Windows 10: Microsoft's Project Reunion preview arrives to make writing apps easier

Microsoft makes progress on its plan to bring old Windows apps together with modern ones.

Microsoft’s Project Reunion: What’s still missing?

Microsoft has released the version 0.1 preview of Project Reunion, its set of software tools to help developers bridge the gap between the interfaces for legacy Win32 apps and new Universal Windows Platform (UWP) interfaces.

Microsoft announced Project Reunion at its Build 2020 conference this May as an application protocol interface (API) that marries Win32 and UWP. 

It's been almost a decade since Microsoft promised developers the ability to run legacy and modern UWP apps on Windows, starting with Windows 8 in Microsoft's first shot against Apple's iPad and the then new world of touch-enabled tablets and its subsequent Windows 10 convertible laptops.  

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Project Reunion builds on Microsoft changing the name of the Win32 API to the Windows API, and then rolling that API into the UWP API, so developers can add modern features to desktop apps.

The initial releases from Project Reunion included previews of the WinUi 3 UI framework for Windows 10 and WebView 2 for bringing web content into an app. They're both open-source libraries that developers can bring to their own code. 

Microsoft's ambition is to give Windows 10 developers libraries so they can target all the one billion Windows 10 PCs rather than just the devices on the latest Windows 10 builds. 

However, a lot has changed even since the release of the first building blocks of Project Reunion. Apple now has its first Arm-based silicon M1 Mac computers that run iOS and macOS apps. 

These machines are beating the performance of Windows on Arm hardware, such as Microsoft's Surface Pro X, which uses a chip co-developed by Qualcomm and Microsoft. Apple is already building successors to M1 that are aimed at outperforming Intel's higher-end processors

Microsoft's Project Reunion is still in its very early stages, but the company is planning to provide a roadmap of the project in 2021 and will be leaning on contributors via GitHub to improve the project.  

The preview release, available via GitHub and Microsoft's NuGet package manager, "lays the foundation for Project Reunion's runtime distribution" and some "plumbing" that makes sure Windows 10 developer apps can use Project Reunion APIs, according to Microsoft.

In the coming months, Microsoft plans to add Windowing and Storage APIs, as well as improve performance. Microsoft notes the preview is not recommended for use on production PCs.

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The release includes a Hello World sample to test Project Reunion APIs and DirectWriteCore. 

"DirectWriteCore brings best-in-class text layout and rendering to your app and reduces the implementation cost across all Windows versions and other platforms because it is cross-platform and works downlevel," Microsoft notes. 

It also includes the WinUI 3 Preview 3, which Microsoft released in November and the Windows 8-era Modern Resources Toolkit (MRT) Core to help make apps launch faster. 

Microsoft promises that Project Reunion will help developers modernize existing apps written in C++, .NET – including WPF, Windows Forms, and UWP – or React Native.