Closure

class Closure(*args, **kwargs)

Constructors:

Closure()
new_object(sizeof_closure:int, object:GObject.Object) -> GObject.Closure
new_simple(sizeof_closure:int, data=None) -> GObject.Closure

Constructors

class Closure

classmethod new_object(sizeof_closure: int, object: Object) → Callable[[...], Any]

A variant of new_simple() which stores object in the data field of the closure and calls watch_closure() on object and the created closure. This function is mainly useful when implementing new types of closures.

Parameters:

sizeof_closure – the size of the structure to allocate, must be at least sizeof (GClosure)
object – a Object pointer to store in the data field of the newly allocated Closure

classmethod new_simple(sizeof_closure: int, data: None) → Callable[[...], Any]

Allocates a struct of the given size and initializes the initial part as a Closure.

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;
}

Parameters:

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 Closure

Methods

class Closure

invalidate() → None

Sets a flag on the closure to indicate that its calling environment has become invalid, and thus causes any future invocations of 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 invalidate(), make sure that you’ve previously called ref().

Note that invalidate() will also be called when the reference count of a closure drops to zero (unless it has already been invalidated before).

invoke(param_values: Sequence[Any], invocation_hint: None) → Any

Invokes the closure, i.e. executes the callback represented by the closure.

Parameters:

param_values – an array of Value holding the arguments on which to invoke the callback of closure
invocation_hint – a context-dependent invocation hint

sink() → None

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, 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 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 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 sink() may decrement the reference count of a closure (if it hasn’t been called on closure yet) just like unref(), ref() should be called prior to this function.

Fields

class Closure

data

derivative_flag

floating

in_inotify

in_marshal: Indicates whether the closure is currently being invoked with invoke()

is_invalid: Indicates whether the closure has been invalidated by invalidate()

marshal

meta_marshal_nouse

n_fnotifiers

n_guards

n_inotifiers

notifiers

ref_count