Xilem: the Linebender rewrite

use book_error::Result;
use xilem::view::{flex_col, label, text_button};
use xilem::{EventLoop, WidgetView, WindowOptions, Xilem};

struct AppState {
    count: i32,
}

// A pure function from state to a view description. Xilem diffs the
// descriptions and updates the retained widgets (Masonry) underneath.
fn app_logic(state: &mut AppState) -> impl WidgetView<AppState> + use<> {
    flex_col((
        label(format!("count: {}", state.count)),
        text_button("increment", |state: &mut AppState| state.count += 1),
    ))
}

fn main() -> Result<()> {
    let app = Xilem::new_simple(AppState { count: 0 }, app_logic, WindowOptions::new("Counter"));
    app.run_in(EventLoop::with_user_event())?;
    Ok(())
}

use book_error::Result;
use xilem::core::lens;
use xilem::view::{flex_row, label, text_button};
use xilem::{EventLoop, WidgetView, WindowOptions, Xilem};

#[derive(Default)]
struct AppState {
    likes: u32,
    dislikes: u32,
}

// A reusable component that only knows about the slice of state it edits.
fn votes(n: &mut u32) -> impl WidgetView<u32> + use<> {
    flex_row((label(format!("votes: {n}")), text_button("+", |n: &mut u32| *n += 1)))
}

// `lens` focuses the component on one field, like Druid's Lens did.
fn app_logic(_state: &mut AppState) -> impl WidgetView<AppState> + use<> {
    flex_row((
        lens(votes, |s: &mut AppState| &mut s.likes),
        lens(votes, |s: &mut AppState| &mut s.dislikes),
    ))
}

fn main() -> Result<()> {
    Xilem::new_simple(AppState::default(), app_logic, WindowOptions::new("Votes"))
        .run_in(EventLoop::with_user_event())?;
    Ok(())
}