Indicates whether the closure is currently being invoked with g_closure_invoke()
Indicates whether the closure has been invalidated by g_closure_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).
Invokes the closure, i.e. executes the callback represented by the closure.
an array of #GValues holding the arguments on which to invoke the callback of closure
a context-dependent invocation hint
Increments the reference count on a closure to force it staying alive while the caller holds a pointer to it.
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.
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.
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.
the size of the structure to allocate, must be at least sizeof (GClosure)
a #GObject pointer to store in the data field of the newly allocated #GClosure
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;
}
the size of the structure to allocate, must be at least sizeof (GClosure)
data to store in the data field of the newly allocated #GClosure
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 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 g_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_marshallerargument 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][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 its 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.