Slow UI Render

[wanglunhui2012]

Bug Description

I wan't to display http request result, but ui become very slow.

Reproducible Code (if applicable)

export component AppWindow inherits Window {
    in-out property <string> url: "https://github.com/slint-ui/slint/issues/747";
    in-out property <string> method: "GET";
    in-out property <string> header: "";
    in-out property <string> body: "";
    in-out property <string> response: "";
    callback send_request();
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    let ui = AppWindow::new()?;

    ui.on_send_request({
        let ui_handle = ui.as_weak();
        move || {
            let ui = ui_handle.unwrap();

            let url = ui.get_url();
            let method = ui.get_method();
            let header = ui.get_header();
            let body = ui.get_body();

            let response_display = ui.as_weak();
            tokio::spawn(async move {
                let client = Client::new();

            let mut request = match method.as_str() {
                "GET" => client.get(url.as_str()),
                "POST" => client.post(url.as_str()),
                _ => return,
            };

            if method == "POST" && !body.is_empty() {
                request = request.body(body);
            }
            let response = request.send().await;
                if let Ok(res) = response {
                    let status = res.status().to_string();
                    let headers = res
                        .headers()
                        .iter()
                        .map(|(k, v)| format!("{}: {}", k, v.to_str().unwrap_or_default()))
                        .collect::<Vec<_>>()
                        .join("\n");
                    let body = res.text().await.unwrap_or_default();

                    let result = format!("Status: {}\n\nHeaders:\n{}\n\nBody:\n{}", status, headers, body);
                    println!("{result}");
                    slint::invoke_from_event_loop(move || {
                        println!("1");
                        response_display.unwrap().set_response(SharedString::from(body));
                        println!("2");
                    });
                    println!("3");
                } else {
                    response_display.upgrade_in_event_loop(move |handle| {
                        handle.set_response(SharedString::from("Request Failed"));
                    });
                }
}
    });

    ui.run()?;

    Ok(())
}

Environment Details

• Slint Version: 1.8.0
• Platform/OS: MacOS Arm64
• Programming Language: Rust
• Backend/Renderer: Default

Product Impact

No response

[tronical]

I suspect that your main thread ends up hanging if Tokio doesn't hand off the task to a thread. Could you try to apply the workaround mentioned at the bottom of this page to see if that fixes it?

https://docs.slint.dev/latest/docs/rust/slint/fn.spawn_local#compatibility-with-tokio-and-other-runtimes

[wanglunhui2012]

I suspect that your main thread ends up hanging if Tokio doesn't hand off the task to a thread. Could you try to apply the workaround mentioned at the bottom of this page to see if that fixes it?

https://docs.slint.dev/latest/docs/rust/slint/fn.spawn_local#compatibility-with-tokio-and-other-runtimes

But when I replace response_display.unwrap().set_response(SharedString::from(body)); to response_display.unwrap().set_response(SharedString::from("success"));, it work well. I think it is because the response is too long.

[ogoffart]

How big is the response?
is it measured in kB or in MB?
In your code i see you print "1" and "2" and things like that. At what point does it slow down.
I see that you also print the body to the console. That could also be the slow part.