webpin/src/WebAppWindow.vala

public class WebAppWindow : Gtk.ApplicationWindow {

    private bool is_full_screen = false;

    private string style_str =   """@define-color titlebar_color @titlebar_color;""";

    //widgets
    private WebApp web_app;
    private WebBar headerbar;

    public WebAppWindow (string webapp_name, string webapp_uri) {

        set_wmclass(webapp_uri, webapp_uri);
        web_app = new WebApp(webapp_name, webapp_uri);

        headerbar = new WebBar(web_app.external_view);
        headerbar.show_close_button = true;
        headerbar.title = webapp_name;
        headerbar.set_title_mode (WebBar.title_mode.TITLE);

        //style
        if (web_app.ui_color != "none") {
            try {
                print("set color");
                var style_cp = style_str.replace ("@titlebar_color", web_app.ui_color);
                var style_provider = new Gtk.CssProvider ();
                style_provider.load_from_data (style_cp, -1);
                headerbar.get_style_context ().add_provider (style_provider, -1);
                Gtk.Settings.get_default ().set ("gtk-application-prefer-dark-theme", should_use_dark_theme (web_app.ui_color));
            } catch (GLib.Error err) {
     	        warning("Loading style failed");
            }            
        }        

        web_app.theme_color_changed.connect( (color)=> {
            try {
                print("set color");
                var style_cp = style_str.replace ("@titlebar_color", color);
                var style_provider = new Gtk.CssProvider ();
                style_provider.load_from_data (style_cp, -1);
                headerbar.get_style_context ().add_provider (style_provider, -1);
                Gtk.Settings.get_default ().set ("gtk-application-prefer-dark-theme", should_use_dark_theme (color));
            } catch (GLib.Error err) {
     	        warning("Loading style failed");
            }
        });

        this.set_titlebar (headerbar);

        var info = DesktopFile.get_app_by_url(webapp_uri);
        var width = info.get_string("WebbyWindowWidth");
        var height = info.get_string("WebbyWindowHeight");

        if(width !=null && height != null)
          set_default_size (int.parse(width), int.parse(height));
        else
          set_default_size (1000, 600);
        this.delete_event.connect (() => {
            update_window_state(this.get_allocated_width (), this.get_allocated_height () );
            return false;
	      });

        this.destroy.connect(Gtk.main_quit);

        web_app.external_request.connect ( () => {
            print("Web app external request\n");
            web_app.set_transition_type (Gtk.StackTransitionType.SLIDE_LEFT);
            headerbar.set_title_mode (WebBar.title_mode.BROWSER);
            web_app.set_visible_child_name ("external");
        });

        headerbar.back_event.connect ( () => {
            print ("back");
            headerbar.set_title_mode (WebBar.title_mode.TITLE);
            web_app.set_transition_type (Gtk.StackTransitionType.SLIDE_RIGHT);
            web_app.set_visible_child_name ("app");
            //wait the animation to end before "cleaning" the web view
            GLib.Timeout.add(web_app.get_transition_duration(), () => {
                web_app.external_view.load_uri ("about:blank");
                return false;
            });
        });

        add(web_app);
        show_all();
    }

    public new void fullscreen () {
        is_full_screen = true;
        base.fullscreen();
    }

    public new void unfullscreen () {
        is_full_screen = false;
        base.unfullscreen();
    }

    public void toggle_fullscreen() {
        if(is_full_screen)
            unfullscreen();
        else
            fullscreen();
        is_full_screen = !is_full_screen;
    }

  public void update_window_state (int width, int height) {
      var file = web_app.get_desktop_file();
      file.edit_propertie ("WebbyWindowWidth", width.to_string());
      file.edit_propertie ("WebbyWindowHeight", height.to_string());
  }

    public override bool key_press_event (Gdk.EventKey event) {
        bool handled = true;
        switch (event.keyval) {
        case Gdk.Key.Escape:
            unfullscreen();
            break;
        case Gdk.Key.F11:
            toggle_fullscreen();
            break;
        default:
            handled = false;
            break;
        }

        if (handled)
            return true;

        return (base.key_press_event != null) ? base.key_press_event (event) : true;        
    }

    private bool should_use_dark_theme (string theme_color) {
        Gdk.RGBA color = {};
        color.parse (theme_color);

        double prom = (color.red + color.blue + color.green)/3;

        if (prom < 0.5)
            return true;
        return false;
    }
}