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/*
* e-extension.c
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) version 3.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with the program; if not, see <http://www.gnu.org/licenses/>
*
*/
/**
* SECTION: e-extension
* @short_description: abstract base class for extensions
* @include: e-util/e-extension.h
*
* #EExtension provides a way to extend the functionality of objects
* that implement the #EExtensible interface. #EExtension subclasses
* can target a particular extensible object type. New instances of
* an extensible object type get paired with a new instance of each
* #EExtension subclass that targets the extensible object type.
*
* The first steps of writing a new extension are as follows:
*
* 1. Subclass #EExtension.
*
* 2. In the class initialization function, specify the #GType being
* extended. The #GType must implement the #EExtensible interface.
*
* 3. Register the extension's own #GType. If the extension is to
* be loaded dynamically using #GTypeModule, the type should be
* registered in the library module's e_module_load() function.
**/
#include "e-extension.h"
#define E_EXTENSION_GET_PRIVATE(obj) \
(G_TYPE_INSTANCE_GET_PRIVATE \
((obj), E_TYPE_EXTENSION, EExtensionPrivate))
struct _EExtensionPrivate {
gpointer extensible; /* weak pointer */
};
enum {
PROP_0,
PROP_EXTENSIBLE
};
G_DEFINE_ABSTRACT_TYPE (
EExtension,
e_extension,
G_TYPE_OBJECT)
static void
extension_set_extensible (EExtension *extension,
EExtensible *extensible)
{
EExtensionClass *class;
GType extensible_type;
g_return_if_fail (E_IS_EXTENSIBLE (extensible));
g_return_if_fail (extension->priv->extensible == NULL);
class = E_EXTENSION_GET_CLASS (extension);
extensible_type = G_OBJECT_TYPE (extensible);
/* Verify the EExtensible object is the type we want. */
if (!g_type_is_a (extensible_type, class->extensible_type)) {
g_warning ("%s is meant to extend %s but was given an %s",
G_OBJECT_TYPE_NAME (extension),
g_type_name (class->extensible_type),
g_type_name (extensible_type));
return;
}
extension->priv->extensible = extensible;
g_object_add_weak_pointer (
G_OBJECT (extensible), &extension->priv->extensible);
}
static void
extension_set_property (GObject *object,
guint property_id,
const GValue *value,
GParamSpec *pspec)
{
switch (property_id) {
case PROP_EXTENSIBLE:
extension_set_extensible (
E_EXTENSION (object),
g_value_get_object (value));
return;
}
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
}
static void
extension_get_property (GObject *object,
guint property_id,
GValue *value,
GParamSpec *pspec)
{
switch (property_id) {
case PROP_EXTENSIBLE:
g_value_set_object (
value, e_extension_get_extensible (
E_EXTENSION (object)));
return;
}
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
}
static void
extension_constructed (GObject *object)
{
/* This allows subclasses to chain up safely since GObject
* does not implement this method, and we might want to do
* something here in the future. */
}
static void
extension_dispose (GObject *object)
{
EExtensionPrivate *priv;
priv = E_EXTENSION_GET_PRIVATE (object);
if (priv->extensible != NULL) {
g_object_remove_weak_pointer (
G_OBJECT (priv->extensible), &priv->extensible);
priv->extensible = NULL;
}
/* Chain up to parent's dispose() method. */
G_OBJECT_CLASS (e_extension_parent_class)->dispose (object);
}
static void
e_extension_class_init (EExtensionClass *class)
{
GObjectClass *object_class;
g_type_class_add_private (class, sizeof (EExtensionPrivate));
object_class = G_OBJECT_CLASS (class);
object_class->set_property = extension_set_property;
object_class->get_property = extension_get_property;
object_class->constructed = extension_constructed;
object_class->dispose = extension_dispose;
g_object_class_install_property (
object_class,
PROP_EXTENSIBLE,
g_param_spec_object (
"extensible",
"Extensible Object",
"The object being extended",
E_TYPE_EXTENSIBLE,
G_PARAM_READWRITE |
G_PARAM_CONSTRUCT_ONLY));
}
static void
e_extension_init (EExtension *extension)
{
extension->priv = E_EXTENSION_GET_PRIVATE (extension);
}
/**
* e_extension_get_extensible:
* @extension: an #EExtension
*
* Returns the object that @extension extends.
*
* Returns: the object being extended
**/
EExtensible *
e_extension_get_extensible (EExtension *extension)
{
g_return_val_if_fail (E_IS_EXTENSION (extension), NULL);
return E_EXTENSIBLE (extension->priv->extensible);
}
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