Derived from: none
Declared in: <app/Roster.h>
The BRoster object represents a service that keeps a roster of all applications currently running. It can provide information about any of those applications, activate one of them, add another application to the roster by launching it, or get information about an application to help you decide whether to launch it.
There's just one roster and it's shared by all applications. When an application starts up, a BRoster object is constructed and assigned to a global variable, be_roster. You always access the roster through this variable; you never have to instantiate a BRoster in application code.
The BRoster identifies applications in three ways:
If an application is launched more than once, the roster will include one entry for each instance of the application that's running. These instances will have the same signature, but different team identifiers.
BRoster(void)
Sets up the object's connection to the roster service.
When an application constructs its BApplication object, the system constructs a BRoster object and assigns it to the be_roster global variable. A BRoster is therefore readily available from the time the application is initialized until the time it quits; you don't have to construct one. The constructor is public only to give programs that don't have BApplication objects access to the roster.
~BRoster(void)
Does nothing.
status_t ActivateApp(team_id team) const
Activates the team application < by bringing one of its windows to the front and making it the active window >. This function works only if the target application has a window on-screen. The newly activated application is notified with a B_APP_ACTIVATED message.
See also: BApplication::AppActivated()
status_t Broadcast(BMessage *message) const
Sends the message to every running application, except to those applications (B_ARGV_ONLY) that don't accept messages. The message is sent asynchronously with a timeout of 0. As is the case for other message-sending functions, the caller retains ownership of the message.
This function returns immediately after setting up the broadcast operation. It doesn't wait for the messages to be sent and doesn't report any errors encountered when they are. It returns an error only if it can't start the broadcast operation. If successful in getting the operation started, it returns B_OK.
See also: BMessenger::SendMessage()
status_t FindApp(const char *type, entry_ref *app) const
status_t FindApp(entry_ref *file, entry_ref *app) const
Finds the application associated with the MIME data type or with the specified file, and modifies the app entry_ref structure so that it refers to the executable file for that application. If the type is an application signature, this function finds the application that has that signature. Otherwise, it finds the preferred application for the type. If the file is an application executable, FindApp() merely copies the file reference to the app argument. Otherwise, it finds the preferred application for the file type.
In other words, this function goes about finding an application in the same way that Launch() finds the application it will launch.
If it can translate the type or file into a reference to an application executable, FindApp() returns B_OK. If not, it returns an error code, typically one describing a file system error.
See also: Launch()
status_t GetAppInfo(cons char *signature, app_info *appInfo) const
status_t GetAppInfo(entry_ref *executable, app_info *appInfo) const
status_t GetRunningAppInfo(team_id team, app_info *appInfo) const
status_t GetActiveAppInfo(app_info *appInfo) const
These functions provide information about the application identified by its signature, by a reference to its executable file, by its team, or simply by its status as the current active application. They place the information in the structure referred to by appInfo.
GetRunningAppInfo() reports on a particular instance of a running application, the one that was assigned the team identifier at launch. GetActiveAppInfo() similarly reports on a running application, the one that happens to be the current active application.
If it can, GetAppInfo() also tries to get information about an application that's running. If a running application has the signature identifier or was launched from the executable file, GetAppInfo() queries it for the information. If more than one instance of the signature application is running, or if more than one instance was launched from the same executable file, it arbitrarily picks one of the instances to report on.
Even if the application isn't running--if none of the applications currently in the roster are identified by signature or were launched from the executable file--GetAppInfo() can still provide some information about it, perhaps enough information for you to call Launch() to get it started.
If they're able to fill in the app_info structure with meaningful values, these functions return B_OK. However, GetActiveAppInfo() returns B_ERROR if there's no active application. GetRunningAppInfo() returns B_BAD_TEAM_ID if team isn't, on the face of it, a valid team identifier for a running application. GetAppInfo() returns B_BAD_VALUE if the signature doesn't correspond to an application on-disk, and simply B_ERROR if the executable doesn't refer to a valid record in the database or doesn't refer to a record for an executable file.
The app_info structure contains the following fields:
| thread_id thread | The identifier for the application's main thread of execution, or -1 if the application isn't running. (The main thread is the thread in which the application is launched and in which its main() function runs.) |
| team_id team | The identifier for the application's team, or -1 if the application isn't running. (This will be the same as the team passed to GetRunningAppInfo().) |
| port_id port | The port where the application's main thread receives messages, or -1 if the application isn't running. |
| uint32 flags | A mask that contains information about the behavior of the application. |
| entry_ref ref | A reference to the file that was, or could be, executed to run the application. (This will be the same as the executable passed to GetAppInfo().) |
| char signature[] | The signature of the application. (This will be the same as the signature passed to GetAppInfo().) |
The flags mask can be tested (with the bitwise & operator) against these two constants:
| B_BACKGROUND_APP | The application won't appear in the track bar (because it doesn't have a user interface or because it can't become the active application). |
| B_ARGV_ONLY | The application can't receive messages. Information can be passed to it at launch only, in an array of argument strings (as on the command line). |
The flags mask also contains a value that explains the application's launch behavior. This value must be filtered out of flags by combining flags with the B_LAUNCH_MASK constant. For example:
unit32 behavior = theInfo.flags & B_LAUNCH_MASK;
The result will match one of these three constants:
| B_EXCLUSIVE_LAUNCH | The application can be launched only if an application with the same signature isn't already running. |
| B_SINGLE_LAUNCH | The application can be launched only once from the same executable file. However, an application with the same signature might be launched from a different executable. For example, if the user copies an executable file to another directory, a separate instance of the application can be launched from each copy. |
| B_MULTIPLE_LAUNCH | There are no restrictions. The application can be launched any number of times from the same executable file. |
These flags affect BRoster's Launch() function. Launch() can always start up a B_MULTIPLE_LAUNCH application. However, it can't launch a B_SINGLE_LAUNCH application if a running application was already launched from the same executable file. It can't launch a B_EXCLUSIVE_LAUNCH application if an application with the same signature is already running.
See also: Launch(), BApplication::GetAppInfo()
void GetAppList(BList *teams) const
void GetAppList(const char *signature, BList *teams) const
Fills in the teams BList with team identifiers for applications in the roster. Each item in the list will be of type team_id. It must be cast to that type when retrieving it from the list, as follows:
BList *teams = new BList; be_roster->GetAppList(teams); team_id who = (team_id)teams->ItemAt(someIndex);
The list will contain one item for each instance of an application that's running. For example, if the same application has been launched three times, the list will include the team_ids for all three running instances of that application.
If a signature is passed, the list identifies only applications running under that signature. If a signature isn't specified, the list identifies all running applications.
See also: TeamFor(), the BMessenger constructor
status_t Launch(const char *type, BMessage *message = NULL,
team_id *team = NULL) const
status_t Launch(const char *type, BList *messages,
team_id *team = NULL) const
status_t Launch(const char *type, int argc, char **argv,
team_id *team = NULL) const
status_t Launch(entry_ref *file, BMessage *message = NULL,
team_id *team = NULL) const
status_t Launch(entry_ref *file, BList *messages,
team_id *team = NULL) const
status_t Launch(entry_ref *file, int argc, char **argv,
team_id *team = NULL) const
Launches the application associated with a MIME type or with a particular file. If the MIME type is an application signature, this function launches the application with that signature. Otherwise, it launches the preferred application for the type. If the file is an application executable, it launches that application. Otherwise, it launches the preferred application for the file type and passes the file reference to the application in a B_REFS_RECEIVED message. In other words, Launch() finds the application to launch just as FindApp() finds the application for a particular type or file.
If a message is specified, it will be sent to the application on-launch where it will be received and responded to before the application is notified that it's ready to run. Similarly, if a list of messages is specified, each one will be delivered on-launch. The caller retains ownership of the BMessage objects (and the container BList); they won't be deleted for you.
Sending an on-launch message is appropriate if it helps the launched application configure itself before it starts getting other messages. To launch an application and send it an ordinary message, call Launch() to get it running, then set up a BMessenger object for the application and call BMessenger's SendMessage() function.
If the target application is already running, Launch() won't launch it again, unless it permits multiple instances to run concurrently (it doesn't wait for the messages to be sent or report errors encountered when they are). It fails for B_SINGLE_LAUNCH and B_EXCLUSIVE_LAUNCH applications that have already been launched. Nevertheless, it assumes that you want the messages to get to the application and so delivers them to the currently running instance.
Instead of messages, you can launch an application with an array of argument strings that will be passed to its main() function. argv contains the array and argc counts the number of strings. If the application accepts messages, this information will also be packaged in a B_ARGV_RECEIVED message that the application will receive on-launch.
If successful, Launch() places the identifier for the newly launched application in the variable referred to by team and returns B_OK. If unsuccessful, it sets the team variable to -1 and returns an error code, typically one of the following:
| B_BAD_VALUE | The type or file is not valid, or an attempt is being made to send an on-launch message to an application that doesn't accept messages (that is, to a B_ARGV_ONLY application). |
| B_ALREADY_RUNNING | The application is already running and can't be launched again (it's a B_SINGLE_LAUNCH or B_EXCLUSIVE_LAUNCH application). |
| B_LAUNCH_FAILED | The attempt to launch the application failed for some other reason, such as insufficient memory. |
| A file system error | The file or type can't be matched to an application. |
See also: the BMessenger class, GetAppInfo(), FindApp()
team_id TeamFor(const char *signature) const
team_id TeamFor(entry_ref *executable) const
bool IsRunning(const char *signature) const
bool IsRunning(entry_ref *executable) const
Both these functions query whether the application identified by its signature or by a reference to its executable file is running. TeamFor() returns its team identifier if it is, and B_ERROR if it's not. IsRunning() returns true if it is, and false if it's not.
If the application is running, you probably will want its team identifier (to set up a BMessenger, for example). Therefore, it's most economical to simply call TeamFor() and forego IsRunning().
If more than one instance of the signature application is running, or if more than one instance was launched from the same executable file, TeamFor() arbitrarily picks one of the instances and returns its team_id.
See also: GetAppList()
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Last modified June 30, 1997.