24. Application

Gtk.Application 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.

24.1. 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.ModelButton 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().

24.3. 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.

24.4. Example

_images/application_example.png 
 1importsys
 2
 3importgi
 4
 5gi.require_version("Gtk", "3.0")
 6fromgi.repositoryimport GLib, Gio, Gtk
 7
 8# This would typically be its own file
 9MENU_XML = """
 10<?xml version="1.0" encoding="UTF-8"?>
 11<interface>
 12 <menu id="app-menu">
 13 <section>
 14 <attribute name="label" translatable="yes">Change label</attribute>
 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 <section>
 32 <item>
 33 <attribute name="action">win.maximize</attribute>
 34 <attribute name="label" translatable="yes">Maximize</attribute>
 35 </item>
 36 </section>
 37 <section>
 38 <item>
 39 <attribute name="action">app.about</attribute>
 40 <attribute name="label" translatable="yes">_About</attribute>
 41 </item>
 42 <item>
 43 <attribute name="action">app.quit</attribute>
 44 <attribute name="label" translatable="yes">_Quit</attribute>
 45 <attribute name="accel">&lt;Primary&gt;q</attribute>
 46 </item>
 47 </section>
 48 </menu>
 49</interface>
 50"""
 51
 52
 53classAppWindow(Gtk.ApplicationWindow):
 54 def__init__(self, *args, **kwargs):
 55 super().__init__(*args, **kwargs)
 56
 57 # This will be in the windows group and have the "win" prefix
 58 max_action = Gio.SimpleAction.new_stateful(
 59 "maximize", None, GLib.Variant.new_boolean(False)
 60 )
 61 max_action.connect("change-state", self.on_maximize_toggle)
 62 self.add_action(max_action)
 63
 64 # Keep it in sync with the actual state
 65 self.connect(
 66 "notify::is-maximized",
 67 lambda obj, pspec: max_action.set_state(
 68 GLib.Variant.new_boolean(obj.props.is_maximized)
 69 ),
 70 )
 71
 72 lbl_variant = GLib.Variant.new_string("String 1")
 73 lbl_action = Gio.SimpleAction.new_stateful(
 74 "change_label", lbl_variant.get_type(), lbl_variant
 75 )
 76 lbl_action.connect("change-state", self.on_change_label_state)
 77 self.add_action(lbl_action)
 78
 79 self.label = Gtk.Label(label=lbl_variant.get_string(), margin=30)
 80 self.add(self.label)
 81 self.label.show()
 82
 83 defon_change_label_state(self, action, value):
 84 action.set_state(value)
 85 self.label.set_text(value.get_string())
 86
 87 defon_maximize_toggle(self, action, value):
 88 action.set_state(value)
 89 if value.get_boolean():
 90 self.maximize()
 91 else:
 92 self.unmaximize()
 93
 94
 95classApplication(Gtk.Application):
 96 def__init__(self, *args, **kwargs):
 97 super().__init__(
 98 *args,
 99 application_id="org.example.myapp",
100 flags=Gio.ApplicationFlags.HANDLES_COMMAND_LINE,
101 **kwargs
102 )
103 self.window = None
104
105 self.add_main_option(
106 "test",
107 ord("t"),
108 GLib.OptionFlags.NONE,
109 GLib.OptionArg.NONE,
110 "Command line test",
111 None,
112 )
113
114 defdo_startup(self):
115 Gtk.Application.do_startup(self)
116
117 action = Gio.SimpleAction.new("about", None)
118 action.connect("activate", self.on_about)
119 self.add_action(action)
120
121 action = Gio.SimpleAction.new("quit", None)
122 action.connect("activate", self.on_quit)
123 self.add_action(action)
124
125 builder = Gtk.Builder.new_from_string(MENU_XML, -1)
126 self.set_app_menu(builder.get_object("app-menu"))
127
128 defdo_activate(self):
129 # We only allow a single window and raise any existing ones
130 if not self.window:
131 # Windows are associated with the application
132 # when the last one is closed the application shuts down
133 self.window = AppWindow(application=self, title="Main Window")
134
135 self.window.present()
136
137 defdo_command_line(self, command_line):
138 options = command_line.get_options_dict()
139 # convert GVariantDict -> GVariant -> dict
140 options = options.end().unpack()
141
142 if "test" in options:
143 # This is printed on the main instance
144 print("Test argument recieved: %s" % options["test"])
145
146 self.activate()
147 return 0
148
149 defon_about(self, action, param):
150 about_dialog = Gtk.AboutDialog(transient_for=self.window, modal=True)
151 about_dialog.present()
152
153 defon_quit(self, action, param):
154 self.quit()
155
156
157if __name__ == "__main__":
158 app = Application()
159 app.run(sys.argv)

24.5. See Also