Application

See also

For more detailed information about Gtk.Application checkout the Using GtkApplication tutorial.

Gtk.Application is the foundation for creating GTK apps. It encompasses many repetitive tasks that a modern application needs such as handling multiple instances, D-Bus activation, opening files, command line parsing, startup/shutdown, menu management, window management, and more.

In this example we will be also using Gtk.ApplicationWindow, it provides some extra features over regular Gtk.Window for main application windows.

Actions

Gio.Action is a way to expose any single task your application or widget does by a name. These actions can be disabled/enabled at runtime and they can either be activated or have a state changed (if they contain state).

The reason to use actions is to separate out the logic from the UI. For example this allows using a menubar on OSX and a gear menu on GNOME both simply referencing the name of an action. The main implementation of this you will be using is Gio.SimpleAction which will be demonstrated later.

Many classes such as Gio.MenuItem and Gtk.Actionable interface implementations like Gtk.Button support properties to set an action name.

These actions can be grouped together into a Gio.ActionGroup and when these groups are added to a widget with Gtk.Widget.insert_action_group() they will gain a prefix. Such as “win” when added to a Gtk.ApplicationWindow. You will use the full action name when referencing it such as “app.about” but when you create the action it will just be “about” until added to the application.

You can also very easily make keybindings for actions by setting the accel property in the Gio.Menu file or by using Gtk.Application.set_accels_for_action().

Command Line

When creating your application it takes a flag property of Gio.ApplicationFlags. Using this you can let it handle everything itself or have more custom behavior.

You can use HANDLES_COMMAND_LINE to allow custom behavior in Gio.Application.do_command_line(). In combination with Gio.Application.add_main_option() to add custom options.

Using HANDLES_OPEN will do the work of simply taking file arguments for you and let you handle it in Gio.Application.do_open().

If your application is already open these will all be sent to the existing instance unless you use NON_UNIQUE to allow multiple instances.

Example

../_images/application.png
  1import sys
  2import gi
  3
  4gi.require_version('Gtk', '4.0')
  5from gi.repository import GLib, Gio, Gtk
  6
  7# This would typically be its own file
  8MENU_XML = """
  9<?xml version="1.0" encoding="UTF-8"?>
 10<interface>
 11<menu id="menubar">
 12    <submenu>
 13        <attribute name="label" translatable="yes">Change label</attribute>
 14        <section>
 15            <item>
 16                <attribute name="action">win.change_label</attribute>
 17                <attribute name="target">String 1</attribute>
 18                <attribute name="label" translatable="yes">String 1</attribute>
 19            </item>
 20            <item>
 21                <attribute name="action">win.change_label</attribute>
 22                <attribute name="target">String 2</attribute>
 23                <attribute name="label" translatable="yes">String 2</attribute>
 24            </item>
 25            <item>
 26                <attribute name="action">win.change_label</attribute>
 27                <attribute name="target">String 3</attribute>
 28                <attribute name="label" translatable="yes">String 3</attribute>
 29            </item>
 30        </section>
 31    </submenu>
 32    <submenu>
 33        <attribute name="label" translatable="yes">Window</attribute>
 34        <section>
 35            <item>
 36                <attribute name="action">win.maximize</attribute>
 37                <attribute name="label" translatable="yes">Maximize</attribute>
 38            </item>
 39        </section>
 40        <section>
 41            <item>
 42                <attribute name="action">app.about</attribute>
 43                <attribute name="label" translatable="yes">_About</attribute>
 44            </item>
 45            <item>
 46                <attribute name="action">app.quit</attribute>
 47                <attribute name="label" translatable="yes">_Quit</attribute>
 48                <attribute name="accel">&lt;Primary&gt;q</attribute>
 49            </item>
 50        </section>
 51    </submenu>
 52</menu>
 53</interface>
 54"""
 55
 56
 57class AppWindow(Gtk.ApplicationWindow):
 58    def __init__(self, *args, **kwargs):
 59        super().__init__(*args, **kwargs)
 60
 61        self.set_default_size(200, 200)
 62
 63        # By default the title bar will be hide, let's show it
 64        self.props.show_menubar = True
 65
 66        # This will be in the windows group and have the 'win' prefix
 67        max_action = Gio.SimpleAction.new_stateful(
 68            'maximize', None, GLib.Variant.new_boolean(False)
 69        )
 70        max_action.connect('change-state', self.on_maximize_toggle)
 71        self.add_action(max_action)
 72
 73        # Keep it in sync with the actual state
 74        self.connect(
 75            'notify::maximized',
 76            lambda obj, _pspec: max_action.set_state(
 77                GLib.Variant.new_boolean(obj.props.maximized)
 78            ),
 79        )
 80
 81        lbl_variant = GLib.Variant.new_string('String 1')
 82        lbl_action = Gio.SimpleAction.new_stateful(
 83            'change_label', lbl_variant.get_type(), lbl_variant
 84        )
 85        lbl_action.connect('change-state', self.on_change_label_state)
 86        self.add_action(lbl_action)
 87
 88        self.label = Gtk.Label(label=lbl_variant.get_string())
 89        self.set_child(self.label)
 90
 91    def on_change_label_state(self, action, value):
 92        action.set_state(value)
 93        self.label.set_text(value.get_string())
 94
 95    def on_maximize_toggle(self, action, value):
 96        action.set_state(value)
 97        if value.get_boolean():
 98            self.maximize()
 99        else:
100            self.unmaximize()
101
102
103class Application(Gtk.Application):
104    def __init__(self, *args, **kwargs):
105        super().__init__(
106            *args,
107            application_id='org.example.App',
108            flags=Gio.ApplicationFlags.HANDLES_COMMAND_LINE,
109            **kwargs
110        )
111        self.window = None
112
113        self.add_main_option(
114            'test',
115            ord('t'),
116            GLib.OptionFlags.NONE,
117            GLib.OptionArg.NONE,
118            'Command line test',
119            None,
120        )
121
122    def do_startup(self):
123        Gtk.Application.do_startup(self)
124
125        action = Gio.SimpleAction.new('about', None)
126        action.connect('activate', self.on_about)
127        self.add_action(action)
128
129        action = Gio.SimpleAction.new('quit', None)
130        action.connect('activate', self.on_quit)
131        self.add_action(action)
132
133        builder = Gtk.Builder.new_from_string(MENU_XML, -1)
134        self.set_menubar(builder.get_object('menubar'))
135
136    def do_activate(self):
137        # We only allow a single window and raise any existing ones
138        if not self.window:
139            # Windows are associated with the application
140            # when the last one is closed the application shuts down
141            self.window = AppWindow(application=self, title='Main Window')
142
143        self.window.present()
144
145    def do_command_line(self, command_line):
146        options = command_line.get_options_dict()
147        # convert GVariantDict -> GVariant -> dict
148        options = options.end().unpack()
149
150        if 'test' in options:
151            # This is printed on the main instance
152            print('Test argument recieved: %s' % options['test'])
153
154        self.activate()
155        return 0
156
157    def on_about(self, _action, _param):
158        about_dialog = Gtk.AboutDialog(transient_for=self.window, modal=True)
159        about_dialog.present()
160
161    def on_quit(self, _action, _param):
162        self.quit()
163
164
165if __name__ == '__main__':
166    app = Application()
167    app.run(sys.argv)