Package ch.bailu.gtk.gobject

Interface TypeInfo.OnClassInitFunc

Enclosing class:

TypeInfo

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public static interface TypeInfo.OnClassInitFunc

Method Summary

Modifier and Type	Method	Description
void	onClassInitFunc(CallbackHandler __self, Pointer g_class, Pointer class_data)	A callback function used by the type system to initialize the class of a specific type.

Method Details

onClassInitFunc

void onClassInitFunc(CallbackHandler __self,
 @Nonnull
 Pointer g_class,
 @Nullable
 Pointer class_data)

A callback function used by the type system to initialize the class
of a specific type.

This function should initialize all static class members.

The initialization process of a class involves:

- Copying common members from the parent class over to the
derived class structure.
- Zero initialization of the remaining members not copied
over from the parent class.
- Invocation of the GBaseInitFunc() initializers of all parent
types and the class' type.
- Invocation of the class' GClassInitFunc() initializer.

Since derived classes are partially initialized through a memory copy
of the parent class, the general rule is that GBaseInitFunc() and
GBaseFinalizeFunc() should take care of necessary reinitialization
and release of those class members that were introduced by the type
that specified these GBaseInitFunc()/GBaseFinalizeFunc().
GClassInitFunc() should only care about initializing static
class members, while dynamic class members (such as allocated strings
or reference counted resources) are better handled by a GBaseInitFunc()
for this type, so proper initialization of the dynamic class members
is performed for class initialization of derived types as well.

An example may help to correspond the intend of the different class
initializers:

<!-- language="C" -->
 typedef struct {
   GObjectClass parent_class;
   gint         static_integer;
   gchar       *dynamic_string;
 } TypeAClass;
 static void
 type_a_base_class_init (TypeAClass *class)
 {
   class->dynamic_string = g_strdup ("some string");
 }
 static void
 type_a_base_class_finalize (TypeAClass *class)
 {
   g_free (class->dynamic_string);
 }
 static void
 type_a_class_init (TypeAClass *class)
 {
   class->static_integer = 42;
 }
 
 typedef struct {
   TypeAClass   parent_class;
   gfloat       static_float;
   GString     *dynamic_gstring;
 } TypeBClass;
 static void
 type_b_base_class_init (TypeBClass *class)
 {
   class->dynamic_gstring = g_string_new ("some other string");
 }
 static void
 type_b_base_class_finalize (TypeBClass *class)
 {
   g_string_free (class->dynamic_gstring);
 }
 static void
 type_b_class_init (TypeBClass *class)
 {
   class->static_float = 3.14159265358979323846;
 }
 

Initialization of TypeBClass will first cause initialization of
TypeAClass (derived classes reference their parent classes, see
g_type_class_ref() on this).

Initialization of TypeAClass roughly involves zero-initializing its fields,
then calling its GBaseInitFunc() type_a_base_class_init() to allocate
its dynamic members (dynamic_string), and finally calling its GClassInitFunc()
type_a_class_init() to initialize its static members (static_integer).
The first step in the initialization process of TypeBClass is then
a plain memory copy of the contents of TypeAClass into TypeBClass and
zero-initialization of the remaining fields in TypeBClass.
The dynamic members of TypeAClass within TypeBClass now need
reinitialization which is performed by calling type_a_base_class_init()
with an argument of TypeBClass.

After that, the GBaseInitFunc() of TypeBClass, type_b_base_class_init()
is called to allocate the dynamic members of TypeBClass (dynamic_gstring),
and finally the GClassInitFunc() of TypeBClass, type_b_class_init(),
is called to complete the initialization process with the static members
(static_float).

Corresponding finalization counter parts to the GBaseInitFunc() functions
have to be provided to release allocated resources at class finalization
time.

Parameters:

g_class - The #GTypeClass structure to initialize.

class_data - The @class_data member supplied via the #GTypeInfo structure.