Modern is now available for download from GitHub. This is the first public preview of the Modern project and I look forward to your feedback!
Here it is: https://github.com/kennykerr/modern
I would like to thank the developers who tested private builds or contributed in one way or another including James Clarke, Ales Holecek, James McNellis, Jeremiah Morrill, Larry Osterman, Raffaele Rialdi, John Sheehan, Kirk Shoop, and Charles Torre. Your feedback helped to shape my understanding of the Windows Runtime and the modern C++ language projection.
What is Modern?
Modern is a Standard C++ language projection for the Windows Runtime. The Modern compiler produces a header-only library designed to provide Standard C++ developers with first-class access to the Windows API. As I’ve previously shown, Modern provides a classy type system to target the Windows platform with standard C++.
Need a simple example? The Windows.Foundation namespace provides the Uri class with its constructor accepting a string argument. The C++ developer can call this in the most natural way:
using namespace Windows::Foundation;
The Uri class also provides the CombineUri method, which returns another Uri object:
Uri combined = first.CombineUri(L"articles");
And it provides a way to get the canonical representation as a string:
String string = combined.ToString();
That’s all there is to it. No pointers or hats, no reference counting or error codes, nothing that isn’t straightforward and natural to the casual C++ developer.
But I need more power!
Sure thing. Modern provides a library-based language projection. That means you can drill down as far as you want to go. Creating a Windows Runtime class involves the use of an activation factory.
auto factory = GetActivationFactory<Uri, IUriRuntimeClassFactory>();
If you’ve ever tried calling the operating system’s RoGetActivationFactory function you’ll know what a saving this is. With the factory in hand, I can call the logical construction method to create the Uri object:
Uri uri = factory.CreateUri(L"http://kennykerr.ca/");
Not satisfied with the Uri class? You can just ask for Uri’s default interface:
IUriRuntimeClass default = uri;
But if you do that, you’ll notice that IUriRuntimeClass doesn’t provide the ToString method. This comes courtesy of the IStringable interface also provided by the Uri class. No problem, we can just query for it:
IStringable stringable = default.As<IStringable>();
String string = stringable.ToString();
The Windows Runtime is built on the essentials of COM. That means IUnknown** and lots of HRESULTs, right? Wrong. Modern takes advantage of C++11 and beyond to provide a truly modern language projection for the Windows Runtime. So while it is still COM under the hood, a C++ developer should think in terms of references rather than pointers. Practically nothing is off limits to the developer hungry for power, but you don’t need to sacrifice productivity or safety along the way. About the only thing that Modern prohibits is explicit reference counting. It uses C++11’s move semantics to handle reference counting reliably and sparingly. So, given an IUnknown reference:
IUnknown unknown = uri;
I can call the modern equivalent of IUnknown’s QueryInterface:
IUriRuntimeClass uri = unknown.As<IUriRuntimeClass>();
But there’s no AddRef or Release methods. You can even retrieve the underlying interface pointer and call QueryInterface directly:
HRESULT hr = unknown->QueryInterface(set(uri));
But even here the reference counting is hidden away. The uri object receiving the new reference takes care of its own reference counting and the AddRef and Release virtual functions are still inaccessible. So while all of the underlying ABI virtual functions are just a -> away, the reference counting is safely and efficiently taken care of by the library and the compiler.
What if you still desperately need to shoot yourself in the foot? No problem, just get the naked COM interface pointer:
ABI::Windows::Foundation::IUriRuntimeClass * danger = get(uri);
The rabbit hole goes deeper still but I’ll leave it there for the moment.
The GitHub repository includes library sets for developing apps for Windows 8.1 and Windows 10. It includes full projections containing everything you might need to build anything you can imagine, but it also contains smaller library sets for scenarios where you might not need XAML or just want to use the Windows Runtime from a desktop app, console, or service.
You can use this public preview to build XAML apps or apps directly with CoreWindow. You can write console and desktop apps that just happen to use Windows Runtime components but don’t rely on an app container or core dispatcher. It’s up to you.
I am not releasing the Modern compiler at this time. The compiler is required for component development, to produce updated library sets, as well as project templates.
Support for binary composition, required by XAML, is currently experimental. This is likely where I’ll be spending a lot more time improving the language projection. You can however write a simple XAML app and take advantage of the existing support for binary composition. An example is provided on GitHub.
XAML also requires a limited form of reflection. This is mostly working but it needs a bit more time to mature and I need to figure out how XAML designer support can be integrated.
Support for creating collections is in the process of being rewritten and I’ll be including that in an upcoming drop. You can of course consume collections produced by the Windows API, but you cannot create your own collections very easily. Expect this in the next update.
Windows Runtime structures are currently projected quite sparsely. In particular, better support for Numerics is coming.
Clang support is experimental. The current Clang build for Windows doesn’t work too well with the RTM build of Visual Studio 2015. Debugging is not integrated and there is a mismatch between the Clang and CL compiler options.
Visual Studio and the IntelliSense engine still struggles a bit with the large headers and a lot of the metaprogramming, but the compiler is satisfied and that’s what counts. This is the reason why the Modern library is spread out across a number of headers rather than just shipping in a single header file. I’ve done a lot of work to simplify the code. Earlier builds of the language projection took a few minutes to precompile. The code was beautiful with elegant templates but compile time was a killer. I’m actively working on reducing precompile time, but it is already quite reasonable.
Finally, I was hoping to secure some kind of corporate sponsorship for the Modern project but that has not materialized. This means that I’ll be updating Modern as I have free time to commit to the project.