Qml.Net

A Qml integration with .NET

Supported platforms/runtimes:

• Runtimes:
  • .NET Framework
  • .NET Core
  • Mono
• Operating systems
  • Linux
  • OSX
  • Windows

Getting started

dotnet add package Qml.Net

Windows

dotnet add package Qml.Net.WindowsBinaries

OSX

dotnet add package Qml.Net.OSXBinaries

Linux

dotnet add package Qml.Net.LinuxBinaries

Checkout the examples for some inspiration.

Quick overview

Define a .NET type (POCO)

[Signal("customSignal", NetVariantType.String)] // You can define signals that Qml can listen to.
public class QmlType
{
    /// <summary>
    /// Properties are exposed to Qml.
    /// </summary>
    [NotifySignal("stringPropertyChanged")] // For Qml binding/MVVM.
    public string StringProperty { get; set; }

    /// <summary>
    /// Methods can return .NET types.
    /// The returned type can be invoked from Qml (properties/methods/events/etc).
    /// </summary>
    /// <returns></returns>
    public QmlType CreateNetObject()
    {
        return new QmlType();
    }

    /// <summary>
    /// Qml can pass .NET types to .NET methods.
    /// </summary>
    /// <param name="parameter"></param>
    public void TestMethod(QmlType parameter)
    {
    }

    /// <summary>
    /// Qml can also pass Qml/C++ objects that can be invoked from .NET
    /// </summary>
    /// <param name="qObject"></param>
    public void TestMethodWithQObject(dynamic qObject)
    {
        string result = qObject.PropertyDefinedInCpp;
        qObject.MethodDefinedInCpp(result);
    }
    
    /// <summary>
    /// Async methods can be invoked with continuations happening on Qt's main thread.
    /// </summary>
    public async Task<string> TestAsync()
    {
        // On the UI thread
        await Task.Run(() =>
        {
            // On the background thread
        });
        // On the UI thread
        return "async result!"
    }
    
    /// <summary>
    /// .NET can activate signals to send notifications to Qml.
    /// </summary>
    public void ActivateCustomSignal(string message)
    {
        this.ActivateSignal("customSignal", message)
    }
}

Register your new type with Qml.

using (var app = new QGuiApplication(args))
{
    using (var engine = new QQmlApplicationEngine())
    {
        // Register our new type to be used in Qml
        QQmlApplicationEngine.RegisterType<QmlType>("test", 1, 1);
        engine.Load("main.qml");
        return app.Exec();
    }
}

Use the .NET type in Qml

import QtQuick 2.7
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.0
import test 1.1

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    QmlType {
      id: test
      Component.onCompleted: function() {
          // We can read/set properties
          console.log(test.stringProperty)
          test.stringPropertyChanged.connect(function() {
              console.log("The property was changed!")
          })
          test.stringProperty = "New value!"
          
          // We can return .NET types (even ones not registered with Qml)
          var netObject = test.createNetObject();
          
          // All properties/methods/signals can be invoked on "netObject"
          // We can also pass the .NET object back to .NET
          netObject.testMethod(netObject)
          
          // We can invoke async tasks that have continuation on the UI thread
          var task = netObject.testAsync()
          // And we can await the task
          Net.await(task, function(result) {
              // With the result!
              console.log(result)
          })
          
          // We can trigger signals from .NET
          test.customSignal.connect(function(message) {
              console.log("message: " + message)
          })
          test.activateCustomSignal("test message!")
      }
      function testHandler(message) {
          console.log("Message - " message)
      }
    }
}

Currently implemented

• Support for all the basic Qml types and the back-and-forth between them (DateTime, string, etc).
• Reading/setting properties on .NET objects.
• Invoking methods on .NET obejcts.
• Declaring and activating signals on .NET objects.
• async and await with support for awaiting and getting the result from Qml.
• Passing dynamic javascript objects to .NET as dynamic.
• Custom V8 type that looks like an array, but wraps a .NET IList<T> instance, for modification of list in Qml, and performance.

Not implemented (but planned)

• Compiling Qml resource files and bundling them within .NET.
• Passing QObject types to .NET with support for interacting with signals/slots/properties on them.
• .NET Events to signals
• General perf improvements (particularly with reflection).
• Qml debugger for VS and VS Code.
• Yocto meta-layer for .NET Core and Qml.Net (for embedded Linux development).