### QString and QByteArray Operations in Rust

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Demonstrates creating, manipulating, and converting between QString, QByteArray, and Rust's String types. Includes examples of string case changes, trimming, parsing integers, and concatenation.

```rust
use qttypes::{QString, QByteArray};

fn string_operations() {
    // Create QString from various sources
    let s1 = QString::from("Hello, World!");
    let s2 = QString::from(String::from("From String"));
    let s3: QString = "From &str".into();

    // String manipulation
    let upper = s1.to_upper();           // "HELLO, WORLD!"
    let lower = s1.to_lower();           // "hello, world!"
    let trimmed = QString::from("  hello  ").trimmed();  // "hello"
    let simplified = QString::from("  lots\t of\nwhitespace  ").simplified();  // "lots of whitespace"

    // Check properties
    assert!(!s1.is_empty());
    assert!(QString::default().is_null());
    assert_eq!(s1.len(), 13);

    // Conversions
    let rust_string: String = s1.clone().into();
    let utf16_slice: &[u16] = s1.to_slice();

    // Parse numbers
    let num_str = QString::from("42");
    let parsed: i32 = num_str.to_int(10).unwrap();

    // Concatenation
    let mut combined = QString::from("Hello");
    combined.append(QString::from(" World"));
    // Or using operators
    let result = QString::from("Hello") + QString::from(" World");

    // QByteArray operations
    let bytes = QByteArray::from("Hello");
    let as_str = bytes.to_str().unwrap();  // &str
    let as_string = bytes.to_string();      // String
}
```

--------------------------------

### Initializing Qt logging integration in Rust

Source: https://github.com/woboq/qmetaobject-rs/blob/master/README.md

To enable integration with the Rust `log` crate and allow QML's `console.log` messages to be processed, call `qmetaobject::log::init_qt_to_rust()` early in `main()`. Remember to also set up a logging backend like `env_logger`.

```rust
fn main() {
    qmetaobject::log::init_qt_to_rust();
    // don't forget to set up env_logger or any other logging backend.
}
```

--------------------------------

### Configure cpp dependencies

Source: https://github.com/woboq/qmetaobject-rs/blob/master/README.md

Add the cpp crate and build-dependencies to your Cargo.toml.

```toml
[dependencies]
cpp = "0.5"

[build-dependencies]
cpp_build = "0.5"
```

--------------------------------

### Managing Qt Signal Connections with Handles

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Demonstrates how to manage the lifecycle of a signal-slot connection using a connection handle. This allows for explicit disconnection when the connection is no longer needed.

```rust
use qmetaobject:: *
use std::cell::RefCell;

#[derive(QObject, Default)]
struct Counter {
    base: qt_base_class!(trait QObject),
    value: qt_property!(i32; NOTIFY value_changed),
    value_changed: qt_signal!(new_value: i32),

    increment: qt_method!(fn increment(&mut self) {
        self.value += 1;
        self.value_changed(self.value);  // Emit signal with argument
    })
}

// Connection handle for managing connections
fn connection_handle_example() {
    let counter = RefCell::new(Counter::default());
    let cpp_obj = unsafe { QObject::cpp_construct(&counter) };

    let signal = counter.borrow().value_changed.to_cpp_representation(&*counter.borrow());
    let mut handle = unsafe {
        connect(cpp_obj, signal, |_: &i32| {
            println!("Connected!");
        })
    };

    // Check if connection is valid
    assert!(handle.is_valid());

    // Disconnect when no longer needed
    handle.disconnect();
}
```

--------------------------------

### Configure qttypes dependency

Source: https://github.com/woboq/qmetaobject-rs/blob/master/README.md

Add the qttypes crate with the qtquick feature to your Cargo.toml.

```toml
[dependencies]
qttypes = { version = "0.2", features = [ "qtquick" ] }
```

--------------------------------

### Create QML Extension Plugin

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Implement QQmlExtensionPlugin to register custom types for QML. Ensure the plugin URI matches the one used in QML.

```rust
use qmetaobject::*
use std::ffi::CStr;

#[derive(Default, QObject)]
struct MyPlugin {
    base: qt_base_class!(trait QQmlExtensionPlugin),
    plugin: qt_plugin!("org.qt-project.Qt.QQmlExtensionInterface/1.0"),
}

impl QQmlExtensionPlugin for MyPlugin {
    fn register_types(&mut self, uri: &CStr) {
        // Register types when plugin loads
        qml_register_type::<MyCustomType>(uri, 1, 0, cstr!("MyCustomType"));
    }
}

#[derive(Default, QObject)]
struct MyCustomType {
    base: qt_base_class!(trait QObject),
    message: qt_property!(QString),
}
```

--------------------------------

### Connecting Qt Signals to Rust Closures

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Illustrates how to connect Qt signals emitted by a QObject to Rust closures, enabling reactive programming patterns. Requires deriving QObject and defining signals and slots.

```rust
use qmetaobject::*
use std::cell::RefCell;

#[derive(QObject, Default)]
struct Counter {
    base: qt_base_class!(trait QObject),
    value: qt_property!(i32; NOTIFY value_changed),
    value_changed: qt_signal!(new_value: i32),

    increment: qt_method!(fn increment(&mut self) {
        self.value += 1;
        self.value_changed(self.value);  // Emit signal with argument
    })
}

fn connect_example() {
    let counter = RefCell::new(Counter::default());

    // Create C++ object
    let cpp_obj = unsafe { QObject::cpp_construct(&counter) };

    // Connect signal to closure
    let signal = counter.borrow().value_changed.to_cpp_representation(&*counter.borrow());
    unsafe {
        connect(cpp_obj, signal, |new_value: &i32| {
            println!("Value changed to: {}", new_value);
        });
    }

    // Trigger the signal
    counter.borrow_mut().increment();
}
```

--------------------------------

### QVariant Operations in Rust

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Shows how to create QVariant instances from various Rust types and perform type checking and conversions. Useful for handling heterogeneous data in Qt applications.

```rust
use qttypes::{QVariant, QString, QByteArray};

fn variant_operations() {
    // Create QVariant from various types
    let v_int = QVariant::from(42i32);
    let v_float = QVariant::from(3.14f64);
    let v_bool = QVariant::from(true);
    let v_string = QVariant::from(QString::from("Hello"));

    // Check validity
    assert!(v_int.is_valid());
    assert!(!QVariant::default().is_valid());

    // Convert to QByteArray for string representation
    let as_bytes: QByteArray = v_int.to_qbytearray();
    assert_eq!(as_bytes.to_string(), "42");

    // Type checking and conversion
    let int_val: QVariant = 100.into();
    println!("Value: {}", int_val.to_qbytearray());
}
```

--------------------------------

### Embed Resources with qrc! Macro

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Embed files into the binary using the qrc! macro and register them before loading via QmlEngine.

```rust
use qmetaobject::qrc;

// Embed QML files as Qt resources
qrc!(my_resources,
    "qml" as "/"  {
        "main.qml",
        "components/Button.qml" as "Button.qml",
    }
);

// With explicit base directory
qrc!(pub app_resources,
    "assets/qml" as "/qml" {
        "App.qml",
        "views/HomeView.qml",
    }
);

fn main() {
    // Register resources before using
    my_resources();
    app_resources();

    let mut engine = QmlEngine::new();

    // Load from resource path
    engine.load_url(QUrl::from(QString::from("qrc:/main.qml")));

    engine.exec();
}
```

--------------------------------

### Apply qrep porting patches

Source: https://github.com/woboq/qmetaobject-rs/blob/master/examples/rqbg/README.md

Commands to clone the qrep repository, checkout the specific commit, and apply the migration patches.

```bash
git clone https://invent.kde.org/vandenoever/qrep
cd qrep
git checkout bdbde040e74819351609581c0d98a59bbfeecbf9 -b qmetaobject-rs
git am ../qmetaobject-rs/examples/rqbg/0001-Port-to-qmetaobject-rs.patch
git am ../qmetaobject-rs/examples/rqbg/0002-Fix-build.patch
cargo run
```

--------------------------------

### Create Custom QML Items with QQuickItem

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Inherit from QQuickItem to implement custom visual components. Requires implementing geometry and event handling methods.

```rust
use qmetaobject::*;

#[derive(Default, QObject)]
struct CustomItem {
    base: qt_base_class!(trait QQuickItem),
    color: qt_property!(QColor; NOTIFY color_changed),
    color_changed: qt_signal!(),
}

impl QQuickItem for CustomItem {
    fn component_complete(&mut self) {
        // Called when the item is fully constructed in QML
        println!("CustomItem completed!");
    }

    fn geometry_changed(&mut self, new_geometry: QRectF, old_geometry: QRectF) {
        println!("Size changed from {:?} to {:?}", old_geometry, new_geometry);
    }

    fn mouse_event(&mut self, event: QMouseEvent) -> bool {
        match event.event_type() {
            QMouseEventType::MouseButtonPress => {
                let pos = event.position();
                println!("Clicked at ({}, {})", pos.x, pos.y);
                true  // Event accepted
            }
            _ => false  // Event not handled
        }
    }

    fn update_paint_node(&mut self, node: SGNode<ContainerNode>) -> SGNode<ContainerNode> {
        // Custom scene graph rendering
        node
    }
}
```

--------------------------------

### Apply mailmodel porting patches

Source: https://github.com/woboq/qmetaobject-rs/blob/master/examples/rqbg/README.md

Commands to clone the mailmodel repository, apply the migration patch, and run the application with a configuration file.

```bash
git clone https://anongit.kde.org/scratch/vandenoever/mailmodel
cd mailmodel
git checkout 87991f1090b57706f5c713c8425684eba144cec2 -b qmetaobject-rs
git am ../qmetaobject-rs/examples/rqbg/mailmodel.patch
cat README.md
# create a configuration file as explained
cargo run config.json
```

--------------------------------

### Configure QmlEngine and Expose Rust Objects

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

The QmlEngine manages the application lifecycle, allows setting context properties, and exposes Rust objects to the QML environment.

```rust
use qmetaobject::prelude::*;
use std::cell::RefCell;

#[derive(QObject, Default)]
struct AppState {
    base: qt_base_class!(trait QObject),
    counter: qt_property!(i32; NOTIFY counter_changed),
    counter_changed: qt_signal!(),
    increment: qt_method!(fn increment(&mut self) {
        self.counter += 1;
        self.counter_changed();
    })
}

fn main() {
    let mut engine = QmlEngine::new();

    // Set a simple property value
    engine.set_property("appTitle".into(), QVariant::from(QString::from("My App")));

    // Set an object property (exposes Rust object to QML)
    let app_state = RefCell::new(AppState::default());
    let pinned = unsafe { QObjectPinned::new(&app_state) };
    engine.set_object_property("appState".into(), pinned);

    // Load QML from a file
    engine.load_file("/path/to/main.qml".into());

    // Or load inline QML data
    engine.load_data(r#"
        import QtQuick 2.6
        Text { text: appTitle }
    "#.into());

    // Add import paths for custom QML modules
    engine.add_import_path("/path/to/qml/modules".into());

    engine.exec();
}
```

--------------------------------

### Create a QObject with Properties, Signals, and Methods

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Use the #[derive(QObject)] macro to define a Rust struct that can be registered and accessed within QML. The struct must include a base class and can define properties, signals, and methods using specific macros.

```rust
use cstr::cstr;
use qmetaobject::prelude::*;

#[derive(QObject, Default)]
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 with a change notification
    name: qt_property!(QString; NOTIFY name_changed),

    // Declare a signal
    name_changed: qt_signal!(),

    // Declare a method callable from QML
    compute_greetings: qt_method!(fn compute_greetings(&self, verb: String) -> QString {
        format!("{} {}", verb, self.name.to_string()).into()
    })
}

fn main() {
    // Register the `Greeter` struct to QML
    qml_register_type::<Greeter>(cstr!("Greeter"), 1, 0, cstr!("Greeter"));

    let mut engine = QmlEngine::new();
    engine.load_data(r#"
        import QtQuick 2.6
        import QtQuick.Window 2.0
        import Greeter 1.0

        Window {
            visible: true
            Greeter {
                id: greeter
                name: "World"
            }
            Text {
                anchors.centerIn: parent
                text: greeter.compute_greetings("Hello")
            }
        }
    "#.into());
    engine.exec();
}
```

--------------------------------

### Date and Time Operations

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Handle date, time, and datetime values using QDate, QTime, and QDateTime. Supports creation from components, extraction of values, and validation. Includes optional integration with the chrono crate for seamless conversion.

```rust
use qttypes::{QDate, QTime, QDateTime};

fn datetime_operations() {
    // Create date
    let date = QDate::from_y_m_d(2024, 6, 15);
    let (year, month, day) = date.get_y_m_d();
    assert!(date.is_valid());

    // Create time
    let time = QTime::from_h_m_s_ms(14, 30, 45, Some(500));
    let (hour, minute, second, ms) = time.get_h_m_s_ms();
    assert!(time.is_valid());

    // Create datetime
    let datetime = QDateTime::from_date_time_local_timezone(date, time);
    let extracted_date = datetime.get_date();
    let extracted_time = datetime.get_time();
    let (d, t) = datetime.get_date_time();

    // From date only
    let date_only = QDateTime::from_date(date);
}
```

```rust
// With chrono feature enabled
#[cfg(feature = "chrono")]
fn chrono_integration() {
    use chrono::{NaiveDate, NaiveTime};

    // Convert from chrono
    let chrono_date = NaiveDate::from_ymd(2024, 6, 15);
    let qdate: QDate = chrono_date.into();

    let chrono_time = NaiveTime::from_hms(14, 30, 45);
    let qtime: QTime = chrono_time.into();

    // Convert to chrono
    let back_to_chrono: NaiveDate = qdate.into();
    let time_back: NaiveTime = qtime.into();
}
```

--------------------------------

### Declare a custom QObject

Source: https://github.com/woboq/qmetaobject-rs/blob/master/README.md

Define a struct that derives QObject and specifies a base class using qt_base_class!.

```rust
#[derive(Default, QObject)]
struct Graph {
    base: qt_base_class!(trait QQuickItem),

    // ...
}
```

--------------------------------

### Exposing a Rust struct to Qt/QML with QMetaObject

Source: https://github.com/woboq/qmetaobject-rs/blob/master/README.md

Use the `QObject` custom derive macro to expose a Rust struct to Qt and QML. Declare properties, signals, and methods using macros like `qt_property!`, `qt_signal!`, and `qt_method!`. Ensure the base class is specified with `qt_base_class!`.

```rust
use cstr::cstr;
use qmetaobject::prelude::*;

// The `QObject` custom derive macro allows to expose a class to Qt and QML
#[derive(QObject, Default)]
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, self.name.to_string()).into()
    })
}

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)
    engine.load_data(r#" 
        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")
            }
        }
    "#.into());
    engine.exec();
}
```

--------------------------------

### Manage Object Lifetimes with QPointer and Pinning

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Use QObjectPinned to ensure objects remain stationary in memory and QPointer for safe weak references. QObjectBox simplifies heap allocation for pinned objects.

```rust
use qmetaobject::*;
use std::cell::RefCell;

#[derive(QObject, Default)]
struct MyObject {
    base: qt_base_class!(trait QObject),
    value: qt_property!(i32),
}

fn pointer_example() {
    let obj = RefCell::new(MyObject::default());

    // Create pinned reference (ensures object won't move)
    let pinned = unsafe { QObjectPinned::new(&obj) };

    // Create C++ object
    let cpp_ptr = pinned.get_or_create_cpp_object();

    // Access through pinned reference
    pinned.borrow_mut().value = 42;
    assert_eq!(pinned.borrow().value, 42);

    // Create QPointer for weak reference
    let qptr = QPointer::from(&*obj.borrow());

    // Check if object is still alive
    if !qptr.is_null() {
        if let Some(pinned_ref) = qptr.as_pinned() {
            println!("Value: {}", pinned_ref.borrow().value);
        }
    }
}

// Using QObjectBox for heap-allocated pinned objects
fn qobject_box_example() {
    let boxed = QObjectBox::new(MyObject::default());
    let pinned = boxed.pinned();

    // Object is automatically pinned and won't move
    pinned.borrow_mut().value = 100;
}
```

--------------------------------

### Set OpenSSL environment variables

Source: https://github.com/woboq/qmetaobject-rs/blob/master/examples/rqbg/README.md

Environment variables to resolve potential compilation errors related to OpenSSL.

```bash
OPENSSL_LIB_DIR=/usr/lib/openssl-1.0 OPENSSL_INCLUDE_DIR=/usr/include/openssl-1.0
```

--------------------------------

### Include C++ headers

Source: https://github.com/woboq/qmetaobject-rs/blob/master/README.md

Use the double curly brace cpp! macro to include C++ headers.

```rust
cpp! {{
    #include <QtQuick/QQuickItem>
}}
```

--------------------------------

### Graphics Types: QRectF, QPointF, QColor, QImage

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Manipulate graphics primitives including points, rectangles, colors, and images. Supports point arithmetic, rectangle containment checks, color conversions, and basic image operations like filling and pixel manipulation.

```rust
use qttypes::{QRectF, QPointF, QSizeF, QColor, QImage, QSize, ImageFormat};

fn graphics_types() {
    // Point and Rectangle
    let point = QPointF { x: 10.0, y: 20.0 };
    let rect = QRectF { x: 0.0, y: 0.0, width: 100.0, height: 50.0 };

    // Point arithmetic
    let offset = QPointF { x: 5.0, y: 5.0 };
    let moved = point + offset;

    // Rectangle operations
    assert!(rect.contains(QPointF { x: 50.0, y: 25.0 }));
    assert!(rect.is_valid());
    let top_left = rect.top_left();

    // Colors
    let red = QColor::from_name("red");
    let custom = QColor::from_rgb(128, 64, 32);
    let with_alpha = QColor::from_rgba(255, 0, 0, 128);
    let from_hsv = QColor::from_hsv(120, 255, 255);  // Green

    // Color components
    let (r, g, b, a) = (custom.get_red(), custom.get_green(), custom.get_blue(), custom.get_alpha());
    let (h, s, v, _) = custom.get_hsva();

    // Images
    let size = QSize { width: 800, height: 600 };
    let mut image = QImage::new(size, ImageFormat::ARGB32);

    // Fill with color
    image.fill(QColor::from_name("white"));

    // Set individual pixels
    image.set_pixel_color(100, 100, QColor::from_name("blue"));
    let pixel = image.get_pixel_color(100, 100);

    // Load from file
    let loaded = QImage::load_from_file(QString::from("/path/to/image.png"));
    let img_size = loaded.size();
    let format = loaded.format();
}
```

--------------------------------

### Create SimpleListModel with SimpleListItem derive macro

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Utilize the SimpleListItem derive macro to quickly generate list models from simple structs. Supports collection-like manipulation and resetting data.

```rust
use qmetaobject::*;

#[derive(SimpleListItem, Default, Clone)]
struct Person {
    name: QString,
    age: i32,
    email: QString,
}

fn main() {
    // Create model from iterator
    let people: SimpleListModel<Person> = vec![
        Person { name: "Alice".into(), age: 30, email: "alice@example.com".into() },
        Person { name: "Bob".into(), age: 25, email: "bob@example.com".into() },
    ].into_iter().collect();

    // Or create and manipulate manually
    let mut model = SimpleListModel::<Person>::default();
    model.push(Person { name: "Charlie".into(), age: 35, email: "charlie@example.com".into() });
    model.insert(0, Person { name: "Diana".into(), age: 28, email: "diana@example.com".into() });
    model.change_line(1, Person { name: "Charlie Updated".into(), age: 36, email: "charlie@example.com".into() });
    model.remove(0);

    // Reset with new data
    model.reset_data(vec![
        Person { name: "Eve".into(), age: 22, email: "eve@example.com".into() },
    ]);

    // Access items
    let first = &model[0];
    for person in model.iter() {
        println!("{}", person.name);
    }
}
```

--------------------------------

### JSON Operations with QJsonObject and QJsonArray

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Utilize QJsonObject, QJsonArray, and QJsonValue for creating, parsing, and serializing JSON data. Supports creation from HashMaps and Vectors, and serialization to compact or pretty-printed strings.

```rust
use qttypes::{QJsonObject, QJsonArray, QJsonValue, QString};
use std::collections::HashMap;

fn json_operations() {
    // Create JSON object
    let mut obj = QJsonObject::default();
    obj.insert("name", QJsonValue::from(QString::from("Alice")));
    obj.insert("age", QJsonValue::from(30.0));
    obj.insert("active", QJsonValue::from(true));

    // Access values
    let name: QString = obj.value("name").into();
    let age: f64 = obj.value("age").into();

    // Create from HashMap
    let mut map = HashMap::new();
    map.insert("key".to_string(), "value".to_string());
    let obj_from_map = QJsonObject::from(map);

    // Create JSON array
    let mut arr = QJsonArray::default();
    arr.push(QJsonValue::from(QString::from("item1")));
    arr.push(QJsonValue::from(QString::from("item2")));
    arr.push(QJsonValue::from(42.0));

    // Or from vector
    let arr_from_vec = QJsonArray::from(vec![
        QJsonValue::from(QString::from("a")),
        QJsonValue::from(QString::from("b")),
    ]);

    // Serialize to JSON string
    let json_str = obj.to_json().to_string();  // Compact
    let pretty_json = obj.to_json_pretty().to_string();  // Indented

    // Nested structures
    let mut root = QJsonObject::default();
    root.insert("data", QJsonValue::from(arr));
    root.insert("metadata", QJsonValue::from(obj_from_map));
}
```

--------------------------------

### Call C++ methods directly

Source: https://github.com/woboq/qmetaobject-rs/blob/master/README.md

Use the unsafe cpp! macro to invoke C++ methods on a QObject.

```rust
impl Graph {
    fn appendSample(&mut self, value: f64) {
        // ...
        let obj = self.get_cpp_object();
        cpp!(unsafe [obj as "QQuickItem *"] {
            obj->setFlag(QQuickItem::ItemHasContents);
        });
        // ...
    }
}
```

--------------------------------

### Implement QAbstractListModel for custom QML list models

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Use the QAbstractListModel trait to define custom models with methods for adding, removing, and updating items. Requires manual management of row insertion and removal notifications.

```rust
use qmetaobject::*;
use std::collections::HashMap;

#[derive(Default, Clone)]
struct TodoItem {
    completed: bool,
    description: String,
}

#[derive(Default, QObject)]
struct TodoModel {
    base: qt_base_class!(trait QAbstractListModel),
    count: qt_property!(i32; READ row_count NOTIFY count_changed),
    count_changed: qt_signal!(),
    list: Vec<TodoItem>,

    add: qt_method!(fn add(&mut self, description: String) {
        let end = self.list.len();
        (self as &mut dyn QAbstractListModel).begin_insert_rows(end as i32, end as i32);
        self.list.push(TodoItem { completed: false, description });
        (self as &mut dyn QAbstractListModel).end_insert_rows();
        self.count_changed();
    }),

    remove: qt_method!(fn remove(&mut self, index: usize) {
        if index < self.list.len() {
            (self as &mut dyn QAbstractListModel).begin_remove_rows(index as i32, index as i32);
            self.list.remove(index);
            (self as &mut dyn QAbstractListModel).end_remove_rows();
            self.count_changed();
        }
    }),

    set_completed: qt_method!(fn set_completed(&mut self, index: usize, completed: bool) {
        if index < self.list.len() {
            self.list[index].completed = completed;
            let idx = (self as &mut dyn QAbstractListModel).row_index(index as i32);
            (self as &mut dyn QAbstractListModel).data_changed(idx.clone(), idx);
        }
    })
}

impl QAbstractListModel for TodoModel {
    fn row_count(&self) -> i32 {
        self.list.len() as i32
    }

    fn data(&self, index: QModelIndex, role: i32) -> QVariant {
        let idx = index.row() as usize;
        if idx < self.list.len() {
            match role {
                USER_ROLE => self.list[idx].completed.into(),
                x if x == USER_ROLE + 1 => QString::from(self.list[idx].description.clone()).into(),
                _ => QVariant::default()
            }
        } else {
            QVariant::default()
        }
    }

    fn role_names(&self) -> HashMap<i32, QByteArray> {
        let mut map = HashMap::new();
        map.insert(USER_ROLE, "completed".into());
        map.insert(USER_ROLE + 1, "description".into());
        map
    }
}
```

--------------------------------

### Manage Threading and Queued Callbacks

Source: https://context7.com/woboq/qmetaobject-rs/llms.txt

Use queued_callback to safely update UI state from background threads. The single_shot function provides a convenient way to execute delayed tasks.

```rust
use qmetaobject::*;
use std::cell::RefCell;

#[derive(QObject, Default)]
struct AsyncWorker {
    base: qt_base_class!(trait QObject),
    result: qt_property!(QString; NOTIFY result_changed),
    result_changed: qt_signal!(),

    start_work: qt_method!(fn start_work(&self, input: String) {
        let qptr = QPointer::from(&*self);

        // Create callback that safely posts to Qt thread
        let set_result = queued_callback(move |value: QString| {
            qptr.as_pinned().map(|this| {
                this.borrow_mut().result = value;
                this.borrow().result_changed();
            });
        });

        // Spawn background thread
        std::thread::spawn(move || {
            // Simulate async work
            std::thread::sleep(std::time::Duration::from_secs(1));
            let result = QString::from(format!("Processed: {}", input));

            // Safely update UI from background thread
            set_result(result);
        });
    })
}

// Single-shot timer
fn timer_example() {
    single_shot(std::time::Duration::from_millis(500), || {
        println!("Timer fired!");
    });
}
```

--------------------------------

### Wrap C++ methods with Rust

Source: https://github.com/woboq/qmetaobject-rs/blob/master/README.md

Define a safe Rust wrapper for C++ functionality using an enum for flags.

```rust
#[repr(C)]
enum QQuickItemFlag {
    ItemClipsChildrenToShape = 0x01,
    ItemAcceptsInputMethod = 0x02,
    ItemIsFocusScope = 0x04,
    ItemHasContents = 0x08,
    ItemAcceptsDrops = 0x10,
}

impl Graph {
    fn set_flag(&mut self, flag: QQuickItemFlag) {
        let obj = self.get_cpp_object();
        assert!(!obj.is_null());
        cpp!(unsafe [obj as "QQuickItem *", flag as "QQuickItem::Flag"] {
            obj->setFlag(flag);
        });
    }

    fn appendSample(&mut self, value: f64) {
        // ...
        self.set_flag(QQuickItemFlag::ItemHasContents);
        // ...
    }
}
```

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