ZIm/crates/gpui/src/elements/component.rs

use std::marker::PhantomData;

use pathfinder_geometry::{rect::RectF, vector::Vector2F};

use crate::{
    AnyElement, Element, LayoutContext, PaintContext, SceneBuilder, SizeConstraint, View,
    ViewContext,
};

use super::Empty;

pub trait GeneralComponent {
    fn render<V: View>(self, v: &mut V, cx: &mut ViewContext<V>) -> AnyElement<V>;
    fn element<V: View>(self) -> ComponentAdapter<V, Self>
    where
        Self: Sized,
    {
        ComponentAdapter::new(self)
    }
}

pub trait StyleableComponent {
    type Style: Clone;
    type Output: GeneralComponent;

    fn with_style(self, style: Self::Style) -> Self::Output;
}

impl GeneralComponent for () {
    fn render<V: View>(self, _: &mut V, _: &mut ViewContext<V>) -> AnyElement<V> {
        Empty::new().into_any()
    }
}

impl StyleableComponent for () {
    type Style = ();
    type Output = ();

    fn with_style(self, _: Self::Style) -> Self::Output {
        ()
    }
}

pub trait Component<V: View> {
    fn render(self, v: &mut V, cx: &mut ViewContext<V>) -> AnyElement<V>;

    fn element(self) -> ComponentAdapter<V, Self>
    where
        Self: Sized,
    {
        ComponentAdapter::new(self)
    }
}

impl<V: View, C: GeneralComponent> Component<V> for C {
    fn render(self, v: &mut V, cx: &mut ViewContext<V>) -> AnyElement<V> {
        self.render(v, cx)
    }
}

// StylableComponent -> GeneralComponent
pub struct StylableComponentAdapter<C: Component<V>, V: View> {
    component: C,
    phantom: std::marker::PhantomData<V>,
}

impl<C: Component<V>, V: View> StylableComponentAdapter<C, V> {
    pub fn new(component: C) -> Self {
        Self {
            component,
            phantom: std::marker::PhantomData,
        }
    }
}

impl<C: GeneralComponent, V: View> StyleableComponent for StylableComponentAdapter<C, V> {
    type Style = ();

    type Output = C;

    fn with_style(self, _: Self::Style) -> Self::Output {
        self.component
    }
}

// Element -> Component
pub struct ElementAdapter<V: View> {
    element: AnyElement<V>,
    _phantom: std::marker::PhantomData<V>,
}

impl<V: View> ElementAdapter<V> {
    pub fn new(element: AnyElement<V>) -> Self {
        Self {
            element,
            _phantom: std::marker::PhantomData,
        }
    }
}

impl<V: View> Component<V> for ElementAdapter<V> {
    fn render(self, _: &mut V, _: &mut ViewContext<V>) -> AnyElement<V> {
        self.element
    }
}

// Component -> Element
pub struct ComponentAdapter<V: View, E> {
    component: Option<E>,
    element: Option<AnyElement<V>>,
    phantom: PhantomData<V>,
}

impl<E, V: View> ComponentAdapter<V, E> {
    pub fn new(e: E) -> Self {
        Self {
            component: Some(e),
            element: None,
            phantom: PhantomData,
        }
    }
}

impl<V: View, C: Component<V> + 'static> Element<V> for ComponentAdapter<V, C> {
    type LayoutState = ();

    type PaintState = ();

    fn layout(
        &mut self,
        constraint: SizeConstraint,
        view: &mut V,
        cx: &mut LayoutContext<V>,
    ) -> (Vector2F, Self::LayoutState) {
        if self.element.is_none() {
            let element = self
                .component
                .take()
                .expect("Component can only be rendered once")
                .render(view, cx.view_context());
            self.element = Some(element);
        }
        let constraint = self.element.as_mut().unwrap().layout(constraint, view, cx);
        (constraint, ())
    }

    fn paint(
        &mut self,
        scene: &mut SceneBuilder,
        bounds: RectF,
        visible_bounds: RectF,
        _: &mut Self::LayoutState,
        view: &mut V,
        cx: &mut PaintContext<V>,
    ) -> Self::PaintState {
        self.element
            .as_mut()
            .expect("Layout should always be called before paint")
            .paint(scene, bounds.origin(), visible_bounds, view, cx)
    }

    fn rect_for_text_range(
        &self,
        range_utf16: std::ops::Range<usize>,
        _: RectF,
        _: RectF,
        _: &Self::LayoutState,
        _: &Self::PaintState,
        view: &V,
        cx: &ViewContext<V>,
    ) -> Option<RectF> {
        self.element
            .as_ref()
            .and_then(|el| el.rect_for_text_range(range_utf16, view, cx))
    }

    fn debug(
        &self,
        _: RectF,
        _: &Self::LayoutState,
        _: &Self::PaintState,
        view: &V,
        cx: &ViewContext<V>,
    ) -> serde_json::Value {
        serde_json::json!({
            "type": "ComponentAdapter",
            "child": self.element.as_ref().map(|el| el.debug(view, cx)),
        })
    }
}