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use crate::{Bus, Color, Css, Widget};
use dodrio::bumpalo;
use std::rc::Rc;
/// A generic [`Widget`].
///
/// It is useful to build composable user interfaces that do not leak
/// implementation details in their __view logic__.
///
/// If you have a [built-in widget], you should be able to use `Into<Element>`
/// to turn it into an [`Element`].
///
/// [built-in widget]: widget/index.html
/// [`Widget`]: widget/trait.Widget.html
/// [`Element`]: struct.Element.html
#[allow(missing_debug_implementations)]
pub struct Element<'a, Message> {
pub(crate) widget: Box<dyn Widget<Message> + 'a>,
}
impl<'a, Message> Element<'a, Message> {
/// Create a new [`Element`] containing the given [`Widget`].
///
/// [`Element`]: struct.Element.html
/// [`Widget`]: widget/trait.Widget.html
pub fn new(widget: impl Widget<Message> + 'a) -> Self {
Self {
widget: Box::new(widget),
}
}
/// Applies a transformation to the produced message of the [`Element`].
///
/// This method is useful when you want to decouple different parts of your
/// UI and make them __composable__.
///
/// [`Element`]: struct.Element.html
pub fn map<F, B>(self, f: F) -> Element<'a, B>
where
Message: 'static,
B: 'static,
F: 'static + Fn(Message) -> B,
{
Element {
widget: Box::new(Map::new(self.widget, f)),
}
}
/// Marks the [`Element`] as _to-be-explained_.
pub fn explain(self, _color: Color) -> Element<'a, Message> {
self
}
/// Produces a VDOM node for the [`Element`].
pub fn node<'b>(
&self,
bump: &'b bumpalo::Bump,
bus: &Bus<Message>,
style_sheet: &mut Css<'b>,
) -> dodrio::Node<'b> {
self.widget.node(bump, bus, style_sheet)
}
}
struct Map<'a, A, B> {
widget: Box<dyn Widget<A> + 'a>,
mapper: Rc<Box<dyn Fn(A) -> B>>,
}
impl<'a, A, B> Map<'a, A, B> {
pub fn new<F>(widget: Box<dyn Widget<A> + 'a>, mapper: F) -> Map<'a, A, B>
where
F: 'static + Fn(A) -> B,
{
Map {
widget,
mapper: Rc::new(Box::new(mapper)),
}
}
}
impl<'a, A, B> Widget<B> for Map<'a, A, B>
where
A: 'static,
B: 'static,
{
fn node<'b>(
&self,
bump: &'b bumpalo::Bump,
bus: &Bus<B>,
style_sheet: &mut Css<'b>,
) -> dodrio::Node<'b> {
self.widget
.node(bump, &bus.map(self.mapper.clone()), style_sheet)
}
}
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