gstnavigation

gstnavigation — Interface for creating, sending and parsing navigation events.

Functions

Types and Values

Object Hierarchy

    GInterface
    ╰── GstNavigation

Includes

#include <gst/video/navigation.h>

Description

The Navigation interface is used for creating and injecting navigation related events such as mouse button presses, cursor motion and key presses. The associated library also provides methods for parsing received events, and for sending and receiving navigation related bus events. One main usecase is DVD menu navigation.

The main parts of the API are:

  • The GstNavigation interface, implemented by elements which provide an application with the ability to create and inject navigation events into the pipeline.

  • GstNavigation event handling API. GstNavigation events are created in response to calls on a GstNavigation interface implementation, and sent in the pipeline. Upstream elements can use the navigation event API functions to parse the contents of received messages.

  • GstNavigation message handling API. GstNavigation messages may be sent on the message bus to inform applications of navigation related changes in the pipeline, such as the mouse moving over a clickable region, or the set of available angles changing.

    The GstNavigation message functions provide functions for creating and parsing custom bus messages for signaling GstNavigation changes.

Functions

gst_navigation_send_event ()

void
gst_navigation_send_event (GstNavigation *navigation,
                           GstStructure *structure);

gst_navigation_send_key_event ()

void
gst_navigation_send_key_event (GstNavigation *navigation,
                               const char *event,
                               const char *key);

Parameters

navigation

The navigation interface instance

 

event

The type of the key event. Recognised values are "key-press" and "key-release"

 

key

Character representation of the key. This is typically as produced by XKeysymToString.

 

gst_navigation_send_mouse_event ()

void
gst_navigation_send_mouse_event (GstNavigation *navigation,
                                 const char *event,
                                 int button,
                                 double x,
                                 double y);

Sends a mouse event to the navigation interface. Mouse event coordinates are sent relative to the display space of the related output area. This is usually the size in pixels of the window associated with the element implementing the GstNavigation interface.

Parameters

navigation

The navigation interface instance

 

event

The type of mouse event, as a text string. Recognised values are "mouse-button-press", "mouse-button-release" and "mouse-move".

 

button

The button number of the button being pressed or released. Pass 0 for mouse-move events.

 

x

The x coordinate of the mouse event.

 

y

The y coordinate of the mouse event.

 

gst_navigation_send_command ()

void
gst_navigation_send_command (GstNavigation *navigation,
                             GstNavigationCommand command);

Sends the indicated command to the navigation interface.

Parameters

navigation

The navigation interface instance

 

command

The command to issue

 

gst_navigation_event_parse_command ()

gboolean
gst_navigation_event_parse_command (GstEvent *event,
                                    GstNavigationCommand *command);

Inspect a GstNavigation command event and retrieve the enum value of the associated command.

Parameters

event

A GstEvent to inspect.

 

command

Pointer to GstNavigationCommand to receive the type of the navigation event.

 

Returns

TRUE if the navigation command could be extracted, otherwise FALSE.


gst_navigation_event_parse_key_event ()

gboolean
gst_navigation_event_parse_key_event (GstEvent *event,
                                      const gchar **key);

Parameters

event

A GstEvent to inspect.

 

key

A pointer to a location to receive the string identifying the key press. The returned string is owned by the event, and valid only until the event is unreffed.

 

gst_navigation_event_parse_mouse_button_event ()

gboolean
gst_navigation_event_parse_mouse_button_event
                               (GstEvent *event,
                                gint *button,
                                gdouble *x,
                                gdouble *y);

Retrieve the details of either a GstNavigation mouse button press event or a mouse button release event. Determine which type the event is using gst_navigation_event_get_type() to retrieve the GstNavigationEventType.

Parameters

event

A GstEvent to inspect.

 

button

Pointer to a gint that will receive the button number associated with the event.

 

x

Pointer to a gdouble to receive the x coordinate of the mouse button event.

 

y

Pointer to a gdouble to receive the y coordinate of the mouse button event.

 

Returns

TRUE if the button number and both coordinates could be extracted, otherwise FALSE.


gst_navigation_event_parse_mouse_move_event ()

gboolean
gst_navigation_event_parse_mouse_move_event
                               (GstEvent *event,
                                gdouble *x,
                                gdouble *y);

Inspect a GstNavigation mouse movement event and extract the coordinates of the event.

Parameters

event

A GstEvent to inspect.

 

x

Pointer to a gdouble to receive the x coordinate of the mouse movement.

 

y

Pointer to a gdouble to receive the y coordinate of the mouse movement.

 

Returns

TRUE if both coordinates could be extracted, otherwise FALSE.


gst_navigation_message_get_type ()

GstNavigationMessageType
gst_navigation_message_get_type (GstMessage *message);

Check a bus message to see if it is a GstNavigation event, and return the GstNavigationMessageType identifying the type of the message if so.

Parameters

message

A GstMessage to inspect.

 

Returns

The type of the GstMessage, or GST_NAVIGATION_MESSAGE_INVALID if the message is not a GstNavigation notification.


gst_navigation_message_new_angles_changed ()

GstMessage *
gst_navigation_message_new_angles_changed
                               (GstObject *src,
                                guint cur_angle,
                                guint n_angles);

Creates a new GstNavigation message with type GST_NAVIGATION_MESSAGE_ANGLES_CHANGED for notifying an application that the current angle, or current number of angles available in a multiangle video has changed.

Parameters

src

A GstObject to set as source of the new message.

 

cur_angle

The currently selected angle.

 

n_angles

The number of viewing angles now available.

 

Returns

The new GstMessage.


gst_navigation_message_new_commands_changed ()

GstMessage *
gst_navigation_message_new_commands_changed
                               (GstObject *src);

Creates a new GstNavigation message with type GST_NAVIGATION_MESSAGE_COMMANDS_CHANGED

Parameters

src

A GstObject to set as source of the new message.

 

Returns

The new GstMessage.


gst_navigation_message_new_mouse_over ()

GstMessage *
gst_navigation_message_new_mouse_over (GstObject *src,
                                       gboolean active);

Creates a new GstNavigation message with type GST_NAVIGATION_MESSAGE_MOUSE_OVER.

Parameters

src

A GstObject to set as source of the new message.

 

active

TRUE if the mouse has entered a clickable area of the display. FALSE if it over a non-clickable area.

 

Returns

The new GstMessage.


gst_navigation_message_parse_mouse_over ()

gboolean
gst_navigation_message_parse_mouse_over
                               (GstMessage *message,
                                gboolean *active);

Parse a GstNavigation message of type GST_NAVIGATION_MESSAGE_MOUSE_OVER and extract the active/inactive flag. If the mouse over event is marked active, it indicates that the mouse is over a clickable area.

Parameters

message

A GstMessage to inspect.

 

active

A pointer to a gboolean to receive the active/inactive state, or NULL.

 

Returns

TRUE if the message could be successfully parsed. FALSE if not.


gst_navigation_message_parse_angles_changed ()

gboolean
gst_navigation_message_parse_angles_changed
                               (GstMessage *message,
                                guint *cur_angle,
                                guint *n_angles);

Parse a GstNavigation message of type GST_NAVIGATION_MESSAGE_ANGLES_CHANGED and extract the cur_angle and n_angles parameters.

Parameters

message

A GstMessage to inspect.

 

cur_angle

A pointer to a guint to receive the new current angle number, or NULL

 

n_angles

A pointer to a guint to receive the new angle count, or NULL.

 

Returns

TRUE if the message could be successfully parsed. FALSE if not.


gst_navigation_query_new_angles ()

GstQuery *
gst_navigation_query_new_angles (void);

Create a new GstNavigation angles query. When executed, it will query the pipeline for the set of currently available angles, which may be greater than one in a multiangle video.

Returns

The new query.


gst_navigation_query_get_type ()

GstNavigationQueryType
gst_navigation_query_get_type (GstQuery *query);

Inspect a GstQuery and return the GstNavigationQueryType associated with it if it is a GstNavigation query.

Parameters

query

The query to inspect

 

gst_navigation_query_new_commands ()

GstQuery *
gst_navigation_query_new_commands (void);

Create a new GstNavigation commands query. When executed, it will query the pipeline for the set of currently available commands.

Returns

The new query.


gst_navigation_query_parse_angles ()

gboolean
gst_navigation_query_parse_angles (GstQuery *query,
                                   guint *cur_angle,
                                   guint *n_angles);

Parse the current angle number in the GstNavigation angles query into the guint pointed to by the cur_angle variable, and the number of available angles into the guint pointed to by the n_angles variable.

Parameters

query

a GstQuery

 

cur_angle

Pointer to a guint into which to store the currently selected angle value from the query, or NULL

 

n_angles

Pointer to a guint into which to store the number of angles value from the query, or NULL

 

Returns

TRUE if the query could be successfully parsed. FALSE if not.


gst_navigation_query_parse_commands_length ()

gboolean
gst_navigation_query_parse_commands_length
                               (GstQuery *query,
                                guint *n_cmds);

Parse the number of commands in the GstNavigation commands query .

Parameters

query

a GstQuery

 

n_cmds

the number of commands in this query.

[out]

Returns

TRUE if the query could be successfully parsed. FALSE if not.


gst_navigation_query_parse_commands_nth ()

gboolean
gst_navigation_query_parse_commands_nth
                               (GstQuery *query,
                                guint nth,
                                GstNavigationCommand *cmd);

Parse the GstNavigation command query and retrieve the nth command from it into cmd . If the list contains less elements than nth , cmd will be set to GST_NAVIGATION_COMMAND_INVALID.

Parameters

query

a GstQuery

 

nth

the nth command to retrieve.

 

cmd

a pointer to store the nth command into.

[out]

Returns

TRUE if the query could be successfully parsed. FALSE if not.


gst_navigation_query_set_angles ()

void
gst_navigation_query_set_angles (GstQuery *query,
                                 guint cur_angle,
                                 guint n_angles);

Set the GstNavigation angles query result field in query .

Parameters

query

a GstQuery

 

cur_angle

the current viewing angle to set.

 

n_angles

the number of viewing angles to set.

 

gst_navigation_query_set_commands ()

void
gst_navigation_query_set_commands (GstQuery *query,
                                   gint n_cmds,
                                   ...);

Set the GstNavigation command query result fields in query . The number of commands passed must be equal to n_commands .

Parameters

query

a GstQuery

 

n_cmds

the number of commands to set.

 

...

A list of GstNavigationCommand values, n_cmds entries long.

 

gst_navigation_query_set_commandsv ()

void
gst_navigation_query_set_commandsv (GstQuery *query,
                                    gint n_cmds,
                                    GstNavigationCommand *cmds);

Set the GstNavigation command query result fields in query . The number of commands passed must be equal to n_commands .

Parameters

query

a GstQuery

 

n_cmds

the number of commands to set.

 

cmds

An array containing n_cmds GstNavigationCommand values.

 

Types and Values

GstNavigation

typedef struct _GstNavigation GstNavigation;

struct GstNavigationInterface

struct GstNavigationInterface {
  GTypeInterface iface;

  /* virtual functions */
  void (*send_event) (GstNavigation *navigation, GstStructure *structure);
};

Navigation interface.

Members

GTypeInterface iface;

the parent interface

 

send_event ()

sending a navigation event

 

enum GstNavigationCommand

A set of commands that may be issued to an element providing the GstNavigation interface. The available commands can be queried via the gst_navigation_query_new_commands() query.

For convenience in handling DVD navigation, the MENU commands are aliased as: GST_NAVIGATION_COMMAND_DVD_MENU = GST_NAVIGATION_COMMAND_MENU1 GST_NAVIGATION_COMMAND_DVD_TITLE_MENU = GST_NAVIGATION_COMMAND_MENU2 GST_NAVIGATION_COMMAND_DVD_ROOT_MENU = GST_NAVIGATION_COMMAND_MENU3 GST_NAVIGATION_COMMAND_DVD_SUBPICTURE_MENU = GST_NAVIGATION_COMMAND_MENU4 GST_NAVIGATION_COMMAND_DVD_AUDIO_MENU = GST_NAVIGATION_COMMAND_MENU5 GST_NAVIGATION_COMMAND_DVD_ANGLE_MENU = GST_NAVIGATION_COMMAND_MENU6 GST_NAVIGATION_COMMAND_DVD_CHAPTER_MENU = GST_NAVIGATION_COMMAND_MENU7

Members

GST_NAVIGATION_COMMAND_INVALID

An invalid command entry

 

GST_NAVIGATION_COMMAND_MENU1

Execute navigation menu command 1. For DVD, this enters the DVD root menu, or exits back to the title from the menu.

 

GST_NAVIGATION_COMMAND_MENU2

Execute navigation menu command 2. For DVD, this jumps to the DVD title menu.

 

GST_NAVIGATION_COMMAND_MENU3

Execute navigation menu command 3. For DVD, this jumps into the DVD root menu.

 

GST_NAVIGATION_COMMAND_MENU4

Execute navigation menu command 4. For DVD, this jumps to the Subpicture menu.

 

GST_NAVIGATION_COMMAND_MENU5

Execute navigation menu command 5. For DVD, the jumps to the audio menu.

 

GST_NAVIGATION_COMMAND_MENU6

Execute navigation menu command 6. For DVD, this jumps to the angles menu.

 

GST_NAVIGATION_COMMAND_MENU7

Execute navigation menu command 7. For DVD, this jumps to the chapter menu.

 

GST_NAVIGATION_COMMAND_LEFT

Select the next button to the left in a menu, if such a button exists.

 

GST_NAVIGATION_COMMAND_RIGHT

Select the next button to the right in a menu, if such a button exists.

 

GST_NAVIGATION_COMMAND_UP

Select the button above the current one in a menu, if such a button exists.

 

GST_NAVIGATION_COMMAND_DOWN

Select the button below the current one in a menu, if such a button exists.

 

GST_NAVIGATION_COMMAND_ACTIVATE

Activate (click) the currently selected button in a menu, if such a button exists.

 

GST_NAVIGATION_COMMAND_PREV_ANGLE

Switch to the previous angle in a multiangle feature.

 

GST_NAVIGATION_COMMAND_NEXT_ANGLE

Switch to the next angle in a multiangle feature.

 

enum GstNavigationEventType

Enum values for the various events that an element implementing the GstNavigation interface might send up the pipeline.

Members

GST_NAVIGATION_EVENT_INVALID

Returned from gst_navigation_event_get_type() when the passed event is not a navigation event.

 

GST_NAVIGATION_EVENT_KEY_PRESS

A key press event. Use gst_navigation_event_parse_key_event() to extract the details from the event.

 

GST_NAVIGATION_EVENT_KEY_RELEASE

A key release event. Use gst_navigation_event_parse_key_event() to extract the details from the event.

 

GST_NAVIGATION_EVENT_MOUSE_BUTTON_PRESS

A mouse button press event. Use gst_navigation_event_parse_mouse_button_event() to extract the details from the event.

 

GST_NAVIGATION_EVENT_MOUSE_BUTTON_RELEASE

A mouse button release event. Use gst_navigation_event_parse_mouse_button_event() to extract the details from the event.

 

GST_NAVIGATION_EVENT_MOUSE_MOVE

A mouse movement event. Use gst_navigation_event_parse_mouse_move_event() to extract the details from the event.

 

GST_NAVIGATION_EVENT_COMMAND

A navigation command event. Use gst_navigation_event_parse_command() to extract the details from the event.

 

enum GstNavigationMessageType

A set of notifications that may be received on the bus when navigation related status changes.

Members

GST_NAVIGATION_MESSAGE_INVALID

Returned from gst_navigation_message_get_type() when the passed message is not a navigation message.

 

GST_NAVIGATION_MESSAGE_MOUSE_OVER

Sent when the mouse moves over or leaves a clickable region of the output, such as a DVD menu button.

 

GST_NAVIGATION_MESSAGE_COMMANDS_CHANGED

Sent when the set of available commands changes and should re-queried by interested applications.

 

GST_NAVIGATION_MESSAGE_ANGLES_CHANGED

Sent when display angles in a multi-angle feature (such as a multiangle DVD) change - either angles have appeared or disappeared.

 

enum GstNavigationQueryType

Tyoes of navigation interface queries.

Members

GST_NAVIGATION_QUERY_INVALID

invalid query

 

GST_NAVIGATION_QUERY_COMMANDS

command query

 

GST_NAVIGATION_QUERY_ANGLES

viewing angle query

 

GST_NAVIGATION_COMMAND_DVD_ANGLE_MENU

#define GST_NAVIGATION_COMMAND_DVD_ANGLE_MENU      GST_NAVIGATION_COMMAND_MENU6

GST_NAVIGATION_COMMAND_DVD_AUDIO_MENU

#define GST_NAVIGATION_COMMAND_DVD_AUDIO_MENU      GST_NAVIGATION_COMMAND_MENU5

GST_NAVIGATION_COMMAND_DVD_CHAPTER_MENU

#define GST_NAVIGATION_COMMAND_DVD_CHAPTER_MENU    GST_NAVIGATION_COMMAND_MENU7

GST_NAVIGATION_COMMAND_DVD_MENU

#define GST_NAVIGATION_COMMAND_DVD_MENU            GST_NAVIGATION_COMMAND_MENU1

GST_NAVIGATION_COMMAND_DVD_ROOT_MENU

#define GST_NAVIGATION_COMMAND_DVD_ROOT_MENU       GST_NAVIGATION_COMMAND_MENU3

GST_NAVIGATION_COMMAND_DVD_SUBPICTURE_MENU

#define GST_NAVIGATION_COMMAND_DVD_SUBPICTURE_MENU GST_NAVIGATION_COMMAND_MENU4

GST_NAVIGATION_COMMAND_DVD_TITLE_MENU

#define GST_NAVIGATION_COMMAND_DVD_TITLE_MENU      GST_NAVIGATION_COMMAND_MENU2