GstChildProxy

GstChildProxy — Interface for multi child elements.

Synopsis

#include <gst/gst.h>

                    GstChildProxy;
struct              GstChildProxyInterface;
guint               gst_child_proxy_get_children_count  (GstChildProxy *parent);
GstObject *         gst_child_proxy_get_child_by_name   (GstChildProxy *parent,
                                                         const gchar *name);
GstObject *         gst_child_proxy_get_child_by_index  (GstChildProxy *parent,
                                                         guint index);
gboolean            gst_child_proxy_lookup              (GstObject *object,
                                                         const gchar *name,
                                                         GstObject **target,
                                                         GParamSpec **pspec);
void                gst_child_proxy_get_property        (GstObject *object,
                                                         const gchar *name,
                                                         GValue *value);
void                gst_child_proxy_get_valist          (GstObject *object,
                                                         const gchar *first_property_name,
                                                         va_list var_args);
void                gst_child_proxy_get                 (GstObject *object,
                                                         const gchar *first_property_name,
                                                         ...);
void                gst_child_proxy_set_property        (GstObject *object,
                                                         const gchar *name,
                                                         const GValue *value);
void                gst_child_proxy_set_valist          (GstObject *object,
                                                         const gchar *first_property_name,
                                                         va_list var_args);
void                gst_child_proxy_set                 (GstObject *object,
                                                         const gchar *first_property_name,
                                                         ...);
void                gst_child_proxy_child_added         (GstObject *object,
                                                         GstObject *child);
void                gst_child_proxy_child_removed       (GstObject *object,
                                                         GstObject *child);

Object Hierarchy

  GInterface
   +----GstChildProxy

Prerequisites

GstChildProxy requires GstObject.

Known Implementations

GstChildProxy is implemented by GstBin and GstPipeline.

Signals

  "child-added"                                    : Run First
  "child-removed"                                  : Run First

Description

This interface abstracts handling of property sets for elements with children. Imagine elements such as mixers or polyphonic generators. They all have multiple GstPad or some kind of voice objects. Another use case are container elements like GstBin. The element implementing the interface acts as a parent for those child objects.

By implementing this interface the child properties can be accessed from the parent element by using gst_child_proxy_get() and gst_child_proxy_set().

Property names are written as "child-name::property-name". The whole naming scheme is recursive. Thus "child1::child2::property" is valid too, if "child1" and "child2" implement the GstChildProxy interface.

Details

GstChildProxy

typedef struct _GstChildProxy GstChildProxy;

Opaque GstChildProxy data structure.

struct GstChildProxyInterface

struct GstChildProxyInterface {
  GTypeInterface parent;

  /* methods */
  GstObject *(*get_child_by_index) (GstChildProxy * parent, guint index);
  guint (*get_children_count) (GstChildProxy * parent);
};

GstChildProxy interface.

GTypeInterface parent;

 parent interface type.

get_child_by_index ()

 virtual method to fetch the child

get_children_count ()

 virtual method to get the children count

gst_child_proxy_get_children_count ()

guint               gst_child_proxy_get_children_count  (GstChildProxy *parent);

Gets the number of child objects this parent contains.

parent :

 the parent object

Returns :

 the number of child objects MT safe.

gst_child_proxy_get_child_by_name ()

GstObject *         gst_child_proxy_get_child_by_name   (GstChildProxy *parent,
                                                         const gchar *name);

Looks up a child element by the given name.

Implementors can use GstObject together with gst_object_get_name()

parent :

 the parent object to get the child from

name :

 the childs name

Returns :

 the child object or NULL if not found. Unref after usage. MT safe. [transfer full]

gst_child_proxy_get_child_by_index ()

GstObject *         gst_child_proxy_get_child_by_index  (GstChildProxy *parent,
                                                         guint index);

Fetches a child by its number.

parent :

 the parent object to get the child from

index :

 the childs position in the child list

Returns :

 the child object or NULL if not found (index too high). Unref after usage. MT safe. [transfer full]

gst_child_proxy_lookup ()

gboolean            gst_child_proxy_lookup              (GstObject *object,
                                                         const gchar *name,
                                                         GstObject **target,
                                                         GParamSpec **pspec);

Looks up which object and GParamSpec would be effected by the given name.

object :

 object to lookup the property in

name :

 name of the property to look up

target :

 pointer to a GstObject that takes the real object to set property on. [out][allow-none][transfer full]

pspec :

 pointer to take the GParamSpec describing the property. [out][allow-none][transfer full]

Returns :

 TRUE if target and pspec could be found. FALSE otherwise. In that case the values for pspec and target are not modified. Unref target after usage. MT safe.

gst_child_proxy_get_property ()

void                gst_child_proxy_get_property        (GstObject *object,
                                                         const gchar *name,
                                                         GValue *value);

Gets a single property using the GstChildProxy mechanism. You are responsible for for freeing it by calling g_value_unset()

object :

 object to query

name :

 name of the property

value :

 a GValue that should take the result. [out caller-allocates]

gst_child_proxy_get_valist ()

void                gst_child_proxy_get_valist          (GstObject *object,
                                                         const gchar *first_property_name,
                                                         va_list var_args);

Gets properties of the parent object and its children.

object :

 the object to query

first_property_name :

 name of the first property to get

var_args :

 return location for the first property, followed optionally by more name/return location pairs, followed by NULL

gst_child_proxy_get ()

void                gst_child_proxy_get                 (GstObject *object,
                                                         const gchar *first_property_name,
                                                         ...);

Gets properties of the parent object and its children.

object :

 the parent object

first_property_name :

 name of the first property to get

... :

 return location for the first property, followed optionally by more name/return location pairs, followed by NULL

gst_child_proxy_set_property ()

void                gst_child_proxy_set_property        (GstObject *object,
                                                         const gchar *name,
                                                         const GValue *value);

Sets a single property using the GstChildProxy mechanism.

object :

 the parent object

name :

 name of the property to set

value :

 new GValue for the property

gst_child_proxy_set_valist ()

void                gst_child_proxy_set_valist          (GstObject *object,
                                                         const gchar *first_property_name,
                                                         va_list var_args);

Sets properties of the parent object and its children.

object :

 the parent object

first_property_name :

 name of the first property to set

var_args :

 value for the first property, followed optionally by more name/value pairs, followed by NULL

gst_child_proxy_set ()

void                gst_child_proxy_set                 (GstObject *object,
                                                         const gchar *first_property_name,
                                                         ...);

Sets properties of the parent object and its children.

object :

 the parent object

first_property_name :

 name of the first property to set

... :

 value for the first property, followed optionally by more name/value pairs, followed by NULL

gst_child_proxy_child_added ()

void                gst_child_proxy_child_added         (GstObject *object,
                                                         GstObject *child);

Emits the "child-added" signal.

object :

 the parent object

child :

 the newly added child

gst_child_proxy_child_removed ()

void                gst_child_proxy_child_removed       (GstObject *object,
                                                         GstObject *child);

Emits the "child-removed" signal.

object :

 the parent object

child :

 the removed child

Signal Details

The "child-added" signal

void                user_function                      (GstChildProxy *child_proxy,
                                                        GObject       *object,
                                                        gpointer       user_data)        : Run First

Will be emitted after the object was added to the child_proxy.

child_proxy :

 the GstChildProxy

object :

 the GObject that was added

user_data :

 user data set when the signal handler was connected.

The "child-removed" signal

void                user_function                      (GstChildProxy *child_proxy,
                                                        GObject       *object,
                                                        gpointer       user_data)        : Run First

Will be emitted after the object was removed from the child_proxy.

child_proxy :

 the GstChildProxy

object :

 the GObject that was removed

user_data :

 user data set when the signal handler was connected.

See Also

GstBin
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