use std::fmt::Debug;
use figures::Size;
use crate::context::LayoutContext;
use crate::value::{Dynamic, DynamicReader, IntoDynamic, IntoReader, Source};
use crate::widget::{WidgetInstance, WidgetRef, WrapperWidget};
use crate::ConstraintLimit;
#[derive(Debug)]
pub struct Switcher {
source: DynamicReader<WidgetInstance>,
child: WidgetRef,
}
impl Switcher {
pub fn mapping<T, F>(source: impl IntoDynamic<T>, mut map: F) -> Self
where
F: FnMut(&T, &Dynamic<T>) -> WidgetInstance + Send + 'static,
T: Send + 'static,
{
let source = source.into_dynamic();
Self::new(source.clone().map_each(move |value| map(value, &source)))
}
#[must_use]
pub fn new(source: impl IntoReader<WidgetInstance>) -> Self {
let source = source.into_reader();
let child = WidgetRef::new(source.get());
Self { source, child }
}
}
impl WrapperWidget for Switcher {
fn child_mut(&mut self) -> &mut WidgetRef {
&mut self.child
}
fn adjust_child_constraints(
&mut self,
available_space: Size<ConstraintLimit>,
context: &mut LayoutContext<'_, '_, '_, '_>,
) -> Size<ConstraintLimit> {
if self.source.has_updated() {
self.child.unmount_in(context);
self.child = WidgetRef::new(self.source.get());
}
context.invalidate_when_changed(&self.source);
available_space
}
}