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XtAppNextEvent(3Xt)
X11R6
NAME
  XtAppNextEvent, XtAppPending, XtAppPeekEvent, XtAppProcessEvent,
  XtDispatchEvent, XtAppMainLoop - query and process events and input

SYNOPSIS
  void XtAppNextEvent(app_context, event_return)
	  XtAppContext app_context;
	  XEvent *event_return;

  Boolean XtAppPeekEvent(app_context, event_return)
	  XtAppContext app_context;
	  XEvent *event_return;

  XtInputMask XtAppPending(app_context)
	  XtAppContext app_context;

  void XtAppProcessEvent(app_context, mask)
	  XtAppContext app_context;
	  XtInputMask mask;

  Boolean XtDispatchEvent(event)
	  XEvent *event;

  void XtAppMainLoop(app_context)
	  XtAppContext app_context;

ARGUMENTS
  app_context
      Specifies the application context that identifies the application.

  event
      Specifies a pointer to the event structure that is to be dispatched to
      the appropriate event handler.

  event_return
      Returns the event information to the specified event structure.

  mask
      Specifies what types of events to process. The mask is the bitwise
      inclusive OR of any combination of XtIMXEvent, XtIMTimer,
      XtIMAlternateInput, and XtIMSignal. As a convenience, the X Toolkit
      defines the symbolic name XtIMAll to be the bitwise inclusive OR of all
      event types.

DESCRIPTION
  If the X event queue is empty, XtAppNextEvent flushes the X output buffers
  of each Display in the application context and waits for an event while
  looking at the other input sources, timeout values, and signal handlers and
  calling any callback procedures triggered by them.  This wait time can be
  used for background processing (see Section 7.8).

  If there is an event in the queue, XtAppPeekEvent fills in the event and
  returns a nonzero value. If no X input is on the queue, XtAppPeekEvent
  flushes the output buffer and blocks until input is available (possibly
  calling some timeout callbacks in the process). If the input is an event,
  XtAppPeekEvent fills in the event and returns a nonzero value. Otherwise,
  the input is for an alternate input source, and XtAppPeekEvent returns
  zero.

  The XtAppPending function returns a nonzero value if there are events
  pending from the X server, timer pending, or other input sources pending.
  The value returned is a bit mask that is the OR of XtIMXEvent, XtIMTimer,
  XtIMAlternateInput, and XtIMSignal (see XtAppProcessEvent). If there are no
  events pending, XtAppPending flushes the output buffer and returns zero.

  The XtAppProcessEvent function processes one timer, alternate input, signal
  source, or X event.  If there is nothing of the appropriate type to
  process, XtAppProcessEvent blocks until there is.  If there is more than
  one type of thing available to process, it is undefined which will get
  processed. Usually, this procedure is not called by client applications
  (see XtAppMainLoop).	XtAppProcessEvent processes timer events by calling
  any appropriate timer callbacks, alternate input by calling any appropriate
  alternate input callbacks, signal source by calling any appropriate signal
  callbacks, and X events by calling XtDispatchEvent.

  When an X event is received, it is passed to XtDispatchEvent, which calls
  the appropriate event handlers and passes them the widget, the event, and
  client-specific data registered with each procedure.	If there are no
  handlers for that event registered, the event is ignored and the dispatcher
  simply returns. The order in which the handlers are called is undefined.

  The XtDispatchEvent function sends those events to the event handler
  functions that have been previously registered with the dispatch routine.
  XtDispatchEvent returns True if it dispatched the event to some handler and
  False if it found no handler to dispatch the event to. The most common use
  of XtDispatchEvent is to dispatch events acquired with the XtAppNextEvent
  procedure. However, it also can be used to dispatch user-constructed
  events.  XtDispatchEvent also is responsible for implementing the grab
  semantics for XtAddGrab.

  The XtAppMainLoop function first reads the next incoming X event by calling
  XtAppNextEvent and then it dispatches the event to the appropriate
  registered procedure by calling XtDispatchEvent. This constitutes the main
  loop of X Toolkit applications, and, as such, it does not return.
  Applications are expected to exit in response to some user action. There is
  nothing special about XtAppMainLoop; it is simply an infinite loop that
  calls XtAppNextEvent and then XtDispatchEvent.

  Applications can provide their own version of this loop, which tests some
  global termination flag or tests that the number of top-level widgets is
  larger than zero before circling back to the call to XtAppNextEvent.

SEE ALSO
  X Toolkit Intrinsics -- C Language Interface

  Xlib -- C Language X Interface

Index for Section 3Xt

Alphabetical listing for X

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