Tk_DoWhenIdle

Tk_DoWhenIdle(proc, clientData)

Tk_CancelIdleCall(proc, clientData)

ARGUMENTS

Tk_IdleProc *proc (in)

Procedure to invoke.

ClientData clientData (in)

Arbitrary one-word value to pass to proc.

Tk_DoWhenIdle arranges for proc to be invoked
when the application becomes idle. The application is
considered to be idle when Tk_DoOneEvent has been
called, it couldn't find any events to handle, and it is about
to go to sleep waiting for an event to occur. At this
point all pending Tk_DoWhenIdle handlers are
invoked. For each call to Tk_DoWhenIdle there will
be a single call to proc; after proc is
invoked the handler is automatically removed.
Tk_DoWhenIdle is only useable in programs that
use Tk_DoOneEvent to dispatch events.

Proc should have arguments and result that match the
type Tk_IdleProc:

typedef void Tk_IdleProc(ClientData clientData);

Tk_CancelIdleCall may be used to cancel one or more previous calls to Tk_DoWhenIdle: if there is a Tk_DoWhenIdle handler registered for proc and clientData, then it is removed without invoking it. If there is more than one handler on the idle list that refers to proc and clientData, all of the handlers are removed. If no existing handlers match proc and clientData then nothing happens.

Tk_DoWhenIdle is most useful in situations where (a) a piece of work will have to be done but (b) it's possible that something will happen in the near future that will change what has to be done, or require something different to be done. Tk_DoWhenIdle allows the actual work to be deferred until all pending events have been processed. At this point the exact work to be done will presumably be known and it can be done exactly once.

For example, Tk_DoWhenIdle might be used by an editor to defer display updates until all pending commands have been processed. Without this feature, redundant redisplays might occur in some situations, such as the processing of a command file.

KEYWORDS