Package org.gnome.gobject

Interface ClassInitFunc

All Superinterfaces:

FunctionPointer

Functional Interface:

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

@FunctionalInterface
@Generated("io.github.jwharm.JavaGI")
public interface ClassInitFunc
extends FunctionPointer

Functional interface declaration of the ClassInitFunc callback.

See Also:

• run(org.gnome.gobject.TypeClass, java.lang.foreign.MemorySegment)

Method Summary

Modifier and Type	Method	Description
void	run(TypeClass gClass, @Nullable MemorySegment classData)	A callback function used by the type system to initialize the class of a specific type.
default MemorySegment	toCallback(Arena arena)	Creates a native function pointer to the upcall(java.lang.foreign.MemorySegment, java.lang.foreign.MemorySegment) method.
default void	upcall(MemorySegment gClass, MemorySegment classData)	The upcall method is called from native code.

Method Details

run

void run(TypeClass gClass,
 @Nullable
 @Nullable MemorySegment classData)

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:

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.

upcall

default void upcall(MemorySegment gClass,
 MemorySegment classData)

The upcall method is called from native code. The parameters are marshaled and run(org.gnome.gobject.TypeClass, java.lang.foreign.MemorySegment) is executed.

toCallback

default MemorySegment toCallback(Arena arena)

Creates a native function pointer to the upcall(java.lang.foreign.MemorySegment, java.lang.foreign.MemorySegment) method.

Specified by:

toCallback in interface FunctionPointer

Parameters:

arena - the function pointer will be allocated in this arena

Returns:

the native function pointer