class: GClosure

[42:7] extends: object

A GClosure 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][struct@Value] into a suitable form, perform the callback on the converted arguments, and transform the return value back into a [struct@Value]. 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 [struct@Value] and native C types. The GObject library provides the [struct@CClosure] type for this purpose. Bindings for other languages need marshallers which convert between [GValues][struct@Value] and suitable representations in the runtime of the language in order to use functions written in that language as callbacks. Use [method@Closure.set_marshal] 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 [func@signal_new] 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 [func@signal_connect_closure], 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 [struct@Closure] 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. - [method@Closure.invalidate] and invalidation notifiers allow callbacks to be automatically removed when the objects they point to go away.

Members

handleObj
lib
retainedCallbacks
signalHandlerNames
signalSetterHandlers

Methods

GClosure (sizeof_closure = null, object = null)

A variant of g_closure_new_simple() which stores @object in the @data field of the closure and calls g_object_watch_closure() on @object and the created closure. This function is mainly useful when implementing new types of closures.
- @p sizeof_closure is the size of the structure to allocate, must be at least sizeof (GClosure).
- @p object is a #GObject pointer to store in the @data field of the newly allocated #GClosure.
toNativeHandle (Source)

Normalizes a constructor argument into a raw pointer carrier. Accepts a raw NativeHandle, a raw NativeBuffer returned from fn.call(...), another generated wrapper exposing handle(), or null. Returns null when the argument carries no pointer.
- @p Source is the raw handle, raw buffer, wrapper, or null.
- @r A raw pointer carrier or null when no pointer is present.
getLib ()

Returns the opened native library for this generated wrapper.
- @r The opened native library.
handle ()

Returns the wrapped NativeHandle.
- @r The wrapped NativeHandle.
isNull ()

Returns true when the wrapped handle is null.
- @r A bool.
describe ()

Returns a small string for debugging generated wrappers.
- @r A string.
add_finalize_notifier (notify_data, object notify_func)

Registers a finalization notifier which will be called when the reference count of @closure goes down to 0. Multiple finalization notifiers on a single closure are invoked in unspecified order. If a single call to g_closure_unref() results in the closure being both invalidated and finalized, then the invalidate notifiers will be run before the finalize notifiers.
- @p notify_data is data to pass to @notify_func.
- @p notify_func is the callback function to register.
- @r None.
add_invalidate_notifier (notify_data, object notify_func)

Registers an invalidation notifier which will be called when the @closure is invalidated with g_closure_invalidate(). Invalidation notifiers are invoked before finalization notifiers, in an unspecified order.
- @p notify_data is data to pass to @notify_func.
- @p notify_func is the callback function to register.
- @r None.
add_marshal_guards (pre_marshal_data, post_marshal_data, object post_marshal_notify)

Adds a pair of notifiers which get invoked before and after the closure callback, respectively. This is typically used to protect the extra arguments for the duration of the callback. See g_object_watch_closure() for an example of marshal guards.
- @p pre_marshal_data is data to pass to @pre_marshal_notify.
- @p pre_marshal_notify is a function to call before the closure callback.
- @p post_marshal_data is data to pass to @post_marshal_notify.
- @p post_marshal_notify is a function to call after the closure callback.
- @r None.
invalidate ()

Sets a flag on the closure to indicate that its calling environment has become invalid, and thus causes any future invocations of g_closure_invoke() on this @closure to be ignored. Also, invalidation notifiers installed on the closure will be called at this point. Note that unless you are holding a reference to the closure yourself, the invalidation notifiers may unref the closure and cause it to be destroyed, so if you need to access the closure after calling g_closure_invalidate(), make sure that you've previously called g_closure_ref(). Note that g_closure_invalidate() will also be called when the reference count of a closure drops to zero (unless it has already been invalidated before).
- @r None.
ref ()

Increments the reference count on a closure to force it staying alive while the caller holds a pointer to it.
- @r The @closure passed in, for convenience.
remove_finalize_notifier (notify_data, object notify_func)

Removes a finalization notifier. Notice that notifiers are automatically removed after they are run.
- @p notify_data is data which was passed to g_closure_add_finalize_notifier() when registering @notify_func.
- @p notify_func is the callback function to remove.
- @r None.
remove_invalidate_notifier (notify_data, object notify_func)

Removes an invalidation notifier. Notice that notifiers are automatically removed after they are run.
- @p notify_data is data which was passed to g_closure_add_invalidate_notifier() when registering @notify_func.
- @p notify_func is the callback function to remove.
- @r None.
set_marshal (object marshal)

Sets the marshaller of @closure. The marshal_data of @marshal provides a way for a meta marshaller to provide additional information to the marshaller. For GObject's C predefined marshallers (the g_cclosure_marshal_*() functions), what it provides is a callback function to use instead of @closure->callback. See also: g_closure_set_meta_marshal()
- @p marshal is a #GClosureMarshal function.
- @r None.
set_meta_marshal (marshal_data, object meta_marshal)

Sets the meta marshaller of @closure. A meta marshaller wraps the
- @closure's marshal and modifies the way it is called in some fashion. The most common use of this facility is for C callbacks. The same marshallers (generated by [glib-genmarshal][glib-genmarshal]), are used everywhere, but the way that we get the callback function differs. In most cases we want to use the @closure's callback, but in other cases we want to use some different technique to retrieve the callback function. For example, class closures for signals (see g_signal_type_cclosure_new()) retrieve the callback function from a fixed offset in the class structure. The meta marshaller retrieves the right callback and passes it to the marshaller as the @marshal_data argument.
- @p marshal_data is context-dependent data to pass to @meta_marshal.
- @p meta_marshal is a #GClosureMarshal function.
- @r None.
sink ()

Takes over the initial ownership of a closure. Each closure is initially created in a "floating" state, which means that the initial reference count is not owned by any caller. This function checks to see if the object is still floating, and if so, unsets the floating state and decreases the reference count. If the closure is not floating, g_closure_sink() does nothing. The reason for the existence of the floating state is to prevent cumbersome code sequences like: |[ closure = g_cclosure_new (cb_func, cb_data); g_source_set_closure (source, closure); g_closure_unref (closure); // GObject doesn't really need this ]| Because g_source_set_closure() (and similar functions) take ownership of the initial reference count, if it is unowned, we instead can write: |[ g_source_set_closure (source, g_cclosure_new (cb_func, cb_data)); ]| Generally, this function is used together with g_closure_ref(). An example of storing a closure for later notification looks like: |[ static GClosure *notify_closure = NULL; void foo_notify_set_closure (GClosure *closure) { if (notify_closure) g_closure_unref (notify_closure); notify_closure = closure; if (notify_closure) { g_closure_ref (notify_closure); g_closure_sink (notify_closure); } } ]| Because g_closure_sink() may decrement the reference count of a closure (if it hasn't been called on @closure yet) just like g_closure_unref(), g_closure_ref() should be called prior to this function.
- @r None.
unref ()

Decrements the reference count of a closure after it was previously incremented by the same caller. If no other callers are using the closure, then the closure will be destroyed and freed.
- @r None.

class: GClosureCtors

[318:14] static extends: object

Alternate constructors for GClosure. Usage: GClosureCtors.<name>(...). The primary constructor lives directly on GClosure.

Methods

newSimple (int sizeof_closure, data)

Allocates a struct of the given size and initializes the initial part as a #GClosure. This function is mainly useful when implementing new types of closures: |[ typedef struct _MyClosure MyClosure; struct _MyClosure { GClosure closure; // extra data goes here }; static void my_closure_finalize (gpointer notify_data, GClosure *closure) { MyClosure *my_closure = (MyClosure *)closure; // free extra data here } MyClosure *my_closure_new (gpointer data) { GClosure *closure; MyClosure *my_closure; closure = g_closure_new_simple (sizeof (MyClosure), data); my_closure = (MyClosure *) closure; // initialize extra data here g_closure_add_finalize_notifier (closure, notify_data, my_closure_finalize); return my_closure; } ]|
- @p sizeof_closure is the size of the structure to allocate, must be at least sizeof (GClosure).
- @p data is data to store in the @data field of the newly allocated #GClosure.
- @r A new GClosure.