DtActionCallbackProc(library call) DtActionCallbackProc(library call)
NAMEDtActionCallbackProc — notify application that the status of an appli‐
cation has changed
SYNOPSIS
#include <Dt/Action.h>
DESCRIPTION
The Dt/Action.h header defines the DtActionCallbackProc callback proto‐
type as follows:
typedef void (*DtActionCallbackProc)(DtActionInvocationID id,
XtPointer client_data,
DtActionArg *args,
int argCount,
DtActionStatus status);
If registered when invoking an action with DtActionInvoke(3), a DtAc‐
tionCallbackProc procedure is called whenever an action has a status
update, such as action termination. Depending on status, modified
action arguments may be returned using args.
The id argument specifies an invocation ID as returned by DtActionIn‐
voke(3).
The client_data argument specifies the client data that was registered
with DtActionInvoke(3).
The args argument is an array of updated action argument structures, if
there are any. Individual arguments have their argClass set to one of
the standard argument classes, or DtACTION_NULLARG, to indicate that
the current status update is not providing an update for the given
argument. If the object has been removed (for example, dropped on the
trash), the return argClass is set to DtACTION_NULLARG to indicate that
it no longer exists.
The args array has been allocated by XtMalloc(3), as have any of the
char* or void* elements contained in each of the args. The application
is responsible for calling XtFree(3) on all elements contained in each
of the args, and then calling XtFree(3) on args.
The argCount argument specifies the total number of arguments in args.
This number equals the number of arguments originally provided to DtAc‐
tionInvoke(3)
The nth argument in the original action argument array corresponds to
the nth argument in an updated action argument array.
The status argument specifies the purpose of the status update. The
status codes listed here and in Dt/Action.h - DtAction(5), may be
returned in a DtActionCallbackProc:
DtACTION_INVOKED
The corresponding DtActionInvoke(3) which is asynchronous and
does not block when starting actions, has finished starting
the requested actions. For all DtActionInvoke(3) calls that
include a DtactionCallbackProc, this status code is guaran‐
teed to be returned. When returned, no additional prompts
for data will appear from the action service.
DtACTION_DONE
The actions that were the result of the original DtActionIn‐
voke(3) call have terminated normally. Once this status
value is returned, all registered callbacks are invalidated,
and id can no longer be used in subsequent action service
calls. Returned args data may accompany the DtACTION_DONE
status code. For all DtActionInvoke(3) calls that include a
DtActionCallbackProc, this status code or an equivalent sta‐
tus code (for example, DtACTION_CANCELED or DtACTION_FAILED)
is guaranteed to be returned.
DtACTION_CANCELED
The actions that were the result of the original DtActionIn‐
voke(3) call were canceled and have terminated normally.
Once this status value is returned, all registered callbacks
are invalidated, and id can no longer be used in subsequent
action service calls. No args data will accompany the DtAC‐
TION_CANCELED status code.
DtACTION_FAILED
An error occured and a normal termination is no longer possi‐
ble. The action service may have failed to start the action
or lost contact with and abandoned the action. Once this
status value is returned, an error dialog may be posted by
the action service, all registered callbacks are invalidated,
and id can no longer be used in subsequent action service
calls. No args data will accompany the DtACTION_FAILED sta‐
tus code.
DtACTION_STATUS_UPDATE
The actions associated with id have generated a status
update, such as returning modified args. Updates occur in
several ways.
If several actions were started from a single DtActionIn‐
voke(3), then as each individual action terminates, a DtAC‐
TION_STATUS_UPDATE with return args is returned, and when the
final action terminates, a DtACTION_DONE or equivalent status
code is returned, possibly with return arguments.
Other actions may have the capability to generate updates
(for example, Tooltalk-based actions doing a Media Exchange
Deposit (Request)).
In most cases, a DtActionArg argument array accompanying a
DtACTION_STATUS_UPDATE only has updated data for a few of the
arguments; the remaining arguments are set to DtAC‐
TION_NULLARG.
EXAMPLES
The following shows how a DtActionCallbackProc might be coded.
DtActionCallbackProc myCallback(
DtActionInvocationID id,
XtPointer client_data,
DtActionArg *actionArgPtr,
int actionArgCount,
DtActionStatus status);
{
extern DtActionArg *myUpdatedArgs; /* global hook for new data */
extern int myDoneFlag; /* global done flag */
switch (status) {
case DtACTION_INVOKED:
/*
* All the arguments to the original DtActionInvoke
* have been consumed by actions, and the actions have
* been started. Among other things, we will not see
* any more prompts for user input.
*/
break;
case DtACTION_DONE:
myUpdatedArgs = (DtActionArg *) actionArgPtr;
myDoneFlag = TRUE;
break;
case DtACTION_CANCELED:
case DtACTION_FAILED:
if ((actionArgCount != 0) && actionArgPtr) {
/*
* If not a normal shutdown, throw away returned
* information.
*/
for (i=0; i < actionArgCount; i++) {
if (actionArgPtr[i].argClass == DtACTION_FILE) {
XtFree(actionArgPtr[i].u.file.name);
} else if (actionArgPtr[i].argClass ==
DtACTION_BUFFER) {
XtFree(actionArgPtr[i].u.buffer.bp);
XtFree(actionArgPtr[i].u.buffer.type);
XtFree(actionArgPtr[i].u.buffer.name);
}
}
XtFree(actionArgPtr);
}
myUpdatedArgs = (DtActionArg *) NULL;
myDoneFlag = FALSE;
break;
case DtACTION_STATUS_UPDATE:
myUpdatedArgs = (DtActionArg *) actionArgPtr;
myDoneFlag = FALSE;
break;
default:
/* ignore */
break;
}
}
SEE ALSO
Dt/Action.h - DtAction(5), DtDbLoad(3), DtActionLabel(3), DtActionDe‐
scription(3), DtActionExists(3), DtActionInvoke(3), XtMalloc(3),
XtFree(3), dtdtfile(4).
DtActionCallbackProc(library call)