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use crate::widget::prelude::*;
use crate::{Data, Point, WidgetPod};
use tracing::instrument;
type ChildPicker<T, U> = dyn Fn(&T, &Env) -> U;
type ChildBuilder<T, U> = dyn Fn(&U, &T, &Env) -> Box<dyn Widget<T>>;
pub struct ViewSwitcher<T, U> {
child_picker: Box<ChildPicker<T, U>>,
child_builder: Box<ChildBuilder<T, U>>,
active_child: Option<WidgetPod<T, Box<dyn Widget<T>>>>,
active_child_id: Option<U>,
}
impl<T: Data, U: Data> ViewSwitcher<T, U> {
pub fn new(
child_picker: impl Fn(&T, &Env) -> U + 'static,
child_builder: impl Fn(&U, &T, &Env) -> Box<dyn Widget<T>> + 'static,
) -> Self {
Self {
child_picker: Box::new(child_picker),
child_builder: Box::new(child_builder),
active_child: None,
active_child_id: None,
}
}
}
impl<T: Data, U: Data> Widget<T> for ViewSwitcher<T, U> {
#[instrument(
name = "ViewSwitcher",
level = "trace",
skip(self, ctx, event, data, env)
)]
fn event(&mut self, ctx: &mut EventCtx, event: &Event, data: &mut T, env: &Env) {
if let Some(child) = self.active_child.as_mut() {
child.event(ctx, event, data, env);
}
}
#[instrument(
name = "ViewSwitcher",
level = "trace",
skip(self, ctx, event, data, env)
)]
fn lifecycle(&mut self, ctx: &mut LifeCycleCtx, event: &LifeCycle, data: &T, env: &Env) {
if let LifeCycle::WidgetAdded = event {
let child_id = (self.child_picker)(data, env);
self.active_child = Some(WidgetPod::new((self.child_builder)(&child_id, data, env)));
self.active_child_id = Some(child_id);
}
if let Some(child) = self.active_child.as_mut() {
child.lifecycle(ctx, event, data, env);
}
}
#[instrument(
name = "ViewSwitcher",
level = "trace",
skip(self, ctx, _old_data, data, env)
)]
fn update(&mut self, ctx: &mut UpdateCtx, _old_data: &T, data: &T, env: &Env) {
let child_id = (self.child_picker)(data, env);
if !child_id.same(self.active_child_id.as_ref().unwrap()) {
self.active_child = Some(WidgetPod::new((self.child_builder)(&child_id, data, env)));
self.active_child_id = Some(child_id);
ctx.children_changed();
} else if let Some(child) = self.active_child.as_mut() {
child.update(ctx, data, env);
}
}
#[instrument(name = "ViewSwitcher", level = "trace", skip(self, ctx, bc, data, env))]
fn layout(&mut self, ctx: &mut LayoutCtx, bc: &BoxConstraints, data: &T, env: &Env) -> Size {
match self.active_child {
Some(ref mut child) => {
let size = child.layout(ctx, bc, data, env);
child.set_origin(ctx, Point::ORIGIN);
size
}
None => bc.max(),
}
}
#[instrument(name = "ViewSwitcher", level = "trace", skip(self, ctx, data, env))]
fn paint(&mut self, ctx: &mut PaintCtx, data: &T, env: &Env) {
if let Some(ref mut child) = self.active_child {
child.paint_raw(ctx, data, env);
}
}
}