If you're reading this, you have probably found yourself on Hacker News once or twice. It's a simple, beloved site where users share tech-related links and always1 have civil discussions about them. But the UX is dated, and it is not so enjoyable to browse via the official website.
I am far from the first person to come to this conclusion, as there are literally thousands of HN clients out there. But I took this opportunity to explore cross-platform graphical application development in Rust, and resolved to write my own client.
The Rust community has been asking itself for a while now, Are we GUI yet?"and at this point, the answer is decidedly YES. I decided to go with egui: an opinionated, declarative, immediate-mode GUI library with backends for both web and native.
The Hacker News website is impressive in this day and age, in that it still runs on a single, on-prem server and has a very simple architecture. But the official Hacker News API is not great, and is "essentially a dump of [their] in-memory data structures"— making certain common actions (like listing entities) quite cumbersome. You cannot fetch a list of posts; instead, you fetch a list of post IDs, then fetch each post in separate requests. Same goes for comments and other entities.
This led me to implement a super-parallelized client that uses an absurd number of threads (one per entity) to hydrate the UI concurrently and efficiently, all at 60FPS.
impl YReader {
fn init(&self) {
let data_top = Arc::clone(&self.data);
thread::spawn(move || loop {
let client = JsonClient::new();
let ids = client.top_stories();
if let Ok(ids) = ids {
let page;
{
let data = data_top.lock().unwrap();
page = data.top_page;
}
for (idx, id) in ids.iter().take(WINDOW * (page + 1)).enumerate() {
if let Ok(item) = client.item(*id) {
let mut data = data_top.lock().unwrap();
data.top.insert(idx, item);
}
}
let mut data = data_top.lock().unwrap();
data.top_ids = ids;
data.top_page = (data.top_page + 1) % 2;
}
thread::sleep(Duration::from_secs(REFETCH_DELAY_SECONDS));
});
let data_new = Arc::clone(&self.data);
thread::spawn(move || loop {
let client = JsonClient::new();
let ids = client.new_stories();
if let Ok(ids) = ids {
let page;
{
let data = data_new.lock().unwrap();
page = data.new_page;
}
for (idx, id) in ids.iter().take(WINDOW * (page + 1)).enumerate() {
if let Ok(item) = client.item(*id) {
let mut data = data_new.lock().unwrap();
data.new.insert(idx, item);
}
}
let mut data = data_new.lock().unwrap();
data.new_ids = ids;
data.new_page = (data.new_page + 1) % 2;
}
thread::sleep(Duration::from_secs(REFETCH_DELAY_SECONDS));
});
}
}While the client is already a great way to browse the content, I have yet to implement a few features before considering this project ready for public consumption: