Version 0.1.1
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# `osui::extensions`
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The `extensions` module defines the core traits and types for extending OSUI's functionality. It provides a global event bus and lifecycle hooks that allow custom logic to interact with the entire UI application.
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## `Extension` Trait
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The central trait for adding global behaviors to an OSUI application. Any struct implementing this trait can be registered with the `Screen` to receive lifecycle and event callbacks.
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```rust
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pub trait Extension {
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/// Called once when the extension is registered with the `Screen`.
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#[allow(unused)]
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fn init(&mut self, _ctx: &Context) {}
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/// Called when any `Event` is dispatched across the system.
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#[allow(unused)]
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fn event(&mut self, _ctx: &Context, _event: &dyn Event) {}
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/// Called when `Screen::close()` is invoked, before the application terminates.
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#[allow(unused)]
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fn on_close(&mut self) {}
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/// Called before any widgets are rendered in a frame, with a scope for the entire screen.
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#[allow(unused)]
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fn render(&mut self, _ctx: &Context, _scope: &mut RenderScope) {}
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/// Called before a specific widget's `Element::render` method is invoked.
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#[allow(unused)]
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fn render_widget(&mut self, _ctx: &Context, _scope: &mut RenderScope, _widget: &Arc<Widget>) {}
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/// Called after a specific widget's `Element::after_render` method is invoked.
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#[allow(unused)]
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fn after_render_widget(
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&mut self,
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_ctx: &Context,
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_scope: &mut RenderScope,
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_widget: &Arc<Widget>,
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) {}
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}
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```
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## `Event` Trait
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A marker trait for types that can be dispatched as events within the OSUI system. Events are type-erased (`dyn Event`) when dispatched, requiring downcasting to retrieve their specific type.
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```rust
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pub trait Event: Send + Sync {
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/// Returns a type-erased reference to this object, enabling downcasting.
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fn as_any(&self) -> &dyn Any;
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}
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impl<'a> dyn Event + 'a {
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/// Attempts to downcast a dynamic `Event` trait object to a concrete type `T`.
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///
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/// # Type Parameters
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/// * `T`: The concrete event type to downcast to. Must also implement `Event`.
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///
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/// # Returns
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/// `Some(&T)` if the downcast is successful, `None` otherwise.
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pub fn get<T: Event + 'static>(&self) -> Option<&T> {
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self.as_any().downcast_ref()
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}
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}
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```
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## `Context`
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The `Context` struct provides a way for extensions and widgets to interact with the global OSUI `Screen` instance. It holds an `Arc<Screen>` and offers convenience methods for dispatching events, querying widgets, and accessing components.
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```rust
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#[derive(Clone)]
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pub struct Context {
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screen: Arc<Screen>,
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}
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```
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### Associated Methods
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#### `Context::new(screen: Arc<Screen>) -> Self`
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Creates a new `Context` instance.
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**Arguments:**
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* `screen`: An `Arc` to the `Screen` instance that this context will operate on.
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#### `Context::event<E: Event + Clone + 'static>(&self, e: &E)`
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Dispatches an event `e` throughout the OSUI system.
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This will:
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1. Call the `event` method on all widgets (specifically, on any `Handler<E>` components attached to them, and on the `Element::event` method of focused widgets).
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2. Call the `event` method on all registered `Extension`s.
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**Arguments:**
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* `e`: A reference to the event to dispatch.
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**Example:**
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```rust
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use osui::prelude::*;
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// Inside an extension or a component:
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// self.ctx.event(&MyCustomEvent { /* ... */ });
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```
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#### `Context::get_widgets(&self) -> MutexGuard<Vec<Arc<Widget>>>`
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Returns a `MutexGuard` to the `Vec` of `Arc<Widget>` that the `Screen` is currently managing. This allows extensions to iterate over and manipulate the global list of widgets.
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**Returns:**
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A `MutexGuard` providing mutable access to the list of root widgets.
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#### `Context::iter_components<C: Component + 'static + Clone, F: FnMut(&Arc<Widget>, Option<C>)>(&self, mut iterator: F)`
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Iterates over all widgets managed by the `Screen` and applies a provided closure to each widget, along with an `Option` of a cloned component of type `C` if the widget has one.
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**Type Parameters:**
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* `C`: The `Component` type to look for.
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* `F`: The closure to execute for each widget.
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**Arguments:**
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* `iterator`: A closure that takes an `Arc<Widget>` and an `Option<C>`.
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#### `Context::get_components<C: Component + 'static + Clone>(&self) -> Vec<C>`
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Collects all instances of a specific `Component` type from all widgets managed by the `Screen` into a `Vec`.
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**Type Parameters:**
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* `C`: The `Component` type to collect.
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**Returns:**
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A `Vec` containing cloned instances of component `C`.
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#### `Context::render_root(&self, scope: &mut RenderScope)`
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Calls the `render` hook for all registered `Extension`s, allowing them to draw global elements that span the entire screen. This is typically called once per frame before individual widgets are rendered.
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**Arguments:**
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* `scope`: The `RenderScope` representing the entire screen.
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#### `Context::render(&self, w: &Arc<Widget>, scope: &mut RenderScope)`
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Calls the `render_widget` hook for all registered `Extension`s for a specific `widget`. This is invoked during the rendering of each individual widget.
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**Arguments:**
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* `w`: The `Arc<Widget>` currently being rendered.
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* `scope`: The `RenderScope` for `w`.
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#### `Context::after_render(&self, w: &Arc<Widget>, scope: &mut RenderScope)`
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Calls the `after_render_widget` hook for all registered `Extension`s for a specific `widget`. This is invoked after a widget's `Element::after_render` method has completed.
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**Arguments:**
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* `w`: The `Arc<Widget>` that has just finished its `after_render` phase.
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* `scope`: The `RenderScope` for `w`.
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## `Handler<E>` (Component)
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A component that allows a widget to listen for and react to specific `Event` types `E`.
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```rust
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#[derive(Clone)]
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pub struct Handler<E: Event>(Arc<Mutex<dyn FnMut(&Arc<Widget>, &E) + Send + Sync>>);
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```
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### Implementations
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#### `impl<E: Event + 'static> Component for Handler<E>`
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`Handler<E>` implements the `Component` trait, allowing it to be attached to any `Widget`.
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#### `impl<E: Event + 'static> Handler<E>`
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#### `Handler::new<F: FnMut(&Arc<Widget>, &E) + Send + Sync + 'static>(f: F) -> Handler<E>`
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Creates a new `Handler<E>` with the given mutable closure `f`. This closure will be called when an event of type `E` is dispatched.
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**Arguments:**
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* `f`: The closure to execute when the event occurs. It receives the `Arc<Widget>` it's attached to and a reference to the event.
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**Example:**
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```rust
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use osui::prelude::*;
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event!(ButtonClicked);
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rsx! {
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@Handler::new(|widget_arc, event: &ButtonClicked| {
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println!("Button clicked on widget: {:?}", widget_arc);
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});
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Div { "My Button" }
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}
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```
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#### `Handler::call(&self, w: &Arc<Widget>, e: &E)`
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Invokes the internal closure with the provided widget and event. This method is called internally by `Widget::event`.
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**Arguments:**
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* `w`: The `Arc<Widget>` that owns this handler.
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* `e`: The event to process.
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