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Retired Document

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Glossary

blocked
The state where an application or thread is waiting for some event or action to occur. While blocked, that particular code path uses no processor time.

Classic Event Manager
The event handling interface used in Mac OS applications before the Carbon Event Manager. The Classic Event Manager often required a certain amount of polling of the event queue.

containment hierarchy
A hierarchy of event targets that determines which handler is to be called to process an event. Events are initially sent to the innermost (or lowest) relevant target in the hierarchy. If the handler associated with that event target does not handle the event (or if no handler exists), then the event is propagated to the next target in the hierarchy. If no handler in the hierarchy processes the event, the default handler is called.

event
A constant that notifies an application that some action is occurring, or has occurred.

event class
The general category an event belongs to, typically associated with an particular action or user-interface element. Example classes are window events and volume events. Compare event kind.

event kind
A specific type of event within an event class (for example, a mouse-down event). Compare event class.

event loop
In the Carbon Event Manager, an execution loop that obtains events from the Window Server and places them in an event queue. The event loop also fires timers.

event queue
A first-in-first-out stack where events pertaining to a thread are stored. Each preemptively-scheduled thread has its own event queue.

event target
An object to which an event is sent. An event target is typically a user-interface element, such as a control or a window.

event timer
A timer mechanism that fires once, or at periodic intervals, calling a callback procedure when doing so.

event type
The combination of event class and event kind that uniquely identifies an event to the Carbon Event Manager. See alsoevent class, event kind.

main event loop
The code loop where the application spends most of its time. The application is blocked while waiting for events. When an event occurs, the application processes it and then returns to the blocked state.

one-shot timer
A Carbon event timer that fires only once. See alsoevent timer.

peek
To examine an event in an event queue (obtaining its class, kind, parameters and so on) without removing it from the queue. Compare pull.

queue-synchronized state
The state of an input device accordiing to the events that have been dispatched from the event queue. This state may differ from the actual physical state of the input device.

standard event handler
The event handler that processes an event if the application did not install one for it.

standard toolbox dispatcher
In the Carbon Event Manager, the default event target for events when running under RunApplicationEventLoop. Events sent to the standard toolbox dispatcher are automatically routed to the appropriate event targets.

universal procedure pointer (UPP)
A generalized procedure pointer that allows code with different calling conventions to call each other. Some Carbon functions require you to pass UPPs for callbacks because the calling routine doesn't know in advance if your code is Mach-O based or CFM-based.

user focus
The window or text field control to which keyboard input is directed. The user can change the user focus by using the mouse or (sometimes) the Tab key.

user focus event target
Events sent to this target are automatically sent to the event target that has the current user focus. You can also install a handler on this target to intercept events before they get sent to the current user focus.

WaitNextEvent
The function that drove the event loop in older versions of the Mac OS. See alsoClassic Event Manager.

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