| Top | |
|
|
|
GIOExtensionPoint provides a mechanism for modules to extend the functionality of the library or application that loaded it in an organized fashion.
An extension point is identified by a name, and it may optionally
require that any implementation must be of a certain type (or derived
thereof). Use g_io_extension_point_register() to register an
extension point, and g_io_extension_point_set_required_type() to
set a required type.
A module can implement an extension point by specifying the GType
that implements the functionality. Additionally, each implementation
of an extension point has a name, and a priority. Use
g_io_extension_point_implement() to implement an extension point.
1 2 3 4 5 |
GIOExtensionPoint *ep; // Register an extension point ep = g_io_extension_point_register ("my-extension-point"); g_io_extension_point_set_required_type (ep, MY_TYPE_EXAMPLE); |
1 2 3 4 5 6 |
// Implement an extension point G_DEFINE_TYPE (MyExampleImpl, my_example_impl, MY_TYPE_EXAMPLE) g_io_extension_point_implement ("my-extension-point", my_example_impl_get_type (), "my-example", 10); |
It is up to the code that registered the extension point how it uses the implementations that have been associated with it. Depending on the use case, it may use all implementations, or only the one with the highest priority, or pick a specific one by name.
To avoid opening all modules just to find out what extension points they implement, GIO makes use of a caching mechanism, see gio-querymodules. You are expected to run this command after installing a GIO module.
The GIO_EXTRA_MODULES environment variable can be used to
specify additional directories to automatically load modules
from. This environment variable has the same syntax as the
PATH. If two modules have the same base name in different
directories, then the latter one will be ignored. If additional
directories are specified GIO will load modules from the built-in
directory last.
const char *
g_io_extension_get_name (GIOExtension *extension);
Gets the name under which extension
was registered.
Note that the same type may be registered as extension for multiple extension points, under different names.
gint
g_io_extension_get_priority (GIOExtension *extension);
Gets the priority with which extension
was registered.
GType
g_io_extension_get_type (GIOExtension *extension);
Gets the type associated with extension
.
GIOExtension * g_io_extension_point_get_extension_by_name (GIOExtensionPoint *extension_point,const char *name);
Finds a GIOExtension for an extension point by name.
the GIOExtension for extension_point
that has the
given name, or NULL if there is no extension with that name.
[transfer none]
GList *
g_io_extension_point_get_extensions (GIOExtensionPoint *extension_point);
Gets a list of all extensions that implement this extension point. The list is sorted by priority, beginning with the highest priority.
a GList of GIOExtensions. The list is owned by GIO and should not be modified.
[element-type GIOExtension][transfer none]
GType
g_io_extension_point_get_required_type
(GIOExtensionPoint *extension_point);
Gets the required type for extension_point
.
the GType that all implementations must have, or G_TYPE_INVALID if the extension point has no required type
GIOExtension * g_io_extension_point_implement (const char *extension_point_name,GType type,const char *extension_name,gint priority);
Registers type
as extension for the extension point with name
extension_point_name
.
If type
has already been registered as an extension for this
extension point, the existing GIOExtension object is returned.
extension_point_name |
the name of the extension point |
|
type |
the GType to register as extension |
|
extension_name |
the name for the extension |
|
priority |
the priority for the extension |
GIOExtensionPoint *
g_io_extension_point_lookup (const char *name);
Looks up an existing extension point.
the GIOExtensionPoint, or NULL if there
is no registered extension point with the given name.
[transfer none]
GIOExtensionPoint *
g_io_extension_point_register (const char *name);
Registers an extension point.
the new GIOExtensionPoint. This object is owned by GIO and should not be freed.
[transfer none]
void g_io_extension_point_set_required_type (GIOExtensionPoint *extension_point,GType type);
Sets the required type for extension_point
to type
.
All implementations must henceforth have this type.
GTypeClass *
g_io_extension_ref_class (GIOExtension *extension);
Gets a reference to the class for the type that is
associated with extension
.
typedef struct _GIOExtension GIOExtension;
GIOExtension is an opaque data structure and can only be accessed using the following functions.
typedef struct _GIOExtensionPoint GIOExtensionPoint;
GIOExtensionPoint is an opaque data structure and can only be accessed using the following functions.