[Vala] How to write a responsive GTK+ app that reads a file in the background?

["Leonardo Ferreira Fontenelle" <leonardof gnome org>]

I'm trying to port a small Python GTK+ application to Vala. Overall, I
have succeeded, with some very interesting performance gains. But in
some cases the search may take a few seconds to finish, while the
application reads data from the disk. I tried using an async method to
keep the user interface responsive, but it didn't work: until the search
is completed, the user can't even move the cursor in the text entry
widget. What am I missing?

This is the relevant code; I hope the names are sufficiently
descriptive.



public void on_search_entry_activate (Gtk.Entry entry) {
        
        this.timer.start();
        
        this.search_progressbar.show();
        this.search_treeview.set_model(null);
        this.search_results.clear(); // this is a Gtk.ListStore
        
        string entry_text = entry.get_text();
        stdout.printf("Searching for: %s\n", entry_text);
        string[] words = this.word_regex.split(entry_text);
        this.search.begin(words, (obj, res) => {
                this.search.end(res);
                this.search_treeview.set_model(this.search_results);
                this.timer.stop();
                stdout.printf("%fs elapsed\n", this.timer.elapsed());
                this.search_progressbar.hide();
                this.search_progressbar.set_fraction(0.0);
        });
}

public async void search (string[] words) {
        
        Gee.TreeSet<int32> matches = get_matches (words);
        
        string code, title, inclusion_notes, exclusion_notes;
        //user-relevant data
        Gtk.TreeIter iter;
        double fraction = 0.0;
        double increment = 1.0 / matches.size;
        
        foreach (int32 match in matches) {
                get_node(match, out code, out title, out
                inclusion_notes, out exclusion_notes);
                this.search_results.append(out iter);
                this.search_results.set(iter, 0, match, 1, code, 2,
                title);
                fraction += increment;
                this.search_progressbar.set_fraction(fraction);
        }
}



Thanks in advance, 

Leonardo Fontenelle