About The Notification Manager and System 7.0
users of significant occurrences in applications that are running in the
background or in software that is largely invisible to the user. This software
includes device drivers, vertical blanking (VBL) tasks, Time Manager tasks,
completion routines, and desk accessories that operate behind the scenes. It
also includes code that executes during the system startup sequence, such as
code contained in 'INIT' resources.
later. You can use the Gestalt function to determine whether the Notification
on using Gestalt.
The information in this section supersedes the information that was
previously published in Appendix D of the Programmer's Guide to MultiFinder.
You need to read this section if your application, desk accessory, or device
driver might need to notify the user of some occurrence while it is running in
the background or is otherwise invisible to the user. You also need to read this
section if you want to write 'INIT' resources that might need to inform the user
of important occurrences during their execution at system startup time.
It allows software running in the background (or otherwise unseen by the
user) to communicate information to the user. For example, applications that
manage lengthy background tasks (such as printing many documents or
transferring large amounts of data to other machines) might need to inform
the user that the operation is complete. These applications cannot use the
standard methods of communicating with the user, such as alert or dialog
boxes, because such windows might easily be obscured by the windows of other
applications. Moreover, even if those windows are visible, the background
application cannot be certain that the user is aware of the change. So some
more reliable method must be used to manage the communication between a
background application and the user, who might be awaiting the completion of
the background task while running other applications in the foreground.
In the same way, relatively invisible operations such as Time Manager tasks,
VBL tasks, or device drivers might need to inform the user that some
previously started routine is complete or perhaps that some error has
rendered further execution undesirable or im possible.
In all these cases, the communication generally needs to occur in one direction
only, from the background application (or task, or driver) to the user. The
Notification Manager, included in system software versions 6.0 and later,
allows you to post to the user a notification, which is an audible or visible
indication that your application (or other piece of software) requires the
user's attention. You post a notification by issuing a notification request to the
Notification Manager, which places your request into a queue. When your
notification to the user.
You can request three types of notification:
• Polite notification. A small icon appears to flash by periodically
alternating with the Apple menu icon (which is the Apple symbol) or
the Application menu icon in the menu bar.
sound or a sound contained in an 'snd ' resource.
• Alert notification. An alert box containing a short message appears
on the screen. The user must dismiss the alert box (by clicking the OK
button) before foreground processing can continue.
These types of notification are not mutually exclusive; for example, an
application can request both audible and alert notifications. Moreover, if the
requesting software is listed in the Application menu (and hence represents a
process that is loaded into memory), you can instruct the Notification
Manager to place a diamond-shaped mark next to the name of the requesting
process. The mark is usually intended to prompt the user to switch the marked
application into the foreground. Finally, you can request that the
Notification Manager execute a notification response procedure, which is
a procedure that is executed as the final step in a notification.
In short, a notification consists of one or more of five possible actions. If you
request more than one action, they occur in the following order:
1. A diamond-shaped mark appears next to the name of your application
in the Application menu, as illustrated in the Figure below. Note that the
diamond is present only when your application is in the background (because
the diamond is replaced by a checkmark if your application is the active
application). In the Figure below, the Other App application is the active
application.
2. A small icon alternates with the Apple menu icon or the Application
menu icon in the menu bar. Typically, the small icon is your application's
small icon. Note that several applications might post notifications, so there
might be a series of small icons alternating in the menu bar. The location of
each flashing icon follows that of the posting application's mark (if any). If
your application is marked with a diamond (or a checkmark) in the Application
menu, the icon flashes above the Application menu; otherwise, the icon flashes
above the Apple menu.
user's system alert sound.
A notification in the Application menu
4. An alert box appears, and the user dismisses it. Your application
specifies the text in the alert box.
5. A response procedure executes. You can use the response procedure to
remove the notification request from the queue or perform other processing.
The mark in the Application menu and the alternating small icon remain until
the requesting application removes the notification request from the queue.
However, the sound and the alert box are presented only once, if at all.
Any applications, desk accessories, tasks, routines, or drivers can use the
Notification Manager, whether they are running in the background or not.
It is especially useful for background applications, such as the PrintMonitor
application. (The system alarm, which is called by the Alarm Clock desk
effects (such as the alternating small icon) that are otherwise more difficult
even to applications that might be executing in a Finder-only environment
under system software version 6.0.
interface for notifying the user of significant events. It is suggested that your
application adopt the following three-level notification strategy for
communicating with the user:
1. Display a diamond next to the name of the application in the
Application menu.
2. Insert a small icon into the list of icons that alternate with the Apple
menu icon or the Application menu icon in the menu bar, and display a diamond
next to the name of your application in the Application menu.
3. Display a diamond, insert a small icon, and put up an alert box to
notify the user that something needs to be done.
Ideally, the user should be allowed to set the desired level of notification. The
suggested default level of notification is level 2. In levels 2 and 3, you might
also play a sound, but the user should have the ability to turn the sound off. In
addition, a user should have the ability to turn off background notification
altogether, except in cases where damage might occur or data would be lost.
Note: This suggested notification strategy may not be appropriate
for your application. Notifications posted by system software do not
follow these guidelines.
Each application, desk accessory, and device driver can issue any number of
notification requests. Each requested notification is presented separately to the
user. For this reason, you should try to avoid posting multiple notification
requests for the same occurrence. Depending on the method of notification you
specify, multiple requests might result in an annoying number of notification
sounds or a large number of alert boxes that the user must dismiss before
continuing.
path from an application to the user. There is no provision for carrying
information back from the user to the requesting application, although it is
possible for the requesting application to determine if the notification was
received. If you require this secondary communications link, do not use the
Notification Manager. Instead, you should wait until the user switches
your application into the foreground and then use standard means (for
example, a dialog box) to obtain the required information.