Gnome::GObject::Closure

Functions as first-class objects

Description

A Gnome::GObject::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 Gnome::GObject::Values into a suitable form, perform the callback on the converted arguments, and transform the return value back into a Gnome::GObject::Value.

Note: This module is kept very simple because Raku does not need an implementation of a closure in C, which Raku can do that very neatly. So this closure is only created to provide a callback which is needed in some cases. The other items provided in the C closure class like controlling the marshaller, providing data to the closure, the destroy function for that data, etcetera, is not supported by the Raku module.

Synopsis

Declaration

unit class Gnome::GObject::Closure;
also is Gnome::GObject::Boxed;

Example

The following example is translated from the example here. It shows an empty window where you can type two control commands <ctrl>A and <ctrl><shift>C . The first shows a message on the console and the second stops the program.

use v6;

use Gnome::GObject::Closure;

use Gnome::Gtk3::Window;
use Gnome::Gtk3::Main;
use Gnome::Gtk3::AccelGroup;

use Gnome::Gdk3::Types;
use Gnome::Gdk3::Keysyms;


class CTest {
  method accelerator-pressed ( Str :$arg1 ) {
    note "accelerator pressed, user argument = '$arg1'";
  }

  method stop-test ( ) {
    note "program stopped";
    Gnome::Gtk3::Main.new.quit;
  }
}

my CTest $ctest .= new;


with my Gnome::Gtk3::AccelGroup $accel-group .= new {
  .connect(
    GDK_KEY_A, GDK_CONTROL_MASK, 0,
    Gnome::GObject::Closure.new(
      :handler-object($ctest), :handler-name<accelerator-pressed>,
      :handler-opts(:arg1<'foo'>)
    )
  );

  .connect(
    GDK_KEY_C, GDK_CONTROL_MASK +| GDK_SHIFT_MASK, 0,
    Gnome::GObject::Closure.new(
      :handler-object($ctest), :handler-name<stop-test>
    )
  );
}

with my Gnome::Gtk3::Window $window .= new {
  .add-accel-group($accel-group);
  .register-signal( $ctest, 'stop-test', 'destroy');
  .show;
}

Gnome::Gtk3::Main.new.main;

Types

Methods

new

:handler-object, :handler-name

Create a new Closure object. Minimizing the Closure to only setting of a callback method. The $handler-name is the method which is defined in the user object $handler-object. Optionally the user can provide some arguments to the handler.

multi method new (
  Any:D :$handler-object!, Str:D :$handler-name!,
  :%handler-opts
)

:native-object

Create a Closure object using a native object from elsewhere. See also Gnome::N::TopLevelClassSupport.

multi method new ( N-GObject :$native-object! )

invalidate

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 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).

method invalidate ( )