Qt moves forward on toolkit for .NET-C++ interoperability

Qt Group is moving forward with Qt/.NET, a proposed toolkit for interoperability between C++ and Microsoft’s .NET software development platform.

The toolkit includes a Qt-based custom native host for managing assemblies, along with a native-to-managed adapter module providing interoperability services such as instance method invocation, event notification, and object-lifecycle management, according to an August 30 blog post. Qt/.NET’s proposed plan for Qt and .NET interoperability includes implementing C# interfaces in C++ and defining .NET types that extend Qt classes.  

The toolkit enables native object encapsulation. By extending the QDotNETInterface, C++ objects can become accessible to .NET as implementations of C# interfaces, QT said. The Qt/.NET adapter achieves this by offering a managed object to serve as a proxy of the native implementation. This proxy is created by the QDotNETInterface constructor and contains a list of callbacks provided as interface member implementations. From a managed code perspective, the proxy implements the interface and members that are invoked by other .NET objects. Also, Qt classes can be extended in .NET.

Ongoing work in the Qt/.NET project includes the development of code generation for boilerplate native code. In a June 2023 blog post, Qt demonstrated how Qt/.NET can create QObject-based wrapper classes for managed types, including the possibility of accessing properties of .NET as QObject properties and converting .NET events to QObject signals.