1use crate::{
  2    element::{AnyElement, Element, IntoElement, Layout, ParentElement},
  3    interactive::{InteractionHandlers, Interactive},
  4    paint_context::PaintContext,
  5    style::{Style, StyleHelpers, Styleable},
  6    ViewContext,
  7};
  8use anyhow::Result;
  9use gpui::{geometry::vector::Vector2F, platform::MouseMovedEvent, LayoutId};
 10use refineable::{CascadeSlot, Refineable, RefinementCascade};
 11use smallvec::SmallVec;
 12use std::{cell::Cell, rc::Rc};
 13
 14pub struct Hoverable<E: Styleable> {
 15    hovered: Rc<Cell<bool>>,
 16    cascade_slot: CascadeSlot,
 17    hovered_style: <E::Style as Refineable>::Refinement,
 18    child: E,
 19}
 20
 21pub fn hoverable<E: Styleable>(mut child: E) -> Hoverable<E> {
 22    Hoverable {
 23        hovered: Rc::new(Cell::new(false)),
 24        cascade_slot: child.style_cascade().reserve(),
 25        hovered_style: Default::default(),
 26        child,
 27    }
 28}
 29
 30impl<E: Styleable> Styleable for Hoverable<E> {
 31    type Style = E::Style;
 32
 33    fn style_cascade(&mut self) -> &mut RefinementCascade<Self::Style> {
 34        self.child.style_cascade()
 35    }
 36
 37    fn declared_style(&mut self) -> &mut <Self::Style as Refineable>::Refinement {
 38        &mut self.hovered_style
 39    }
 40}
 41
 42impl<V: 'static, E: Element<V> + Styleable> Element<V> for Hoverable<E> {
 43    type PaintState = E::PaintState;
 44
 45    fn layout(
 46        &mut self,
 47        view: &mut V,
 48        cx: &mut ViewContext<V>,
 49    ) -> Result<(LayoutId, Self::PaintState)>
 50    where
 51        Self: Sized,
 52    {
 53        Ok(self.child.layout(view, cx)?)
 54    }
 55
 56    fn paint(
 57        &mut self,
 58        view: &mut V,
 59        parent_origin: Vector2F,
 60        layout: &Layout,
 61        paint_state: &mut Self::PaintState,
 62        cx: &mut PaintContext<V>,
 63    ) where
 64        Self: Sized,
 65    {
 66        let bounds = layout.bounds + parent_origin;
 67        self.hovered.set(bounds.contains_point(cx.mouse_position()));
 68
 69        let slot = self.cascade_slot;
 70        let style = self.hovered.get().then_some(self.hovered_style.clone());
 71        self.style_cascade().set(slot, style);
 72
 73        let hovered = self.hovered.clone();
 74        cx.on_event(layout.order, move |_view, _: &MouseMovedEvent, cx| {
 75            cx.bubble_event();
 76            if bounds.contains_point(cx.mouse_position()) != hovered.get() {
 77                cx.repaint();
 78            }
 79        });
 80
 81        self.child
 82            .paint(view, parent_origin, layout, paint_state, cx);
 83    }
 84}
 85
 86impl<E: Styleable<Style = Style>> StyleHelpers for Hoverable<E> {}
 87
 88impl<V: 'static, E: Interactive<V> + Styleable> Interactive<V> for Hoverable<E> {
 89    fn interaction_handlers(&mut self) -> &mut InteractionHandlers<V> {
 90        self.child.interaction_handlers()
 91    }
 92}
 93
 94impl<V: 'static, E: ParentElement<V> + Styleable> ParentElement<V> for Hoverable<E> {
 95    fn children_mut(&mut self) -> &mut SmallVec<[AnyElement<V>; 2]> {
 96        self.child.children_mut()
 97    }
 98}
 99
100impl<V: 'static, E: Element<V> + Styleable> IntoElement<V> for Hoverable<E> {
101    type Element = Self;
102
103    fn into_element(self) -> Self::Element {
104        self
105    }
106}