CheckButton (JavaScript)

This application has a CheckButton. Whether the box is checked dictates whether the window's title bar shows anything.

A CheckButton sends the "toggled" signal when it's checked or unchecked. While it's checked, the "active" property is true. While it's not, "active" tests as false.

Libraries to import

These are the libraries we need to import for this application to run. Remember that the line which tells GNOME that we're using Gjs always needs to go at the start.

Creating the application window

All the code for this sample goes in the CheckButtonExample class. The above code creates a Gtk.Application for our widgets and window to go in.

The _buildUI function is where we put all the code to create the application's user interface. The first step is creating a new Gtk.ApplicationWindow to put all our widgets into.

Creating the checkbutton

This code creates the checkbutton itself. The label next to the checkbutton is created by giving the checkbutton the "label" property and assigning a string value to it. Since this checkbutton toggles whether the window title is on or off, and the window title will be on to start with, we want the box to be checked by default. Whenever the user checks or unchecks the box, we call the _toggledCB function.

This code finishes up creating the UI, by telling the window to show itself and all child widgets (which is just the checkbutton in this case).

Function which handles the checkbutton's toggling

If the checkbutton is toggled from on to off, we want the window title to disappear. If it's toggled from off to on, we want it to reappear. We can tell which way it was toggled by testing to see whether it's active (checked) or not afterwards. A simple if / else statement which calls the checkbutton's get_active() method will work for this.

Finally, we create a new instance of the finished CheckButtonExample class, and set the application running.

Amostra de código completo

#!/usr/bin/gjs

imports.gi.versions.Gtk = '3.0';

const Gio = imports.gi.Gio;
const Gtk = imports.gi.Gtk;

class CheckButtonExample {

    // Create the application itself
    constructor() {
        this.application = new Gtk.Application({
            application_id: 'org.example.jscheckbutton',
            flags: Gio.ApplicationFlags.FLAGS_NONE
        });

        // Connect 'activate' and 'startup' signals to the callback functions
        this.application.connect('activate', this._onActivate.bind(this));
        this.application.connect('startup', this._onStartup.bind(this));
    }

    // Callback function for 'activate' signal presents window when active
    _onActivate() {
        this._window.present();
    }

    // Callback function for 'startup' signal builds the UI
    _onStartup() {
        this._buildUI();
    }

    // Build the application's UI
    _buildUI() {

        // Create the application window
        this._window = new Gtk.ApplicationWindow({
            application: this.application,
            window_position: Gtk.WindowPosition.CENTER,
            default_height: 100,
            default_width: 300,
            border_width: 10,
            title: "CheckButton Example"});

        // Create the check button
        this._button = new Gtk.CheckButton ({label: "Show Title"});
        this._window.add (this._button);

        // Have the check button be checked by default
        this._button.set_active (true);

        // Connect the button to a function that does something when it's toggled
        this._button.connect ("toggled", this._toggledCB.bind(this));

        // Show the window and all child widgets
        this._window.show_all();
    }

    _toggledCB() {

        // Make the window title appear or disappear when the checkbox is toggled
        if (this._button.get_active() == true)
            this._window.set_title ("CheckButton Example");
        else
            this._window.set_title ("");

    }

};

// Run the application
let app = new CheckButtonExample ();
app.application.run (ARGV);

In-depth documentation

Gtk.Application

Gtk.ApplicationWindow

Gtk.CheckButton