38 lines
1.1 KiB
Markdown
38 lines
1.1 KiB
Markdown
---
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title: Extensions
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slug: /extensions
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---
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OSUI Extensions are a practical way to extend the possibilities with OSUI, Extensions allow for there to be a specific use or functionality that may otherwise be bloat or the opposite behavior of the use case.
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### `screen.extension(&mut self, ext: Extension)`
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You likely noticed that we used this function in the [Hello World App With Velocity](/docs/next/#hello-world-app-with-velocity) example, this function simply allows for structures implementing [Extension](/docs/next/extensions#trait-extension) to be included in the program.
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---
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## `Handler<E: Event>`
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A `Handler` is a `Component` that is called when a specific event is dispatched, typically through a `Extension`.
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### 📦 Usage
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```rust
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rsx!{
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@Handler::new(|widget, t: &TickEvent| {}
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"Hello World"
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}
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```
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---
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## Trait `Extension`
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### `init(&mut self, _screen: Arc<Screen>)`
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Runs right after the Transform component is applied to every widget.
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### `render(&mut self, _scope: &mut RenderScope, _widget: &Arc<Widget>)`
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Runs right before the `Element::render` is called.
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