Sets our main struct and passes it to the parent class
Creates a new GApplication instance. If non-NULL, the application id must be valid. See g_application_id_is_valid(). If no application ID is given then some features of GApplication (most notably application uniqueness) will be disabled.
Activates the application. In essence, this results in the "activate" signal being emitted in the primary instance. The application must be registered before calling this function. Since 2.28
The ::activate signal is emitted on the primary instance when an activation occurs. See g_application_activate().
The ::command-line signal is emitted on the primary instance when a commandline is not handled locally. See g_application_run() and the GApplicationCommandLine documentation for more information.
The ::open signal is emitted on the primary instance when there are files to open. See g_application_open() for more information.
The ::shutdown signal is emitted only on the registered primary instance immediately after the main loop terminates.
The ::startup signal is emitted on the primary instance immediately after registration. See g_application_register().
Gets the unique identifier for application. Since 2.28
Gets the GDBusConnection being used by the application, or NULL. If GApplication is using its D-Bus backend then this function will return the GDBusConnection being used for uniqueness and communication with the desktop environment and other instances of the application. If GApplication is not using D-Bus then this function will return NULL. This includes the situation where the D-Bus backend would normally be in use but we were unable to connect to the bus. This function must not be called before the application has been registered. See g_application_get_is_registered(). Since 2.34
Gets the D-Bus object path being used by the application, or NULL. If GApplication is using its D-Bus backend then this function will return the D-Bus object path that GApplication is using. If the application is the primary instance then there is an object published at this path. If the application is not the primary instance then the result of this function is undefined. If GApplication is not using D-Bus then this function will return NULL. This includes the situation where the D-Bus backend would normally be in use but we were unable to connect to the bus. This function must not be called before the application has been registered. See g_application_get_is_registered(). Since 2.34
Gets the flags for application. See GApplicationFlags. Since 2.28
Gets the current inactivity timeout for the application. This is the amount of time (in milliseconds) after the last call to g_application_release() before the application stops running. Since 2.28
Checks if application is registered. An application is registered if g_application_register() has been successfully called. Since 2.28
Checks if application is remote. If application is remote then it means that another instance of application already exists (the 'primary' instance). Calls to perform actions on application will result in the actions being performed by the primary instance. The value of this property cannot be accessed before g_application_register() has been called. See g_application_get_is_registered(). Since 2.28
the main Gtk struct as a void*
Increases the use count of application. Use this function to indicate that the application has a reason to continue to run. For example, g_application_hold() is called by GTK+ when a toplevel window is on the screen. To cancel the hold, call g_application_release().
Increases the busy count of application. Use this function to indicate that the application is busy, for instance while a long running operation is pending. The busy state will be exposed to other processes, so a session shell will use that information to indicate the state to the user (e.g. with a spinner). To cancel the busy indication, use g_application_unmark_busy(). Since 2.38
Opens the given files. In essence, this results in the "open" signal being emitted in the primary instance. n_files must be greater than zero. hint is simply passed through to the ::open signal. It is intended to be used by applications that have multiple modes for opening files (eg: "view" vs "edit", etc). Unless you have a need for this functionality, you should use "". The application must be registered before calling this function and it must have the G_APPLICATION_HANDLES_OPEN flag set. Since 2.28
Immediately quits the application. Upon return to the mainloop, g_application_run() will return, calling only the 'shutdown' function before doing so. The hold count is ignored. The result of calling g_application_run() again after it returns is unspecified. Since 2.32
Attempts registration of the application. This is the point at which the application discovers if it is the primary instance or merely acting as a remote for an already-existing primary instance. This is implemented by attempting to acquire the application identifier as a unique bus name on the session bus using GDBus. If there is no application ID or if G_APPLICATION_NON_UNIQUE was given, then this process will always become the primary instance. Due to the internal architecture of GDBus, method calls can be dispatched at any time (even if a main loop is not running). For this reason, you must ensure that any object paths that you wish to register are registered before calling this function. If the application has already been registered then TRUE is returned with no work performed. The "startup" signal is emitted if registration succeeds and application is the primary instance (including the non-unique case). In the event of an error (such as cancellable being cancelled, or a failure to connect to the session bus), FALSE is returned and error is set appropriately. Note: the return value of this function is not an indicator that this instance is or is not the primary instance of the application. See g_application_get_is_remote() for that. Since 2.28
Decrease the use count of application. When the use count reaches zero, the application will stop running. Never call this function except to cancel the effect of a previous call to g_application_hold().
Runs the application. This function is intended to be run from main() and its return value is intended to be returned by main(). Although you are expected to pass the argc, argv parameters from main() to this function, it is possible to pass NULL if argv is not available or commandline handling is not required. First, the local_command_line() virtual function is invoked. This function always runs on the local instance. It gets passed a pointer to a NULL-terminated copy of argv and is expected to remove the arguments that it handled (shifting up remaining arguments). See Example 23, “Split commandline handling” for an example of parsing argv manually. Alternatively, you may use the GOptionContext API, after setting argc = g_strv_length (argv);. The last argument to local_command_line() is a pointer to the status variable which can used to set the exit status that is returned from g_application_run(). If local_command_line() returns TRUE, the command line is expected to be completely handled, including possibly registering as the primary instance, calling g_application_activate() or g_application_open(), etc. If local_command_line() returns FALSE then the application is registered and the "command-line" signal is emitted in the primary instance (which may or may not be this instance). The signal handler gets passed a GApplicationCommandLine object that (among other things) contains the remaining commandline arguments that have not been handled by local_command_line(). If the application has the G_APPLICATION_HANDLES_COMMAND_LINE flag set then the default implementation of local_command_line() always returns FALSE immediately, resulting in the commandline always being handled in the primary instance. Otherwise, the default implementation of local_command_line() tries to do a couple of things that are probably reasonable for most applications. First, g_application_register() is called to attempt to register the application. If that works, then the command line arguments are inspected. If no commandline arguments are given, then g_application_activate() is called. If commandline arguments are given and the G_APPLICATION_HANDLES_OPEN flag is set then they are assumed to be filenames and g_application_open() is called. If you need to handle commandline arguments that are not filenames, and you don't mind commandline handling to happen in the primary instance, you should set G_APPLICATION_HANDLES_COMMAND_LINE and process the commandline arguments in your "command-line" signal handler, either manually or using the GOptionContext API. If you are interested in doing more complicated local handling of the commandline then you should implement your own GApplication subclass and override local_command_line(). In this case, you most likely want to return TRUE from your local_command_line() implementation to suppress the default handling. See Example 23, “Split commandline handling” for an example. If, after the above is done, the use count of the application is zero then the exit status is returned immediately. If the use count is non-zero then the default main context is iterated until the use count falls to zero, at which point 0 is returned. If the G_APPLICATION_IS_SERVICE flag is set, then the service will run for as much as 10 seconds with a use count of zero while waiting for the message that caused the activation to arrive. After that, if the use count falls to zero the application will exit immediately, except in the case that g_application_set_inactivity_timeout() is in use. This function sets the prgname (g_set_prgname()), if not already set, to the basename of argv[0]. Since 2.38, if G_APPLICATION_IS_SERVICE is specified, the prgname is set to the application ID. The main impact of this is is that the wmclass of windows created by Gtk+ will be set accordingly, which helps the window manager determine which application is showing the window. Since 2.28
Warning g_application_set_action_group has been deprecated since version 2.32 and should not be used in newly-written code. Use the GActionMap interface instead. Never ever mix use of this API with use of GActionMap on the same application or things will go very badly wrong. This function is known to introduce buggy behaviour (ie: signals not emitted on changes to the action group), so you should really use GActionMap instead. This used to be how actions were associated with a GApplication. Now there is GActionMap for that. Since 2.28
Sets the unique identifier for application. The application id can only be modified if application has not yet been registered. If non-NULL, the application id must be valid. See g_application_id_is_valid(). Since 2.28
Sets or unsets the default application for the process, as returned by g_application_get_default(). This function does not take its own reference on application. If application is destroyed then the default application will revert back to NULL. Since 2.32
Sets the flags for application. The flags can only be modified if application has not yet been registered. See GApplicationFlags. Since 2.28
Sets the current inactivity timeout for the application. This is the amount of time (in milliseconds) after the last call to g_application_release() before the application stops running. This call has no side effects of its own. The value set here is only used for next time g_application_release() drops the use count to zero. Any timeouts currently in progress are not impacted. Since 2.28
Decreases the busy count of application. When the busy count reaches zero, the new state will be propagated to other processes. This function must only be called to cancel the effect of a previous call to g_application_mark_busy(). Since 2.38
Returns the default GApplication instance for this process. Normally there is only one GApplication per process and it becomes the default when it is created. You can exercise more control over this by using g_application_set_default(). If there is no default application then NULL is returned. Since 2.32
Checks if application_id is a valid application identifier. A valid ID is required for calls to g_application_new() and g_application_set_application_id(). For convenience, the restrictions on application identifiers are
the main Gtk struct
the main Gtk struct
the main Gtk struct as a void*
Gets a D Object from the objects table of associations.
The notify signal is emitted on an object when one of its properties has been changed. Note that getting this signal doesn't guarantee that the value of the property has actually changed, it may also be emitted when the setter for the property is called to reinstate the previous value.
Installs a new property. This is usually done in the class initializer. Note that it is possible to redefine a property in a derived class, by installing a property with the same name. This can be useful at times, e.g. to change the range of allowed values or the default value.
Installs new properties from an array of GParamSpecs. This is usually done in the class initializer. The property id of each property is the index of each GParamSpec in the pspecs array. The property id of 0 is treated specially by GObject and it should not be used to store a GParamSpec. This function should be used if you plan to use a static array of GParamSpecs and g_object_notify_by_pspec(). For instance, this Since 2.26
Looks up the GParamSpec for a property of a class.
Get an array of GParamSpec* for all properties of a class.
Registers property_id as referring to a property with the name name in a parent class or in an interface implemented by oclass. This allows this class to override a property implementation in a parent class or to provide the implementation of a property from an interface. Note Internally, overriding is implemented by creating a property of type GParamSpecOverride; generally operations that query the properties of the object class, such as g_object_class_find_property() or g_object_class_list_properties() will return the overridden property. However, in one case, the construct_properties argument of the constructor virtual function, the GParamSpecOverride is passed instead, so that the param_id field of the GParamSpec will be correct. For virtually all uses, this makes no difference. If you need to get the overridden property, you can call g_param_spec_get_redirect_target(). Since 2.4
Add a property to an interface; this is only useful for interfaces that are added to GObject-derived types. Adding a property to an interface forces all objects classes with that interface to have a compatible property. The compatible property could be a newly created GParamSpec, but normally g_object_class_override_property() will be used so that the object class only needs to provide an implementation and inherits the property description, default value, bounds, and so forth from the interface property. This function is meant to be called from the interface's default vtable initialization function (the class_init member of GTypeInfo.) It must not be called after after class_init has been called for any object types implementing this interface. Since 2.4
Find the GParamSpec with the given name for an interface. Generally, the interface vtable passed in as g_iface will be the default vtable from g_type_default_interface_ref(), or, if you know the interface has already been loaded, g_type_default_interface_peek(). Since 2.4
Lists the properties of an interface.Generally, the interface vtable passed in as g_iface will be the default vtable from g_type_default_interface_ref(), or, if you know the interface has already been loaded, g_type_default_interface_peek(). Since 2.4
Increases the reference count of object.
Decreases the reference count of object. When its reference count drops to 0, the object is finalized (i.e. its memory is freed).
Increase the reference count of object, and possibly remove the floating reference, if object has a floating reference. In other words, if the object is floating, then this call "assumes ownership" of the floating reference, converting it to a normal reference by clearing the floating flag while leaving the reference count unchanged. If the object is not floating, then this call adds a new normal reference increasing the reference count by one. Since 2.10
Clears a reference to a GObject. object_ptr must not be NULL. If the reference is NULL then this function does nothing. Otherwise, the reference count of the object is decreased and the pointer is set to NULL. This function is threadsafe and modifies the pointer atomically, using memory barriers where needed. A macro is also included that allows this function to be used without pointer casts. Since 2.28
Checks whether object has a floating reference. Since 2.10
This function is intended for GObject implementations to re-enforce a floating object reference. Doing this is seldom required: all GInitiallyUnowneds are created with a floating reference which usually just needs to be sunken by calling g_object_ref_sink(). Since 2.10
Adds a weak reference callback to an object. Weak references are used for notification when an object is finalized. They are called "weak references" because they allow you to safely hold a pointer to an object without calling g_object_ref() (g_object_ref() adds a strong reference, that is, forces the object to stay alive). Note that the weak references created by this method are not thread-safe: they cannot safely be used in one thread if the object's last g_object_unref() might happen in another thread. Use GWeakRef if thread-safety is required.
Removes a weak reference callback to an object.
Adds a weak reference from weak_pointer to object to indicate that the pointer located at weak_pointer_location is only valid during the lifetime of object. When the object is finalized, weak_pointer will be set to NULL. Note that as with g_object_weak_ref(), the weak references created by this method are not thread-safe: they cannot safely be used in one thread if the object's last g_object_unref() might happen in another thread. Use GWeakRef if thread-safety is required.
Removes a weak reference from object that was previously added using g_object_add_weak_pointer(). The weak_pointer_location has to match the one used with g_object_add_weak_pointer().
Increases the reference count of the object by one and sets a callback to be called when all other references to the object are dropped, or when this is already the last reference to the object and another reference is established. This functionality is intended for binding object to a proxy object managed by another memory manager. This is done with two paired references: the strong reference added by g_object_add_toggle_ref() and a reverse reference to the proxy object which is either a strong reference or weak reference. The setup is that when there are no other references to object, only a weak reference is held in the reverse direction from object to the proxy object, but when there are other references held to object, a strong reference is held. The notify callback is called when the reference from object to the proxy object should be toggled from strong to weak (is_last_ref true) or weak to strong (is_last_ref false). Since a (normal) reference must be held to the object before calling g_object_add_toggle_ref(), the initial state of the reverse link is always strong. Multiple toggle references may be added to the same gobject, however if there are multiple toggle references to an object, none of them will ever be notified until all but one are removed. For this reason, you should only ever use a toggle reference if there is important state in the proxy object. Since 2.8
Removes a reference added with g_object_add_toggle_ref(). The reference count of the object is decreased by one. Since 2.8
Emits a "notify" signal for the property property_name on object. When possible, eg. when signaling a property change from within the class that registered the property, you should use g_object_notify_by_pspec() instead.
Emits a "notify" signal for the property specified by pspec on object. This function omits the property name lookup, hence it is faster than g_object_notify(). One way to avoid using g_object_notify() from within the class that registered the properties, and using g_object_notify_by_pspec() instead, is to store the GParamSpec used with Since 2.26
Increases the freeze count on object. If the freeze count is non-zero, the emission of "notify" signals on object is stopped. The signals are queued until the freeze count is decreased to zero. Duplicate notifications are squashed so that at most one "notify" signal is emitted for each property modified while the object is frozen. This is necessary for accessors that modify multiple properties to prevent premature notification while the object is still being modified.
Reverts the effect of a previous call to g_object_freeze_notify(). The freeze count is decreased on object and when it reaches zero, queued "notify" signals are emitted. Duplicate notifications for each property are squashed so that at most one "notify" signal is emitted for each property. It is an error to call this function when the freeze count is zero.
Gets a named field from the objects table of associations (see g_object_set_data()).
Each object carries around a table of associations from strings to pointers. This function lets you set an association. If the object already had an association with that name, the old association will be destroyed.
Like g_object_set_data() except it adds notification for when the association is destroyed, either by setting it to a different value or when the object is destroyed. Note that the destroy callback is not called if data is NULL.
Remove a specified datum from the object's data associations, without invoking the association's destroy handler.
This is a variant of g_object_get_data() which returns a 'duplicate' of the value. dup_func defines the meaning of 'duplicate' in this context, it could e.g. take a reference on a ref-counted object. If the key is not set on the object then dup_func will be called with a NULL argument. Note that dup_func is called while user data of object is locked. This function can be useful to avoid races when multiple threads are using object data on the same key on the same object. Since 2.34
Compares the user data for the key key on object with oldval, and if they are the same, replaces oldval with newval. This is like a typical atomic compare-and-exchange operation, for user data on an object. If the previous value was replaced then ownership of the old value (oldval) is passed to the caller, including the registered destroy notify for it (passed out in old_destroy). Its up to the caller to free this as he wishes, which may or may not include using old_destroy as sometimes replacement should not destroy the object in the normal way. Return: TRUE if the existing value for key was replaced by newval, FALSE otherwise. Since 2.34
This function gets back user data pointers stored via g_object_set_qdata().
This sets an opaque, named pointer on an object. The name is specified through a GQuark (retrived e.g. via g_quark_from_static_string()), and the pointer can be gotten back from the object with g_object_get_qdata() until the object is finalized. Setting a previously set user data pointer, overrides (frees) the old pointer set, using NULL as pointer essentially removes the data stored.
This function works like g_object_set_qdata(), but in addition, a void (*destroy) (gpointer) function may be specified which is called with data as argument when the object is finalized, or the data is being overwritten by a call to g_object_set_qdata() with the same quark.
This function gets back user data pointers stored via g_object_set_qdata() and removes the data from object without invoking its destroy() function (if any was set). Usually, calling this function is only required to update
This is a variant of g_object_get_qdata() which returns a 'duplicate' of the value. dup_func defines the meaning of 'duplicate' in this context, it could e.g. take a reference on a ref-counted object. If the quark is not set on the object then dup_func will be called with a NULL argument. Note that dup_func is called while user data of object is locked. This function can be useful to avoid races when multiple threads are using object data on the same key on the same object. Since 2.34
Compares the user data for the key quark on object with oldval, and if they are the same, replaces oldval with newval. This is like a typical atomic compare-and-exchange operation, for user data on an object. If the previous value was replaced then ownership of the old value (oldval) is passed to the caller, including the registered destroy notify for it (passed out in old_destroy). Its up to the caller to free this as he wishes, which may or may not include using old_destroy as sometimes replacement should not destroy the object in the normal way. Return: TRUE if the existing value for quark was replaced by newval, FALSE otherwise. Since 2.34
Sets a property on an object.
Gets a property of an object. value must have been initialized to the expected type of the property (or a type to which the expected type can be transformed) using g_value_init(). In general, a copy is made of the property contents and the caller is responsible for freeing the memory by calling g_value_unset(). Note that g_object_get_property() is really intended for language bindings, g_object_get() is much more convenient for C programming.
Sets properties on an object.
Gets properties of an object. In general, a copy is made of the property contents and the caller is responsible for freeing the memory in the appropriate manner for the type, for instance by calling g_free() or g_object_unref(). See g_object_get().
This function essentially limits the life time of the closure to the life time of the object. That is, when the object is finalized, the closure is invalidated by calling g_closure_invalidate() on it, in order to prevent invocations of the closure with a finalized (nonexisting) object. Also, g_object_ref() and g_object_unref() are added as marshal guards to the closure, to ensure that an extra reference count is held on object during invocation of the closure. Usually, this function will be called on closures that use this object as closure data.
Releases all references to other objects. This can be used to break reference cycles. This functions should only be called from object system implementations.
the main Gtk struct as a void*
Signals that a new action was just added to the group. This signal is emitted after the action has been added and is now visible. Since 2.28
Signals that the enabled status of the named action has changed. Since 2.28
Signals that an action is just about to be removed from the group. This signal is emitted before the action is removed, so the action is still visible and can be queried from the signal handler. Since 2.28
Signals that the state of the named action has changed. Since 2.28 See Also GAction
Lists the actions contained within action_group. The caller is responsible for freeing the list with g_strfreev() when it is no longer required. Since 2.28
Queries all aspects of the named action within an action_group. This function acquires the information available from g_action_group_has_action(), g_action_group_get_action_enabled(), g_action_group_get_action_parameter_type(), g_action_group_get_action_state_type(), g_action_group_get_action_state_hint() and g_action_group_get_action_state() with a single function call. This provides two main benefits. The first is the improvement in efficiency that comes with not having to perform repeated lookups of the action in order to discover different things about it. The second is that implementing GActionGroup can now be done by only overriding this one virtual function. The interface provides a default implementation of this function that calls the individual functions, as required, to fetch the information. The interface also provides default implementations of those functions that call this function. All implementations, therefore, must override either this function or all of the others. If the action exists, TRUE is returned and any of the requested fields (as indicated by having a non-NULL reference passed in) are filled. If the action doesn't exist, FALSE is returned and the fields may or may not have been modified. Since 2.32
Checks if the named action exists within action_group. Since 2.28
Checks if the named action within action_group is currently enabled. An action must be enabled in order to be activated or in order to have its state changed from outside callers. Since 2.28
Queries the type of the parameter that must be given when activating the named action within action_group. When activating the action using g_action_group_activate_action(), the GVariant given to that function must be of the type returned by this function. In the case that this function returns NULL, you must not give any GVariant, but NULL instead. The parameter type of a particular action will never change but it is possible for an action to be removed and for a new action to be added with the same name but a different parameter type. Since 2.28
Queries the type of the state of the named action within action_group. If the action is stateful then this function returns the GVariantType of the state. All calls to g_action_group_change_action_state() must give a GVariant of this type and g_action_group_get_action_state() will return a GVariant of the same type. If the action is not stateful then this function will return NULL. In that case, g_action_group_get_action_state() will return NULL and you must not call g_action_group_change_action_state(). The state type of a particular action will never change but it is possible for an action to be removed and for a new action to be added with the same name but a different state type. Since 2.28
Requests a hint about the valid range of values for the state of the named action within action_group. If NULL is returned it either means that the action is not stateful or that there is no hint about the valid range of values for the state of the action. If a GVariant array is returned then each item in the array is a possible value for the state. If a GVariant pair (ie: two-tuple) is returned then the tuple specifies the inclusive lower and upper bound of valid values for the state. In any case, the information is merely a hint. It may be possible to have a state value outside of the hinted range and setting a value within the range may fail. The return value (if non-NULL) should be freed with g_variant_unref() when it is no longer required. Since 2.28
Queries the current state of the named action within action_group. If the action is not stateful then NULL will be returned. If the action is stateful then the type of the return value is the type given by g_action_group_get_action_state_type(). The return value (if non-NULL) should be freed with g_variant_unref() when it is no longer required. Since 2.28
Request for the state of the named action within action_group to be changed to value. The action must be stateful and value must be of the correct type. See g_action_group_get_action_state_type(). This call merely requests a change. The action may refuse to change its state or may change its state to something other than value. See g_action_group_get_action_state_hint(). If the value GVariant is floating, it is consumed. Since 2.28
Activate the named action within action_group. If the action is expecting a parameter, then the correct type of parameter must be given as parameter. If the action is expecting no parameters then parameter must be NULL. See g_action_group_get_action_parameter_type(). Since 2.28
Emits the "action-added" signal on action_group. This function should only be called by GActionGroup implementations. Since 2.28
Emits the "action-removed" signal on action_group. This function should only be called by GActionGroup implementations. Since 2.28
Emits the "action-enabled-changed" signal on action_group. This function should only be called by GActionGroup implementations. Since 2.28
Emits the "action-state-changed" signal on action_group. This function should only be called by GActionGroup implementations. Since 2.28 Signal Details The "action-added" signal void user_function (GActionGroup *action_group, gchar *action_name, gpointer user_data) : Has Details Signals that a new action was just added to the group. This signal is emitted after the action has been added and is now visible. Since 2.28
the main Gtk struct as a void*
Looks up the action with the name action_name in action_map. If no such action exists, returns NULL. Since 2.32
A convenience function for creating multiple GSimpleAction instances and adding them to a GActionMap. Each action is constructed as per one GActionEntry. Since 2.32
Adds an action to the action_map. If the action map already contains an action with the same name as action then the old action is dropped from the action map. The action map takes its own reference on action. Since 2.32
Removes the named action from the action map. If no action of this name is in the map then nothing happens. Since 2.32
A GApplication is the foundation of an application. It wraps some low-level platform-specific services and is intended to act as the foundation for higher-level application classes such as GtkApplication or MxApplication. In general, you should not use this class outside of a higher level framework.
GApplication provides convenient life cycle management by maintaining a use count for the primary application instance. The use count can be changed using g_application_hold() and g_application_release(). If it drops to zero, the application exits. Higher-level classes such as GtkApplication employ the use count to ensure that the application stays alive as long as it has any opened windows.
Another feature that GApplication (optionally) provides is process uniqueness. Applications can make use of this functionality by providing a unique application ID. If given, only one application with this ID can be running at a time per session. The session concept is platform-dependent, but corresponds roughly to a graphical desktop login. When your application is launched again, its arguments are passed through platform communication to the already running program. The already running instance of the program is called the primary instance; for non-unique applications this is the always the current instance. On Linux, the D-Bus session bus is used for communication.
The use of GApplication differs from some other commonly-used uniqueness libraries (such as libunique) in important ways. The application is not expected to manually register itself and check if it is the primary instance. Instead, the main() function of a GApplication should do very little more than instantiating the application instance, possibly connecting signal handlers, then calling g_application_run(). All checks for uniqueness are done internally. If the application is the primary instance then the startup signal is emitted and the mainloop runs. If the application is not the primary instance then a signal is sent to the primary instance and g_application_run() promptly returns. See the code examples below.
If used, the expected form of an application identifier is very close to that of of a DBus bus name. Examples include: "com.example.MyApp", "org.example.internal-apps.Calculator". For details on valid application identifiers, see g_application_id_is_valid().
On Linux, the application identifier is claimed as a well-known bus name on the user's session bus. This means that the uniqueness of your application is scoped to the current session. It also means that your application may provide additional services (through registration of other object paths) at that bus name. The registration of these object paths should be done with the shared GDBus session bus. Note that due to the internal architecture of GDBus, method calls can be dispatched at any time (even if a main loop is not running). For this reason, you must ensure that any object paths that you wish to register are registered before GApplication attempts to acquire the bus name of your application (which happens in g_application_register()). Unfortunately, this means that you cannot use g_application_get_is_remote() to decide if you want to register object paths.
GApplication also implements the GActionGroup and GActionMap interfaces and lets you easily export actions by adding them with g_action_map_add_action(). When invoking an action by calling g_action_group_activate_action() on the application, it is always invoked in the primary instance. The actions are also exported on the session bus, and GIO provides the GDBusActionGroup wrapper to conveniently access them remotely. GIO provides a GDBusMenuModel wrapper for remote access to exported GMenuModels.
There is a number of different entry points into a GApplication:
via 'Activate' (i.e. just starting the application) via 'Open' (i.e. opening some files) by handling a command-line via activating an action
The "startup" signal lets you handle the application initialization for all of these in a single place.
Regardless of which of these entry points is used to start the application, GApplication passes some platform data from the launching instance to the primary instance, in the form of a GVariant dictionary mapping strings to variants. To use platform data, override the before_emit or after_emit virtual functions in your GApplication subclass. When dealing with GApplicationCommandLine objects, the platform data is directly available via g_application_command_line_get_cwd(), g_application_command_line_get_environ() and g_application_command_line_get_platform_data().
As the name indicates, the platform data may vary depending on the operating system, but it always includes the current directory (key "cwd"), and optionally the environment (ie the set of environment variables and their values) of the calling process (key "environ"). The environment is only added to the platform data if the G_APPLICATION_SEND_ENVIRONMENT flag is set. GApplication subclasses can add their own platform data by overriding the add_platform_data virtual function. For instance, GtkApplication adds startup notification data in this way.
To parse commandline arguments you may handle the "command-line" signal or override the local_command_line() vfunc, to parse them in either the primary instance or the local instance, respectively.