428 lines
12 KiB
Rust
428 lines
12 KiB
Rust
//! Listen to external events in your application.
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mod tracker;
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pub use tracker::Tracker;
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use crate::core::event::{self, Event};
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use crate::core::Hasher;
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use crate::futures::{Future, Stream};
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use crate::{BoxStream, MaybeSend};
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use futures::channel::mpsc;
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use futures::never::Never;
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use std::any::TypeId;
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use std::hash::Hash;
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/// A stream of runtime events.
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///
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/// It is the input of a [`Subscription`].
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pub type EventStream = BoxStream<(Event, event::Status)>;
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/// A request to listen to external events.
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///
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/// Besides performing async actions on demand with `Command`, most
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/// applications also need to listen to external events passively.
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///
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/// A [`Subscription`] is normally provided to some runtime, like a `Command`,
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/// and it will generate events as long as the user keeps requesting it.
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///
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/// For instance, you can use a [`Subscription`] to listen to a `WebSocket`
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/// connection, keyboard presses, mouse events, time ticks, etc.
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#[must_use = "`Subscription` must be returned to runtime to take effect"]
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pub struct Subscription<Message> {
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recipes: Vec<Box<dyn Recipe<Output = Message>>>,
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}
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impl<Message> Subscription<Message> {
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/// Returns an empty [`Subscription`] that will not produce any output.
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pub fn none() -> Self {
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Self {
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recipes: Vec::new(),
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}
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}
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/// Creates a [`Subscription`] from a [`Recipe`] describing it.
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pub fn from_recipe(
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recipe: impl Recipe<Output = Message> + 'static,
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) -> Self {
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Self {
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recipes: vec![Box::new(recipe)],
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}
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}
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/// Batches all the provided subscriptions and returns the resulting
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/// [`Subscription`].
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pub fn batch(
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subscriptions: impl IntoIterator<Item = Subscription<Message>>,
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) -> Self {
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Self {
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recipes: subscriptions
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.into_iter()
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.flat_map(|subscription| subscription.recipes)
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.collect(),
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}
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}
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/// Returns the different recipes of the [`Subscription`].
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pub fn into_recipes(self) -> Vec<Box<dyn Recipe<Output = Message>>> {
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self.recipes
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}
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/// Adds a value to the [`Subscription`] context.
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///
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/// The value will be part of the identity of a [`Subscription`].
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pub fn with<T>(mut self, value: T) -> Subscription<(T, Message)>
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where
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Message: 'static,
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T: std::hash::Hash + Clone + Send + Sync + 'static,
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{
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Subscription {
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recipes: self
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.recipes
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.drain(..)
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.map(|recipe| {
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Box::new(With::new(recipe, value.clone()))
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as Box<dyn Recipe<Output = (T, Message)>>
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})
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.collect(),
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}
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}
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/// Transforms the [`Subscription`] output with the given function.
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pub fn map<A>(
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mut self,
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f: impl Fn(Message) -> A + MaybeSend + Clone + 'static,
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) -> Subscription<A>
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where
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Message: 'static,
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A: 'static,
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{
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Subscription {
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recipes: self
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.recipes
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.drain(..)
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.map(move |recipe| {
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Box::new(Map::new(recipe, f.clone()))
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as Box<dyn Recipe<Output = A>>
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})
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.collect(),
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}
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}
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}
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impl<Message> std::fmt::Debug for Subscription<Message> {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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f.debug_struct("Subscription").finish()
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}
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}
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/// The description of a [`Subscription`].
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///
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/// A [`Recipe`] is the internal definition of a [`Subscription`]. It is used
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/// by runtimes to run and identify subscriptions. You can use it to create your
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/// own!
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///
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/// # Examples
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/// The repository has a couple of [examples] that use a custom [`Recipe`]:
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///
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/// - [`download_progress`], a basic application that asynchronously downloads
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/// a dummy file of 100 MB and tracks the download progress.
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/// - [`stopwatch`], a watch with start/stop and reset buttons showcasing how
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/// to listen to time.
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///
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/// [examples]: https://github.com/iced-rs/iced/tree/0.10/examples
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/// [`download_progress`]: https://github.com/iced-rs/iced/tree/0.10/examples/download_progress
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/// [`stopwatch`]: https://github.com/iced-rs/iced/tree/0.10/examples/stopwatch
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pub trait Recipe {
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/// The events that will be produced by a [`Subscription`] with this
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/// [`Recipe`].
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type Output;
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/// Hashes the [`Recipe`].
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///
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/// This is used by runtimes to uniquely identify a [`Subscription`].
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fn hash(&self, state: &mut Hasher);
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/// Executes the [`Recipe`] and produces the stream of events of its
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/// [`Subscription`].
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fn stream(self: Box<Self>, input: EventStream) -> BoxStream<Self::Output>;
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}
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struct Map<A, B, F>
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where
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F: Fn(A) -> B + 'static,
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{
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id: TypeId,
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recipe: Box<dyn Recipe<Output = A>>,
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mapper: F,
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}
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impl<A, B, F> Map<A, B, F>
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where
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F: Fn(A) -> B + 'static,
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{
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fn new(recipe: Box<dyn Recipe<Output = A>>, mapper: F) -> Self {
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Map {
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id: TypeId::of::<F>(),
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recipe,
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mapper,
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}
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}
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}
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impl<A, B, F> Recipe for Map<A, B, F>
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where
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A: 'static,
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B: 'static,
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F: Fn(A) -> B + 'static + MaybeSend,
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{
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type Output = B;
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fn hash(&self, state: &mut Hasher) {
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self.id.hash(state);
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self.recipe.hash(state);
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}
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fn stream(self: Box<Self>, input: EventStream) -> BoxStream<Self::Output> {
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use futures::StreamExt;
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let mapper = self.mapper;
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Box::pin(self.recipe.stream(input).map(mapper))
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}
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}
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struct With<A, B> {
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recipe: Box<dyn Recipe<Output = A>>,
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value: B,
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}
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impl<A, B> With<A, B> {
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fn new(recipe: Box<dyn Recipe<Output = A>>, value: B) -> Self {
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With { recipe, value }
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}
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}
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impl<A, B> Recipe for With<A, B>
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where
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A: 'static,
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B: 'static + std::hash::Hash + Clone + Send + Sync,
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{
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type Output = (B, A);
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fn hash(&self, state: &mut Hasher) {
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std::any::TypeId::of::<B>().hash(state);
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self.value.hash(state);
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self.recipe.hash(state);
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}
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fn stream(self: Box<Self>, input: EventStream) -> BoxStream<Self::Output> {
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use futures::StreamExt;
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let value = self.value;
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Box::pin(
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self.recipe
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.stream(input)
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.map(move |element| (value.clone(), element)),
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)
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}
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}
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/// Returns a [`Subscription`] that will call the given function to create and
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/// asynchronously run the given [`Stream`].
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pub fn run<S, Message>(builder: fn() -> S) -> Subscription<Message>
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where
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S: Stream<Item = Message> + MaybeSend + 'static,
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Message: 'static,
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{
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Subscription::from_recipe(Runner {
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id: builder,
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spawn: move |_| builder(),
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})
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}
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/// Returns a [`Subscription`] that will create and asynchronously run the
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/// given [`Stream`].
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///
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/// The `id` will be used to uniquely identify the [`Subscription`].
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pub fn run_with_id<I, S, Message>(id: I, stream: S) -> Subscription<Message>
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where
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I: Hash + 'static,
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S: Stream<Item = Message> + MaybeSend + 'static,
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Message: 'static,
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{
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Subscription::from_recipe(Runner {
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id,
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spawn: move |_| stream,
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})
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}
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/// Returns a [`Subscription`] that will create and asynchronously run a
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/// [`Stream`] that will call the provided closure to produce every `Message`.
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///
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/// The `id` will be used to uniquely identify the [`Subscription`].
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pub fn unfold<I, T, Fut, Message>(
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id: I,
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initial: T,
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mut f: impl FnMut(T) -> Fut + MaybeSend + Sync + 'static,
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) -> Subscription<Message>
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where
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I: Hash + 'static,
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T: MaybeSend + 'static,
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Fut: Future<Output = (Message, T)> + MaybeSend + 'static,
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Message: 'static + MaybeSend,
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{
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use futures::future::FutureExt;
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run_with_id(
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id,
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futures::stream::unfold(initial, move |state| f(state).map(Some)),
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)
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}
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pub(crate) fn filter_map<I, F, Message>(id: I, f: F) -> Subscription<Message>
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where
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I: Hash + 'static,
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F: Fn(Event, event::Status) -> Option<Message> + MaybeSend + 'static,
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Message: 'static + MaybeSend,
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{
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Subscription::from_recipe(Runner {
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id,
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spawn: |events| {
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use futures::future;
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use futures::stream::StreamExt;
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events.filter_map(move |(event, status)| {
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future::ready(f(event, status))
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})
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},
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})
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}
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/// Creates a [`Subscription`] that publishes the events sent from a [`Future`]
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/// to an [`mpsc::Sender`] with the given bounds.
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///
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/// # Creating an asynchronous worker with bidirectional communication
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/// You can leverage this helper to create a [`Subscription`] that spawns
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/// an asynchronous worker in the background and establish a channel of
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/// communication with an `iced` application.
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///
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/// You can achieve this by creating an `mpsc` channel inside the closure
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/// and returning the `Sender` as a `Message` for the `Application`:
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///
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/// ```
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/// use iced_futures::subscription::{self, Subscription};
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/// use iced_futures::futures::channel::mpsc;
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/// use iced_futures::futures::sink::SinkExt;
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///
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/// pub enum Event {
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/// Ready(mpsc::Sender<Input>),
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/// WorkFinished,
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/// // ...
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/// }
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///
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/// enum Input {
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/// DoSomeWork,
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/// // ...
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/// }
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///
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/// enum State {
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/// Starting,
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/// Ready(mpsc::Receiver<Input>),
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/// }
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///
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/// fn some_worker() -> Subscription<Event> {
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/// struct SomeWorker;
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///
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/// subscription::channel(std::any::TypeId::of::<SomeWorker>(), 100, |mut output| async move {
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/// let mut state = State::Starting;
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///
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/// loop {
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/// match &mut state {
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/// State::Starting => {
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/// // Create channel
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/// let (sender, receiver) = mpsc::channel(100);
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///
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/// // Send the sender back to the application
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/// output.send(Event::Ready(sender)).await;
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///
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/// // We are ready to receive messages
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/// state = State::Ready(receiver);
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/// }
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/// State::Ready(receiver) => {
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/// use iced_futures::futures::StreamExt;
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///
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/// // Read next input sent from `Application`
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/// let input = receiver.select_next_some().await;
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///
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/// match input {
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/// Input::DoSomeWork => {
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/// // Do some async work...
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///
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/// // Finally, we can optionally produce a message to tell the
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/// // `Application` the work is done
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/// output.send(Event::WorkFinished).await;
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/// }
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/// }
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/// }
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/// }
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/// }
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/// })
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/// }
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/// ```
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///
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/// Check out the [`websocket`] example, which showcases this pattern to maintain a `WebSocket`
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/// connection open.
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///
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/// [`websocket`]: https://github.com/iced-rs/iced/tree/0.10/examples/websocket
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pub fn channel<I, Fut, Message>(
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id: I,
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size: usize,
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f: impl FnOnce(mpsc::Sender<Message>) -> Fut + MaybeSend + 'static,
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) -> Subscription<Message>
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where
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I: Hash + 'static,
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Fut: Future<Output = Never> + MaybeSend + 'static,
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Message: 'static + MaybeSend,
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{
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use futures::stream::{self, StreamExt};
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Subscription::from_recipe(Runner {
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id,
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spawn: move |_| {
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let (sender, receiver) = mpsc::channel(size);
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let runner = stream::once(f(sender)).map(|_| unreachable!());
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stream::select(receiver, runner)
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},
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})
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}
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struct Runner<I, F, S, Message>
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where
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F: FnOnce(EventStream) -> S,
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S: Stream<Item = Message>,
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{
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id: I,
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spawn: F,
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}
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impl<I, S, F, Message> Recipe for Runner<I, F, S, Message>
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where
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I: Hash + 'static,
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F: FnOnce(EventStream) -> S,
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S: Stream<Item = Message> + MaybeSend + 'static,
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{
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type Output = Message;
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fn hash(&self, state: &mut Hasher) {
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std::any::TypeId::of::<I>().hash(state);
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self.id.hash(state);
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}
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fn stream(self: Box<Self>, input: EventStream) -> BoxStream<Self::Output> {
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crate::boxed_stream((self.spawn)(input))
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}
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}
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