Program API

[hecrj]

This PR introduces a new Program API as a more convenient—although less powerful—alternative to the Sandbox and Application traits.

The main motivation is lowering the learning curve and entry barrier of the library. Specifically, Application has a lot of moving parts (e.g. Flags, Executor, Theme, subscription, etc.)

The run Function

There is a new run function in the root module that can be used to easily run basic applications, like the classic counter:

use iced::widget::{button, column, text, Column};

pub fn main() -> iced::Result {
    iced::run("A counter", update, view)
}

#[derive(Debug, Clone)]
enum Message {
    Increment,
}

fn update(value: &mut u64, message: Message) {
    match message {
        Message::Increment => *value += 1,
    }
}

fn view(value: &u64) -> Column<Message> {
    column![
        text(value),
        button("+").on_press(Message::Increment),
    ]
}

The Program API

The Program API can be used to create and run iced applications step by step—without coupling your logic to a trait or a specific type.

For instance, here is the new main function of the clock example:

pub fn main() -> iced::Result {
    iced::sandbox("Clock - Iced", Clock::update, Clock::view)
        .subscription(Clock::subscription)
        .theme(Clock::theme)
        .antialiased()
        .run()
}