Crate qmetaobject[][src]

Expand description

This crate implements binding to the Qt API which allow to use QML from a rust application.


use cstr::cstr;
use qmetaobject::prelude::*;

// The `QObject` custom derive macro allows to expose a class to Qt and QML
struct Greeter {
    // Specify the base class with the qt_base_class macro
    base: qt_base_class!(trait QObject),
    // Declare `name` as a property usable from Qt
    name: qt_property!(QString; NOTIFY name_changed),
    // Declare a signal
    name_changed: qt_signal!(),
    // And even a slot
    compute_greetings: qt_method!(fn compute_greetings(&self, verb: String) -> QString {
        format!("{} {}", verb,

fn main() {
    // Register the `Greeter` struct to QML
    qml_register_type::<Greeter>(cstr!("Greeter"), 1, 0, cstr!("Greeter"));
    // Create a QML engine from rust
    let mut engine = QmlEngine::new();
    // (Here the QML code is inline, but one can also load from a file)
        import QtQuick 2.6
        import QtQuick.Window 2.0
        // Import our Rust classes
        import Greeter 1.0

        Window {
            visible: true
            // Instantiate the rust struct
            Greeter {
                id: greeter;
                // Set a property
                name: "World"
            Text {
                anchors.centerIn: parent
                // Call a method
                text: greeter.compute_greetings("hello")

Basic types

The re-exported crate qttypes contains binding to the most usefull basic types such as QString, QVariant, …

You can also simply use rust type String, but using QString might avoid unecessary conversions in some case.

Meta type

In order to be able to use a type in a signal or method parameter, or as a property type, the type need to implement the QMetaType trait. All the method are provided so you can just implement the QMetaType like this:

use qmetaobject::QMetaType;

#[derive(Default, Clone)]
struct MyPoint(u32, u32);

impl QMetaType for MyPoint {};

With that it is also possible to put the type in a QVariant

Object pinning

Once an object that derives from QObject is exposed to C++, it needs to be pinned, and cannot be moved in memory. Also, since the Qt code can be re-entrant, the object must be placed in a RefCell. The QObjectPinned object is used to enforce the pinning.

If you want to keep pointer to reference, you can use QPointer.


The QML engine only runs in a single thread. And probably all the QObjects needs to be living in the Qt thread. But you can use the queued_callback function to create callback that can be called from any thread and are going to run in the Qt thread.

This can be done like so:

use qmetaobject::prelude::*;

#[derive(QObject, Default)]
struct MyAsyncObject {
    base: qt_base_class!(trait QObject),
    result: qt_property!(QString; NOTIFY result_changed),
    result_changed: qt_signal!(),
    recompute_result: qt_method!(fn recompute_result(&self, name: String) {
        let qptr = QPointer::from(&*self);
        let set_value = qmetaobject::queued_callback(move |val: QString| {
            qptr.as_pinned().map(|this| {
                this.borrow_mut().result = val;
        std::thread::spawn(move || {
            // do stuff asynchronously ...
            let r = QString::from("Hello ".to_owned() + &name);


pub use qttypes;
pub use crate::log::*;
pub use connections::RustSignal;
pub use connections::connect;
pub use connections::Signal;
pub use connections::SignalInner;
pub use future::*;
pub use itemmodel::*;
pub use listmodel::*;
pub use qmetatype::*;
pub use qtdeclarative::*;
pub use qtquickcontrols2::*;
pub use tablemodel::*;


Signals, slots and connections between them.

Logging facilities and forwarding

Module intended for glob import.

Wrappers around QtCore module.


Embed files and made them available to the Qt resource system.

This macro must be used once as a type in a struct that derives from QObject. It is anotate from which QObject like trait it is supposed to derive. the field which it annotate will be an internal property holding a pointer to the actual C++ object

This macro can be used to declare a method which will become a meta method.

Equivalent to the Q_PLUGIN_METADATA macro.

This macro can be used as a type of a field and can then turn this field in a Qt property. The first parameter is the type of this property. Then we can have the meta keywords similar to these found in Q_PROPERTY.

Declares a signal


Wrapper around QBrush class.

Wrapper around QByteArray class.

Wrapper around QColor class.

Wrapper around QDate class.

Wrapper around QDateTime class.

Wrapper around QImage class.

Wrapper around QJsonArray class.

Wrapper around QJsonObject class.

Wrapper around QJsonValue class.

Bindings for QLineF class.

Bindings for QMargins class.

Wrapper around QModelIndex class.

A wrapper around RefCell, whose content cannot be move in memory

A reference to a RefCell, where T is a QObject, which does not move in memory

Same as std::cell::RefMut, but does not allow to move from

Wrapper around QPainter class.

Wrapper around QPen class.

Wrapper around QPixmap class.

Bindings for QPoint class.

Bindings for QPointF class.

A Wrapper around a QPointer

Bindings for QRectF class.

Bindings for QSize class.

Bindings for QSizeF class.

Wrapper around QString class.

Wrapper around QStringList class.

Wrapper around QTime class.

Wrapper around QUrl class.

Wrapper around QVariant class.

Wrapper around QVariantList typedef.

Internal class used to iterate over a QVariantList


Bindings for Qt::BrushStyle enum.

Bindings for QImage::Format enum class.

Bindings for Qt::PenStyle enum.

Bindings for QColor::NameFormat enum class.

Bindings for QColor::Spec enum class.


Refer to the documentation of Qt::UserRole


Trait that is implemented by the QEnum custom derive macro

Trait that is implemented by the QGadget custom derive macro

Trait that is implemented by the QObject custom derive macro


Create the C++ object and return a C++ pointer to a QObject.

Create a callback to invoke a queued callback in the current thread.

Call the callback once, after a given duration.

Type Definitions