Taiko's GTK4 Python tutorial

Wanna make apps for Linux but not sure how to start with GTK? Frustrated with the style of GTK4 documentation. This guide will hopefully get you started!

Prerequisite: You have learnt the basics of Python

Topics:

• A basic window
• A button
• A layout box
• A check button
• A switch
• A Label
• A slider
• Header bar
• Button with menu

A most basic program

import gi
gi.require_version('Gtk', '4.0')
from gi.repository import Gtk

def on_activate(app):
    win = Gtk.ApplicationWindow(application=app)
    win.present()

app = Gtk.Application(application_id='com.example.GtkApplication')
app.connect('activate', on_activate)

app.run(None)

This should display a small blank window.

Oh btw, you'll want to think of an application id for your app, especially if you're going to distribute it. It should be the reverse of a domain or page you control. If you dont have your own domain you can do like "com.github.me.myproject".

Right um... lets make that code into classes! Cause doing it functional style is a little awkward in Python.

Also, Libawaita is the new hotness, so lets switch to that!

Aaand we'll pass the app arguments in.

Here's what we got now:

A better structured basic GTK4 + Adwaita

import sys
import gi
gi.require_version('Gtk', '4.0')
gi.require_version('Adw', '1')
from gi.repository import Gtk, Adw


class MainWindow(Gtk.ApplicationWindow):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
	# Things will go here

class MyApp(Adw.Application):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.connect('activate', self.on_activate)

    def on_activate(self, app):
        self.win = MainWindow(application=app)
        self.win.present()

app = MyApp(application_id="com.example.GtkApplication")
app.run(sys.argv)

Soo we have an instance of an app class and a window which we extend! We run our app and it makes a window!

Tip: Don't worry too much if your Python knowledge isn't strong and the __init__(self, *args, **kwargs) stuff is giving you a headache.

So! Whats next?

Well, we want to add something to our window. That would likely be a layout of some sort!

Most basic layout is a Box.

Lets add a box to the window! (Where the comment "things will go here" is above)

self.box = Gtk.Box()
self.set_child(self.box)

We make a new box, and attach it to the window. Simple. If you run the app now you'll see no difference, because there's nothing in the layout yet either.

Add a button!

One of the most basic widgets is a Button. Let's make one and add it to the layout.

self.button = Gtk.Button(label="Hello")
self.box1.append(self.button)

Now our app has a button! (The window will be small now)

But it does nothing when we click it. Let's connect it to a function! Make a new method that prints hello world, and we connect it!

Here's our MainWindow so far:

class MainWindow(Gtk.ApplicationWindow):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.box1 = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)
        self.set_child(self.box1)

        self.button = Gtk.Button(label="Hello")
        self.box1.append(self.button)
        self.button.connect('clicked', self.hello)

    def hello(self, button):
        print("Hello world")

Cool eh?

By the way the Box layout lays out widgets in like a vertical or horizontal order. We should set the orientation of the box. See the change:

self.box1 = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)

Quick intermission, lets set some fun stuff

self.set_default_size(600, 250)
self.set_title("MyApp")

More boxes

You'll notice our button is stretched with the window. Let's add two boxes inside that first box we made.

self.box1 = Gtk.Box(orientation=Gtk.Orientation.HORIZONTAL)
self.box2 = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)
self.box3 = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)

self.button = Gtk.Button(label="Hello")
self.button.connect('clicked', self.hello)

self.set_child(self.box1)  # Horizontal box to window
self.box1.append(self.box2)  # Put vert box in that box
self.box1.append(self.box3)  # And another one, empty for now

self.box2.append(self.button) # But button in the first of the two vertial boxes

Now that's more neat!

Add a check button!

So, we know about a button, next lets add a Checkbutton.

    ...
    self.check = Gtk.CheckButton(label="And goodbye?")
    self.box2.append(self.check)


def hello(self, button):
    print("Hello world")
    if self.check.get_active():
        print("Goodbye world!")
        self.close()

When we click the button, we can check the state of the checkbox!

Add a switch

For our switch, we'll want to put our switch in a Box, otherwise it'll look all stretched.

        ...
        self.switch_box = Gtk.Box(orientation=Gtk.Orientation.HORIZONTAL)

        self.switch = Gtk.Switch()
        self.switch.set_active(True)  # Let's default it to on
        self.switch.connect("state-set", self.switch_switched) # Lets trigger a function

        self.switch_box.append(self.switch)
        self.box2.append(self.switch_box)

    def switch_switched(self, switch, state):
        print(f"The switch has been switched {'on' if state else 'off'}")

Try it out!

Our switch is looking rather nondescript, so lets add a label to it!

Add a Label

A label is like a basic line of text

self.label = Gtk.Label(label="A switch")
self.switch_box.append(self.switch)
self.switch_box.set_spacing(5) # Add some spacing

It should look like this now:

The file part1.py is an example of the code so far.

Adding a slider (Aka scale)

Here's an example of adding a Scale with a range from 0 - 10

        self.slider = Gtk.Scale()
        self.slider.set_digits(0)  # Number of decimal places to use
        self.slider.set_range(0, 10)
        self.slider.set_draw_value(True)  # Show a label with current value
        self.slider.set_value(5)  # Sets the current value/position
        self.slider.connect('value-changed', self.slider_changed)
        self.box2.append(self.slider)

    def slider_changed(self, slider):
        print(int(slider.get_value()))

Adding a button into the header bar

First we need to make a header bar

        self.header = Gtk.HeaderBar()
        self.set_titlebar(self.header)

Simple.

Now add a button

        self.open_button = Gtk.Button(label="Open")
        self.header.pack_start(self.open_button)

We already know how to connect a function to the button, so i've omitted that.

Done! But... it would look nicer with an icon rather than text.

        self.open_button.set_icon_name("document-open-symbolic")

This will be an icon name from the icon theme.

For some defaults you can take a look at /usr/share/icons/Adwaita/scalable/actions.

If you were adding a new action icon it would go in /usr/share/icons/hicolor/scalable/actions

Help! Todo! Is this the best way? How do icons work in a development environment?

Adding a button with menu

For this there are multiple new concepts we need to introduce:

• The MenuButton widget.
• The Popover, but here we will use a PopoverMenu which is built using an abstract menu model.
• A Menu. This is an abstract model of a menu.
• Actions. An abstract action that can be connected to our abstract menu.

First, lets add a MenuButton to our header bar

        # Create a new "Action"
        action = Gio.SimpleAction.new("something", None)
        action.connect("activate", self.print_something)
        self.add_action(action)  # Here the action is being added to the window, but you could add it to the
                                 # application or an "ActionGroup"

        # Create a new menu, containing that action
        menu = Gio.Menu.new()
        menu.append("Do Something", "win.something")  # Or you would do app.grape if you had attached the
                                                      # action to the application

        # Create a popover
        self.popover = Gtk.PopoverMenu()  # Create a new popover menu
        self.popover.set_menu_model(menu)

        # Create a menu button
        self.hamburger = Gtk.MenuButton()
        self.hamburger.set_popover(self.popover)
        self.hamburger.set_icon_name("open-menu-symbolic")  # Give it a nice icon

        # Add menu button to the header bar
        self.header.pack_start(self.hamburger)

    def print_something(self, action, param):
        print("Something!")

WIP

Todo...

Text box: Entry

Number changer: SpinButton