gobject.Closure.Closure Class Reference

List of all members.

Detailed Description

Description 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 reponsibility 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 languages as callbacks. Within GObject, closures play an important role in the implementation of signals. When a signal is registered, the c_marshaller argument to g_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 utility. Closures can be explicitly connected to signals with g_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 GClosure makes it easy to handle reentrancy right; if a callback is removed while it is being invoked, the closure and it's parameters won't be freed until the invocation finishes. g_closure_invalidate() and invalidation notifiers allow callbacks to be automatically removed when the objects they point to go away.


Public Member Functions

GClosuregetClosureStruct ()
 this (GClosure *gClosure)
 Sets our main struct and passes it to the parent class.
 this (uint sizeofClosure, ObjectG object)
 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.
Closure ref ()
 Increments the reference count on a closure to force it staying alive while the caller holds a pointer to it.
void sink ()
 Takes over the initial ownership of a closure.
void unref ()
 Decrements the reference count of a closure after it was previously incremented by the same caller.
void invoke (Value returnValue, uint nParamValues, Value paramValues, void *invocationHint)
 Invokes the closure, i.e.
void invalidate ()
 Sets a flag on the closure to indicate that it's calling environment has become invalid, and thus causes any future invocations of g_closure_invoke() on this closure to be ignored.
void addFinalizeNotifier (void *notifyData, GClosureNotify notifyFunc)
 Registers a finalization notifier which will be called when the reference count of closure goes down to 0.
void addInvalidateNotifier (void *notifyData, GClosureNotify notifyFunc)
 Registers an invalidation notifier which will be called when the closure is invalidated with g_closure_invalidate().
void removeFinalizeNotifier (void *notifyData, GClosureNotify notifyFunc)
 Removes a finalization notifier.
void removeInvalidateNotifier (void *notifyData, GClosureNotify notifyFunc)
 Removes a invalidation notifier.
 this (uint sizeofClosure, void *data)
 Allocates a struct of the given size and initializes the initial part as a GClosure.
void setMarshal (GClosureMarshal marshal)
 Sets the marshaller of closure.
void addMarshalGuards (void *preMarshalData, GClosureNotify preMarshalNotify, void *postMarshalData, GClosureNotify postMarshalNotify)
 Adds a pair of notifiers which get invoked before and after the closure callback, respectively.
void setMetaMarshal (void *marshalData, GClosureMarshal metaMarshal)
 Sets the meta marshaller of closure.

Static Public Member Functions

static void gSourceSetClosure (Source source, Closure closure)
 Set the callback for a source as a GClosure.

Protected Member Functions

void * getStruct ()
 the main Gtk struct as a void*

Protected Attributes

GClosuregClosure
 the main Gtk struct


Constructor & Destructor Documentation

gobject.Closure.Closure.this ( GClosure gClosure  ) 

Sets our main struct and passes it to the parent class.

gobject.Closure.Closure.this ( uint  sizeofClosure,
ObjectG  object 
)

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. sizeof_closure: the size of the structure to allocate, must be at least sizeof (GClosure) object: a GObject pointer to store in the data field of the newly allocated GClosure Returns: a newly allocated GClosure

gobject.Closure.Closure.this ( uint  sizeofClosure,
void *  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; } sizeof_closure: the size of the structure to allocate, must be at least sizeof (GClosure) data: data to store in the data field of the newly allocated GClosure Returns: a newly allocated GClosure


Member Function Documentation

void gobject.Closure.Closure.addFinalizeNotifier ( void *  notifyData,
GClosureNotify  notifyFunc 
)

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. closure: a GClosure notify_data: data to pass to notify_func notify_func: the callback function to register

void gobject.Closure.Closure.addInvalidateNotifier ( void *  notifyData,
GClosureNotify  notifyFunc 
)

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. closure: a GClosure notify_data: data to pass to notify_func notify_func: the callback function to register

void gobject.Closure.Closure.addMarshalGuards ( void *  preMarshalData,
GClosureNotify  preMarshalNotify,
void *  postMarshalData,
GClosureNotify  postMarshalNotify 
)

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. closure: a GClosure pre_marshal_data: data to pass to pre_marshal_notify pre_marshal_notify: a function to call before the closure callback post_marshal_data: data to pass to post_marshal_notify post_marshal_notify: a function to call after the closure callback

GClosure* gobject.Closure.Closure.getClosureStruct (  ) 

void* gobject.Closure.Closure.getStruct (  )  [protected]

the main Gtk struct as a void*

static void gobject.Closure.Closure.gSourceSetClosure ( Source  source,
Closure  closure 
) [static]

Set the callback for a source as a GClosure.

If the source is not one of the standard GLib types, the closure_callback and closure_marshal fields of the GSourceFuncs structure must have been filled in with pointers to appropriate functions. source: the source closure: a GClosure

void gobject.Closure.Closure.invalidate (  ) 

Sets a flag on the closure to indicate that it's 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). closure: GClosure to invalidate

void gobject.Closure.Closure.invoke ( Value  returnValue,
uint  nParamValues,
Value  paramValues,
void *  invocationHint 
)

Invokes the closure, i.e.

executes the callback represented by the closure. closure: a GClosure return_value: a GValue to store the return value. May be NULL if the callback of closure doesn't return a value. n_param_values: the length of the param_values array param_values: an array of GValues holding the arguments on which to invoke the callback of closure invocation_hint: a context-dependent invocation hint

Closure gobject.Closure.Closure.ref (  ) 

Increments the reference count on a closure to force it staying alive while the caller holds a pointer to it.

closure: GClosure to increment the reference count on Returns: The closure passed in, for convenience

void gobject.Closure.Closure.removeFinalizeNotifier ( void *  notifyData,
GClosureNotify  notifyFunc 
)

Removes a finalization notifier.

Notifiers are automatically removed after they are run. closure: a GClosure notify_data: data which was passed to g_closure_add_finalize_notifier() when registering notify_func notify_func: the callback function to remove

void gobject.Closure.Closure.removeInvalidateNotifier ( void *  notifyData,
GClosureNotify  notifyFunc 
)

Removes a invalidation notifier.

Notifiers are automatically removed after they are run. closure: a GClosure notify_data: data which was passed to g_closure_add_invalidate_notifier() when registering notify_func notify_func: the callback function to remove

void gobject.Closure.Closure.setMarshal ( GClosureMarshal  marshal  ) 

Sets the marshaller of closure.

The marshal_data provides a way for a meta marshaller to provide additional information to the marshaller. (See g_closure_set_meta_marshal().) For GObject's C predefined marshallers (the g_cclosure_marshal_*() functions), what it provides is a callback function to use instead of closure->callback. closure: a GClosure marshal: a GClosureMarshal function

void gobject.Closure.Closure.setMetaMarshal ( void *  marshalData,
GClosureMarshal  metaMarshal 
)

Sets the meta marshaller of closure.

A meta marshaller wraps closure->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) are used everywhere, but the way that we get the callback function differs. In most cases we want to use closure->callback, but in other cases we want to use use some different technique to retrieve the callbakc 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. closure: a GClosure marshal_data: context-dependent data to pass to meta_marshal meta_marshal: a GClosureMarshal function

void gobject.Closure.Closure.sink (  ) 

Takes over the initial ownership of a closure.

Each closure is initially created in afloating state, which means that the initial reference count is not owned by any caller. g_closure_sink() 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 existance 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); /+* XXX 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(). Ane 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. closure: GClosure to decrement the initial reference count on, if it's still being held

void gobject.Closure.Closure.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. closure: GClosure to decrement the reference count on


Member Data Documentation

GClosure* gobject.Closure.Closure.gClosure [protected]

the main Gtk struct


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