How does one resize a GtkImage with a window resize?

[plijjwi]

Hello again,

I’m working on a project that allows selecting a video and using it as a bootscreen. To so, when the user selects a video, a thumbnail should be shown.

The is that once GtkImage gets a large image, the whole window resizes to fit the new size and it’s not possible to make the window smaller anymore; only larger.
In the python implementation (using Qt), the original thumbnail is stored and at every resize it’s used to generate a new, scaled thumbnail to fit the widget.

How would one achieve the same thing in Gtk-rs?

Excuse the beginner rust, but it looks like this atm (no resizing)

    let chooser__video: FileChooserButton = builder.get_object("chooser__video").unwrap();
    let label__thumbnail: Image = builder.get_object("label__thumbnail").unwrap();
    chooser__video.connect_file_set(move |chooser| {
        let option = chooser.get_file();
        if option.is_none() {
            return;
        }
        let file = option.unwrap();
        if file.get_path().is_none() {
            return;
        }
        let thumbnail = ffmpeg::get_video_thumbnail(file.get_path().unwrap().to_str().unwrap());
        if thumbnail.is_some() {
            label__thumbnail.set_from_pixbuf(Option::from(&thumbnail))
        } else {
            todo!("Handle error handling")
        }
    });

I tried putting that code into a struct to store the thumbnail, but couldn’t get it to work.

pub struct Application {
    thumbnail: Option<Pixbuf>,
    pub builder: Builder,
}

impl Application {
  pub fn connect(&mut self) {
     // ...
    chooser__video.connect_file_set(move |chooser| {
      // ...
      let thumbnail: Pixbuf = ffmpeg::get_video_thumbnail(file.get_path().unwrap().to_str().unwrap()).unwrap();
      self.thumbnail = Option::from(thumbnail);  // --> closures cannot mutate their captured variables
      let size = label__thumbnail.get_size_request();
      let new_thumbnail = thumbnail.scale_simple(size.0, size.1, InterpType::Bilinear);
      label__thumbnail.set_from_pixbuf(Option::from(&new_thumbnail));
    });
  }
}

It does look like a solution that I found in C, but I can’t think rust yet.

How could I get this to work in rust?