zed/crates/editor/src/test.rs

use gpui::{Entity, ModelHandle};
use smol::channel;
use std::marker::PhantomData;

pub fn sample_text(rows: usize, cols: usize) -> String {
    let mut text = String::new();
    for row in 0..rows {
        let c: char = ('a' as u32 + row as u32) as u8 as char;
        let mut line = c.to_string().repeat(cols);
        if row < rows - 1 {
            line.push('\n');
        }
        text += &line;
    }
    text
}

pub struct Observer<T>(PhantomData<T>);

impl<T: 'static> Entity for Observer<T> {
    type Event = ();
}

impl<T: Entity> Observer<T> {
    pub fn new(
        handle: &ModelHandle<T>,
        cx: &mut gpui::TestAppContext,
    ) -> (ModelHandle<Self>, channel::Receiver<()>) {
        let (notify_tx, notify_rx) = channel::unbounded();
        let observer = cx.add_model(|cx| {
            cx.observe(handle, move |_, _, _| {
                let _ = notify_tx.try_send(());
            })
            .detach();
            Observer(PhantomData)
        });
        (observer, notify_rx)
    }
}