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#ifndef _GLIBMM_EXTRACLASSINIT_H
#define _GLIBMM_EXTRACLASSINIT_H
/* Copyright (C) 2017 The glibmm Development Team
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
*/
#include <glibmm/objectbase.h>
namespace Glib
{
/** 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:
* @code
* #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()
* {
* // ...
* }
* // ...
* };
* @endcode
*
* 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.
*
* @newin{2,58}
*/
class GLIBMM_API ExtraClassInit : virtual public ObjectBase
{
protected:
/** Constructor.
*
* @param class_init_func Pointer to an extra class init function.
* nullptr, if no extra class init function is needed.
* @param class_data Class data pointer, passed to the class init function.
* Can be nullptr, if the class init function does not need it.
* @param instance_init_func Pointer to an instance init function.
* nullptr, if no instance init function is needed.
*/
explicit ExtraClassInit(GClassInitFunc class_init_func, void* class_data = nullptr,
GInstanceInitFunc instance_init_func = nullptr);
};
} // namespace Glib
#endif /* _GLIBMM_EXTRACLASSINIT_H */
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