How to update the value of ProgressIndicator in a child thread?

[LeeeSe]

I'm trying to make a progress bar for my program and I need to put the task of updating the progress bar in a subthread, but I can't pass the ui into the subthread, is this the right way for me to implement my idea? Or is there a more standard way of doing it?

use dali::{choose_video_file, compress_video};
use slint::SharedString;

slint::include_modules!();

fn main() -> Result<(), slint::PlatformError> {
    let ui = AppWindow::new()?;
    let ui_handle = ui.as_weak();

    ui.on_choose_video_file({
        let ui = ui_handle.unwrap();
        move || {
            let input = choose_video_file();
            if !input.is_none() {
                ui.set_compress_enabled(true);
                ui.set_compress_video_input_file_path(SharedString::from(
                    input.unwrap().to_str().unwrap(),
                ));
            }
        }
    });

    ui.on_compress_video({
        let ui = ui_handle.unwrap();
        move || {
            let (tx, rx) = std::sync::mpsc::channel::<f32>();
            let input = ui.get_compress_video_input_file_path().clone();
            let input = std::path::Path::new(input.as_str());
            let video_type = "mp4";
            compress_video(input, video_type, tx);

            // thread::spawn(move || {
            while let Ok(progress) = rx.recv() {
                ui.set_compressing_progress_value(progress);
                println!("{}", progress);
            }
            // });
        }
    });

    ui.run()
}

[ogoffart]

You shouldn't move the strong reference to the callback as that will cause leak (cycle in the refcount)

So move the (cloned) weak to the callback (also in on_choose_video_file) and move it again (cloned) in the thread,
and use the upgrade_in_event_loop function to go back to the UI loop:

ui.on_compress_video({
        let ui_handle = ui_handle.clone();  // clone the weak to move it to the callback
        move || {
            let (tx, rx) = std::sync::mpsc::channel::<f32>();
            // can unwrap in the callback, that's fine
            let input = ui_handle.unwrap().get_compress_video_input_file_path().clone();
            let input = std::path::Path::new(input.as_str());
            let video_type = "mp4";
            compress_video(input, video_type, tx);
            let ui_handle = ui_handle.clone(); // clone it again to move it to the thread
            thread::spawn(move || {
             while let Ok(progress) = rx.recv() {
                // use upgrade_in_event_loop to get a callback in the main thread again.
                ui_handle.upgrade_in_event_loop(move |ui| ui.set_compressing_progress_value(progress));
                println!("{}", progress);
              }
             });
        }
    });

I hope this helps.

[LeeeSe]

The slint staff is very quick to respond and the solutions are very effective, I hope slint grows from strength to strength!