Closure

A gobject.closure.Closure represents a callback supplied by the programmer.

It will generally comprise a function of some kind and a marshaller used to call it. It is the responsibility of the marshaller to convert the arguments for the invocation from #GValues into a suitable form, perform the callback on the converted arguments, and transform the return value back into a #GValue.

In the case of C programs, a closure usually just holds a pointer to a function and maybe a data argument, and the marshaller converts between #GValue and native C types. The GObject library provides the #GCClosure type for this purpose. Bindings for other languages need marshallers which convert between #GValues and suitable representations in the runtime of the language in order to use functions written in that language as callbacks. Use gobject.closure.Closure.setMarshal to set the marshaller on such a custom closure implementation.

Within GObject, closures play an important role in the implementation of signals. When a signal is registered, the @c_marshaller argument to gobject.global.signalNew specifies the default C marshaller for any closure which is connected to this signal. GObject provides a number of C marshallers for this purpose, see the g_cclosure_marshal_*() functions. Additional C marshallers can be generated with the [glib-genmarshal][glib-genmarshal] utility. Closures can be explicitly connected to signals with gobject.global.signalConnectClosure, but it usually more convenient to let GObject create a closure automatically by using one of the g_signal_connect_*() functions which take a callback function/user data pair.

Using closures has a number of important advantages over a simple callback function/data pointer combination:

Closures allow the callee to get the types of the callback parameters, which means that language bindings don't have to write individual glue for each callback type.
The reference counting of #GClosure makes it easy to handle reentrancy right; if a callback is removed while it is being invoked, the closure and its parameters won't be freed until the invocation finishes.
gobject.closure.Closure.invalidate and invalidation notifiers allow callbacks to be automatically removed when the objects they point to go away.

class Closure : Boxed {

static gobject.closure.Closure newObject(uint sizeofClosure, gobject.object.ObjectG object);

static gobject.closure.Closure newSimple(uint sizeofClosure, void* data);

void invalidate();

void invoke(gobject.value.Value returnValue, gobject.value.Value[] paramValues, void* invocationHint);

void sink();

}

Members

Functions

invalidate void invalidate(): Sets a flag on the closure to indicate that its calling environment has become invalid, and thus causes any future invocations of gobject.closure.Closure.invoke on this closure to be ignored.
invoke void invoke(gobject.value.Value returnValue, gobject.value.Value[] paramValues, void* invocationHint): Invokes the closure, i.e. executes the callback represented by the closure.
sink void sink(): Takes over the initial ownership of a closure.

Static functions

newObject gobject.closure.Closure newObject(uint sizeofClosure, gobject.object.ObjectG object): A variant of gobject.closure.Closure.newSimple which stores object in the data field of the closure and calls gobject.object.ObjectG.watchClosure on object and the created closure. This function is mainly useful when implementing new types of closures.
newSimple gobject.closure.Closure newSimple(uint sizeofClosure, void* data): Allocates a struct of the given size and initializes the initial part as a #GClosure.

Inherited Members

From Boxed

cInstancePtr void* cInstancePtr;: Pointer to the C boxed value
getType GType getType(): Get the GType of this boxed type.
gType GType gType [@property getter]: Boxed GType property.
self Boxed self(): Convenience method to return this cast to a type. For use in D with statements.
copy_ void* copy_(): Make a copy of the wrapped C boxed data.
boxedCopy void* boxedCopy(void* cBoxed): Copy a C boxed value using g_boxed_copy.
boxedFree void boxedFree(void* cBoxed): Free a C boxed value using g_boxed_free.

gobject closure classes

Closure