Glib::ExtraClassInit Class Reference

A convenience class for named custom types. More...

#include <glibmm/extraclassinit.h>

Inheritance diagram for Glib::ExtraClassInit:

Protected Member Functions
	ExtraClassInit (GClassInitFunc class_init_func, void *class_data=nullptr, GInstanceInitFunc instance_init_func=nullptr)
	Constructor.
Protected Member Functions inherited from Glib::ObjectBase
	ObjectBase ()
	This default constructor is called implicitly from the constructor of user-derived classes, even if, for instance, Gtk::Button calls a different ObjectBase constructor.
	ObjectBase (const char *custom_type_name)
	A derived constructor always overrides this choice.
	ObjectBase (const std::type_info &custom_type_info)
	This constructor is a special feature to allow creation of derived types on the fly, without having to use g_object_new() manually.
	ObjectBase (ObjectBase &&src) noexcept
ObjectBase &	operator= (ObjectBase &&src) noexcept
virtual	~ObjectBase () noexcept=0
void	initialize (GObject *castitem)
void	initialize_move (GObject *castitem, Glib::ObjectBase *previous_wrapper)

Additional Inherited Members
Public Member Functions inherited from Glib::ObjectBase
	ObjectBase (const ObjectBase &)=delete
ObjectBase &	operator= (const ObjectBase &)=delete
void	set_property_value (const Glib::ustring & property_name, const Glib::ValueBase & value)
	You probably want to use a specific property_*() accessor method instead.
void	get_property_value (const Glib::ustring & property_name, Glib::ValueBase & value) const
	You probably want to use a specific property_*() accessor method instead.
template<class PropertyType >
void	set_property (const Glib::ustring & property_name, const PropertyType & value)
	You probably want to use a specific property_*() accessor method instead.
template<class PropertyType >
void	get_property (const Glib::ustring & property_name, PropertyType & value) const
	You probably want to use a specific property_*() accessor method instead.
template<class PropertyType >
PropertyType	get_property (const Glib::ustring & property_name) const
	You probably want to use a specific property_*() accessor method instead.
sigc::connection	connect_property_changed (const Glib::ustring & property_name, const sigc::slot< void()> &slot)
	You can use the signal_changed() signal of the property proxy instead.
sigc::connection	connect_property_changed (const Glib::ustring & property_name, sigc::slot< void()> &&slot)
	You can use the signal_changed() signal of the property proxy instead.
void	freeze_notify ()
	Increases the freeze count on object.
void	thaw_notify ()
	Reverts the effect of a previous call to freeze_notify().
virtual void	reference () const
	Increment the reference count for this object.
virtual void	unreference () const
	Decrement the reference count for this object.
GObject *	gobj ()
	Provides access to the underlying C GObject.
const GObject *	gobj () const
	Provides access to the underlying C GObject.
GObject *	gobj_copy () const
	Give a ref-ed copy to someone. Use for direct struct access.

Detailed Description

A convenience class for named custom types.

Use it if you need to add code to GType's class init function and/or need an instance init function. Example:

#include <glibmm/extraclassinit.h>
 
extern "C"
{
// Extra class init function.
static void my_extra_class_init_function(void* g_class, void* class_data)
{
  g_return_if_fail(GTK_IS_WIDGET_CLASS(g_class));
 
  const auto klass = static_cast<GtkWidgetClass*>(g_class);
  const auto css_name = static_cast<Glib::ustring*>(class_data);
 
  gtk_widget_class_set_css_name(klass, css_name->c_str());
}
 
// Extra instance init function.
static void my_instance_init_function(GTypeInstance* instance, void* g_class)
{
  g_return_if_fail(GTK_IS_WIDGET(instance));
 
  // Nothing to do here.
  // This extra instance init function just shows how such a function can
  // be added to a custom widget, if necessary.
}
} // extern "C"
 
class MyExtraInit : public Glib::ExtraClassInit
{
public:
  MyExtraInit(const Glib::ustring& css_name)
  :
  Glib::ExtraClassInit(my_extra_class_init_function, &m_css_name, my_instance_init_function),
  m_css_name(css_name)
  { }
 
private:
  Glib::ustring m_css_name;
};
 
class MyWidget : public MyExtraInit, public Gtk::Widget
{
public:
  MyWidget()
  :
  // The GType name will be gtkmm__CustomObject_MyWidget
  Glib::ObjectBase("MyWidget"), // Unique class name
  MyExtraInit("my-widget"),
  Gtk::Widget()
  {
    // ...
  }
  // ...
};

The callback functions (my_extra_class_init_function() and my_instance_init_function() in the example) are called from GLib (a C library). They shall have C linkage. (Many compilers accept callback functions with C++ linkage, but such a program has undefined behavior.)

If you want the functions with C linkage to have internal linkage, they must be declared 'static', even if they are defined in an anonymous namespace. The compiler respects namespace declarations of functions with C linkage, but the linker does not.

Note

Classes derived from ExtraClassInit (MyExtraInit in the example) must be listed before Glib::Object or a class derived from Glib::Object (Gtk::Widget in the example) in the list of base classes.

Since glibmm 2.58:

Constructor & Destructor Documentation

ExtraClassInit()

Glib::ExtraClassInit::ExtraClassInit ( GClassInitFunc  class_init_func, void *  class_data = nullptr, GInstanceInitFunc  instance_init_func = nullptr  )

explicitprotected

Constructor.

Parameters

class_init_func	Pointer to an extra class init function. nullptr, if no extra class init function is needed.
class_data	Class data pointer, passed to the class init function. Can be nullptr, if the class init function does not need it.
instance_init_func	Pointer to an instance init function. nullptr, if no instance init function is needed.