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//! Build interactive cross-platform applications.
use crate::{Command, Element, Executor, Settings, Subscription};
pub use crate::style::application::{Appearance, StyleSheet};
/// An interactive cross-platform application.
///
/// This trait is the main entrypoint of Iced. Once implemented, you can run
/// your GUI application by simply calling [`run`](#method.run).
///
/// - On native platforms, it will run in its own window.
/// - On the web, it will take control of the `<title>` and the `<body>` of the
/// document.
///
/// An [`Application`] can execute asynchronous actions by returning a
/// [`Command`] in some of its methods. If you do not intend to perform any
/// background work in your program, the [`Sandbox`] trait offers a simplified
/// interface.
///
/// When using an [`Application`] with the `debug` feature enabled, a debug view
/// can be toggled by pressing `F12`.
///
/// # Examples
/// [The repository has a bunch of examples] that use the [`Application`] trait:
///
/// - [`clock`], an application that uses the [`Canvas`] widget to draw a clock
/// and its hands to display the current time.
/// - [`download_progress`], a basic application that asynchronously downloads
/// a dummy file of 100 MB and tracks the download progress.
/// - [`events`], a log of native events displayed using a conditional
/// [`Subscription`].
/// - [`game_of_life`], an interactive version of the [Game of Life], invented
/// by [John Horton Conway].
/// - [`pokedex`], an application that displays a random Pokédex entry (sprite
/// included!) by using the [PokéAPI].
/// - [`solar_system`], an animated solar system drawn using the [`Canvas`] widget
/// and showcasing how to compose different transforms.
/// - [`stopwatch`], a watch with start/stop and reset buttons showcasing how
/// to listen to time.
/// - [`todos`], a todos tracker inspired by [TodoMVC].
///
/// [The repository has a bunch of examples]: https://github.com/iced-rs/iced/tree/0.12/examples
/// [`clock`]: https://github.com/iced-rs/iced/tree/0.12/examples/clock
/// [`download_progress`]: https://github.com/iced-rs/iced/tree/0.12/examples/download_progress
/// [`events`]: https://github.com/iced-rs/iced/tree/0.12/examples/events
/// [`game_of_life`]: https://github.com/iced-rs/iced/tree/0.12/examples/game_of_life
/// [`pokedex`]: https://github.com/iced-rs/iced/tree/0.12/examples/pokedex
/// [`solar_system`]: https://github.com/iced-rs/iced/tree/0.12/examples/solar_system
/// [`stopwatch`]: https://github.com/iced-rs/iced/tree/0.12/examples/stopwatch
/// [`todos`]: https://github.com/iced-rs/iced/tree/0.12/examples/todos
/// [`Sandbox`]: crate::Sandbox
/// [`Canvas`]: crate::widget::Canvas
/// [PokéAPI]: https://pokeapi.co/
/// [TodoMVC]: http://todomvc.com/
///
/// ## A simple "Hello, world!"
///
/// If you just want to get started, here is a simple [`Application`] that
/// says "Hello, world!":
///
/// ```no_run
/// use iced::executor;
/// use iced::{Application, Command, Element, Settings, Theme};
///
/// pub fn main() -> iced::Result {
/// Hello::run(Settings::default())
/// }
///
/// struct Hello;
///
/// impl Application for Hello {
/// type Executor = executor::Default;
/// type Flags = ();
/// type Message = ();
/// type Theme = Theme;
///
/// fn new(_flags: ()) -> (Hello, Command<Self::Message>) {
/// (Hello, Command::none())
/// }
///
/// fn title(&self) -> String {
/// String::from("A cool application")
/// }
///
/// fn update(&mut self, _message: Self::Message) -> Command<Self::Message> {
/// Command::none()
/// }
///
/// fn view(&self) -> Element<Self::Message> {
/// "Hello, world!".into()
/// }
/// }
/// ```
pub trait Application: Sized {
/// The [`Executor`] that will run commands and subscriptions.
///
/// The [default executor] can be a good starting point!
///
/// [`Executor`]: Self::Executor
/// [default executor]: crate::executor::Default
type Executor: Executor;
/// The type of __messages__ your [`Application`] will produce.
type Message: std::fmt::Debug + Send;
/// The theme of your [`Application`].
type Theme: Default + StyleSheet;
/// The data needed to initialize your [`Application`].
type Flags;
/// Initializes the [`Application`] with the flags provided to
/// [`run`] as part of the [`Settings`].
///
/// Here is where you should return the initial state of your app.
///
/// Additionally, you can return a [`Command`] if you need to perform some
/// async action in the background on startup. This is useful if you want to
/// load state from a file, perform an initial HTTP request, etc.
///
/// [`run`]: Self::run
fn new(flags: Self::Flags) -> (Self, Command<Self::Message>);
/// Returns the current title of the [`Application`].
///
/// This title can be dynamic! The runtime will automatically update the
/// title of your application when necessary.
fn title(&self) -> String;
/// Handles a __message__ and updates the state of the [`Application`].
///
/// This is where you define your __update logic__. All the __messages__,
/// produced by either user interactions or commands, will be handled by
/// this method.
///
/// Any [`Command`] returned will be executed immediately in the background.
fn update(&mut self, message: Self::Message) -> Command<Self::Message>;
/// Returns the widgets to display in the [`Application`].
///
/// These widgets can produce __messages__ based on user interaction.
fn view(&self) -> Element<'_, Self::Message, Self::Theme, crate::Renderer>;
/// Returns the current [`Theme`] of the [`Application`].
///
/// [`Theme`]: Self::Theme
fn theme(&self) -> Self::Theme {
Self::Theme::default()
}
/// Returns the current `Style` of the [`Theme`].
///
/// [`Theme`]: Self::Theme
fn style(&self) -> <Self::Theme as StyleSheet>::Style {
<Self::Theme as StyleSheet>::Style::default()
}
/// Returns the event [`Subscription`] for the current state of the
/// application.
///
/// A [`Subscription`] will be kept alive as long as you keep returning it,
/// and the __messages__ produced will be handled by
/// [`update`](#tymethod.update).
///
/// By default, this method returns an empty [`Subscription`].
fn subscription(&self) -> Subscription<Self::Message> {
Subscription::none()
}
/// Returns the scale factor of the [`Application`].
///
/// It can be used to dynamically control the size of the UI at runtime
/// (i.e. zooming).
///
/// For instance, a scale factor of `2.0` will make widgets twice as big,
/// while a scale factor of `0.5` will shrink them to half their size.
///
/// By default, it returns `1.0`.
fn scale_factor(&self) -> f64 {
1.0
}
/// Runs the [`Application`].
///
/// On native platforms, this method will take control of the current thread
/// until the [`Application`] exits.
///
/// On the web platform, this method __will NOT return__ unless there is an
/// [`Error`] during startup.
///
/// [`Error`]: crate::Error
fn run(settings: Settings<Self::Flags>) -> crate::Result
where
Self: 'static,
{
#[allow(clippy::needless_update)]
let renderer_settings = crate::renderer::Settings {
default_font: settings.default_font,
default_text_size: settings.default_text_size,
antialiasing: if settings.antialiasing {
Some(crate::graphics::Antialiasing::MSAAx4)
} else {
None
},
..crate::renderer::Settings::default()
};
Ok(crate::shell::application::run::<
Instance<Self>,
Self::Executor,
crate::renderer::Compositor,
>(settings.into(), renderer_settings)?)
}
}
struct Instance<A: Application>(A);
impl<A> crate::runtime::Program for Instance<A>
where
A: Application,
{
type Message = A::Message;
type Theme = A::Theme;
type Renderer = crate::Renderer;
fn update(&mut self, message: Self::Message) -> Command<Self::Message> {
self.0.update(message)
}
fn view(&self) -> Element<'_, Self::Message, Self::Theme, Self::Renderer> {
self.0.view()
}
}
impl<A> crate::shell::Application for Instance<A>
where
A: Application,
{
type Flags = A::Flags;
fn new(flags: Self::Flags) -> (Self, Command<A::Message>) {
let (app, command) = A::new(flags);
(Instance(app), command)
}
fn title(&self) -> String {
self.0.title()
}
fn theme(&self) -> A::Theme {
self.0.theme()
}
fn style(&self) -> <A::Theme as StyleSheet>::Style {
self.0.style()
}
fn subscription(&self) -> Subscription<Self::Message> {
self.0.subscription()
}
fn scale_factor(&self) -> f64 {
self.0.scale_factor()
}
}