Starboard Module Reference: event.h

Defines the event system that wraps the Starboard main loop and entry point.

The Starboard Application life cycle

          |                      _________________________
        Start                   |                         |
          |                     |                       Resume
          V                     V                         |
     [ STARTED ] --Pause--> [ PAUSED ] --Suspend--> [ SUSPENDED ]
          ^                     |                         |
          |                  Unpause                     Stop
          |_____________________|                         |
                                                     [ STOPPED ]

The first event that a Starboard application receives is Start (kSbEventTypeStart). This puts the application in the |STARTED| state. The application is in the foreground and can expect to do all of the normal things it might want to do. Once in the |STARTED| state, it may receive a |Pause| event, putting the application into the |PAUSED| state.
In the |PAUSED| state, the application is still visible, but has lost focus, or it is partially obscured by a modal dialog, or it is on its way to being shut down. The application should pause activity in this state. In this state, it can receive |Unpause| to be brought back to the foreground state (|STARTED|), or |Suspend| to be pushed further in the background to the |SUSPENDED| state.
In the |SUSPENDED| state, the application is generally not visible. It should immediately release all graphics and video resources, and shut down all background activity (timers, rendering, etc). Additionally, the application should flush storage to ensure that if the application is killed, the storage will be up-to-date. The application may be killed at this point, but will ideally receive a |Stop| event for a more graceful shutdown.
Note that the application is always expected to transition through |PAUSED| to |SUSPENDED| before receiving |Stop| or being killed.



An enumeration of all possible event types dispatched directly by the system. Each event is accompanied by a void* data argument, and each event must define the type of the value pointed to by that data argument, if any.


  • kSbEventTypeStart - The first event that an application receives on startup. Applications should perform initialization and prepare to react to subsequent events.Applications that wish to run and then exit must call SbSystemRequestStop()to terminate. This event will only be sent once for a given process launch.SbEventStartData is passed as the data argument.
  • kSbEventTypePause - A dialog will be raised or the application will otherwise be put into abackground-but-visible or partially-obscured state (PAUSED). Graphics andvideo resources will still be available, but the application should pauseforeground activity like animations and video playback. Can only bereceived after a Start event. The only events that should be dispatchedafter a Pause event are Unpause or Suspend. No data argument.
  • kSbEventTypeUnpause - The application is returning to the foreground (STARTED) after having beenput in the PAUSED (e.g. partially-obscured) state. The application shouldunpause foreground activity like animations and video playback. Can only bereceived after a Pause or Resume event. No data argument.
  • kSbEventTypeSuspend - The operating system will put the application into a Suspended state afterthis event is handled. The application is expected to stop periodicbackground work, release ALL graphics and video resources, and flush anypending SbStorage writes. Some platforms will terminate the application ifwork is done or resources are retained after suspension. Can only bereceived after a Pause event. The only events that should be dispatchedafter a Suspend event are Resume or Stop. On some platforms, the processmay also be killed after Suspend without a Stop event. No data argument.
  • kSbEventTypeResume - The operating system has restored the application to the PAUSED state fromthe SUSPENDED state. This is the first event the application will receivecoming out of SUSPENDED, and it will only be received after a Suspendevent. The application will now be in the PAUSED state. No data argument.
  • kSbEventTypeStop - The operating system will shut the application down entirely after thisevent is handled. Can only be recieved after a Suspend event, in theSUSPENDED state. No data argument.
  • kSbEventTypeInput - A user input event, including keyboard, mouse, gesture, or something else.SbInputData (from input.h) is passed as the data argument.
  • kSbEventTypeUser - A user change event, which means a new user signed-in or signed-out, or thecurrent user changed. No data argument, call SbUserGetSignedIn() andSbUserGetCurrent() to get the latest changes.
  • kSbEventTypeLink - A navigational link has come from the system, and the application shouldconsider handling it by navigating to the corresponding applicationlocation. The data argument is an application-specific, null-terminatedstring.
  • kSbEventTypeVerticalSync - The beginning of a vertical sync has been detected. This event is verytiming-sensitive, so as little work as possible should be done on the mainthread if the application wants to receive this event in a timely manner.No data argument.
  • kSbEventTypeNetworkDisconnect - The platform has detected a network disconnection. The platform should makea best effort to send an event of this type when the network disconnects,but there are likely to be cases where the platform cannot detect thedisconnection (e.g. if the connection is via a powered hub which becomesdisconnected), so the current network state cannot always be inferred fromthe sequence of Connect/Disconnect events.
  • kSbEventTypeNetworkConnect - The platform has detected a network connection. This event may be sent atapplication start-up, and should always be sent if the network reconnectssince a disconnection event was sent.
  • kSbEventTypeScheduled - An event type reserved for scheduled callbacks. It will only be sent inresponse to an application call to SbEventSchedule(), and it will call thecallback directly, so SbEventHandle should never receive this eventdirectly. The data type is an internally-defined structure.



Structure representing a Starboard event and its data.




Event data for kSbEventTypeStart events.


The command-line argument count (argc).
char* link
The startup link, if any.




Cancels the specified event_id. Note that this function is a no-op if the event already fired. This function can be safely called from any thread, but the only way to guarantee that the event does not run anyway is to call it from the main Starboard event loop thread.


SB_EXPORT void SbEventCancel(SbEventId event_id);





The entry point that Starboard applications MUST implement. Any memory pointed at by event or the data field inside event is owned by the system, and that memory is reclaimed after this function returns, so the implementation must copy this data to extend its life. This behavior should also be assumed of all fields within the data object, unless otherwise explicitly specified.
This function is only called from the main Starboard thread. There is no specification about what other work might happen on this thread, so the application should generally do as little work as possible on this thread, and just dispatch it over to another thread.


SB_IMPORT void SbEventHandle(const SbEvent* event);


const SbEvent*



Returns whether the given event handle is valid.


static SB_C_FORCE_INLINE bool SbEventIsIdValid(SbEventId handle) {
  return handle != kSbEventIdInvalid;





Schedules an event callback into the main Starboard event loop. This function may be called from any thread, but callback is always called from the main Starboard thread, queued with other pending events.


SB_EXPORT SbEventId SbEventSchedule(SbEventCallback callback,
                                    void* context,
                                    SbTime delay);


The callback function to be called.
The context that is passed to the callback function.
The minimum number of microseconds to wait before calling the callback function. Set delay to 0 to call the callback as soon as possible.