsoft.Windows.CppWinRT.targets')" />
   <Import Project="packages\Microsoft.Windows.ImplementationLibrary.1.0.231216.1\build\native\Microsoft.Windows.ImplementationLibrary.targets" Condition="Exists('packages\Microsoft.Windows.ImplementationLibrary.1.0.231216.1\build\native\Microsoft.Windows.ImplementationLibrary.targets')" />
   <Import Project="packages\Microsoft.Windows.SDK.BuildTools.10.0.22621.2428\build\Microsoft.Windows.SDK.BuildTools.targets" Condition="Exists('packages\Microsoft.Windows.SDK.BuildTools.10.0.22621.2428\build\Microsoft.Windows.SDK.BuildTools.targets')" />
</ImportGroup>

Adds the default assets and copies the pngs:

    <Image Include="Assets\LockScreenLogo.scale-200.png" />
    <Image Include="Assets\SplashScreen.scale-200.png">
      <DeploymentContent>true</DeploymentContent>
    </Image>
    <Image Include="Assets\Square150x150Logo.scale-200.png" />
    <Image Include="Assets\Square44x44Logo.scale-200.png" />
    <Image Include="Assets\Square44x44Logo.targetsize-24_altform-unplated.png" />
    <Image Include="Assets\StoreLogo.png" />
    <Image Include="Assets\Wide310x150Logo.scale-200.png" />

Creates App.xaml, App.xaml.h and App.xaml.cpp:

<?xml version="1.0" encoding="utf-8"?>
<Application
    x:Class="App2.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:App2">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />
                <!-- Other merged dictionaries here -->
            </ResourceDictionary.MergedDictionaries>
            <!-- Other app resources here -->
        </ResourceDictionary>
    </Application.Resources>
</Application>

#pragma once

#include "App.xaml.g.h"

namespace winrt::%s::implementation
{
    struct App : AppT<App>
    {
        App();

        void OnLaunched(Microsoft::UI::Xaml::LaunchActivatedEventArgs const&);

    private:
        winrt::Microsoft::UI::Xaml::Window window{ nullptr };
    };
}

#include "pch.h"
#include "App.xaml.h"
// #include "MainWindow.xaml.h"

using namespace winrt;
using namespace Microsoft::UI::Xaml;

// To learn more about WinUI, the WinUI project structure,
// and more about our project templates, see: http://aka.ms/winui-project-info.

namespace winrt::%s::implementation
{
    App::App()
    {
#if defined _DEBUG && !defined DISABLE_XAML_GENERATED_BREAK_ON_UNHANDLED_EXCEPTION
        UnhandledException([](IInspectable const&, UnhandledExceptionEventArgs const& e)
        {
            if (IsDebuggerPresent())
            {
                auto errorMessage = e.Message();
                __debugbreak();
            }
        });
#endif
    }

    /// <summary>
    /// Invoked when the application is launched.
    /// </summary>
    /// <param name="e">Details about the launch request and process.</param>
    void App::OnLaunched([[maybe_unused]] LaunchActivatedEventArgs const& e)
    {
        // window = make<MainWindow>();
        // window.Activate();
    }
}

Finally, it saves the new project as a Win32ProjectWUI.vcxproj, which you can add to the solution.

Adding WinUI Stuff

The project still runs WinMain and your Win32 code. To add e.g., a Window

Add New Item -> WinUI -> Blank Window
Edit the XAML, IDL, H and CPP as usual to create the window

Do the WinMain init stuff in WinUI style instead:

WinMain 
#ifdef Win32_WINUI3
 {
     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::your_project_namespace::implementation::App>();
     });

This Start() call will only return when there are no windows visible. So now, you can edit the app.xaml.h to include, for example, blankwindow.xaml.h and to show the window in the OnLaunched method:

window = make<winrt::your_namespace::BlankWindow>();
window.Activate();

The Code

The code contains a sample Win32 project and the converter. The converter will create a WUI vcxproj file which you can add to the project and work to it as described.

Have fun!

History

21^st January, 2024: First release

Convert a Win32 Project to WinUI3 Automatically