DtActionCallbackProc(library call) DtActionCallbackProc(library call)
NAME
DtActionCallbackProc -- notify application that the status of an application has changed
SYNOPSIS
#include <Dt/Action.h>
DESCRIPTION
The Dt/Action.h header defines the DtActionCallbackProc callback prototype 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 DtActionCallbackProc 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 DtActionInvoke(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
DtActionInvoke(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 guaranteed 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 DtActionInvoke(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 status code (for example, DtACTION_CANCELED or DtACTION_FAILED) is guaranteed to be returned.
DtACTION_CANCELED
The actions that were the result of the original DtActionInvoke(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 DtACTION_CANCELED status code.
DtACTION_FAILED
An error occured and a normal termination is no longer possible. 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 status 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 DtActionInvoke(3), then as each individual action terminates, a DtACTION_STA-
TUS_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 argu-
ments; the remaining arguments are set to DtACTION_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), DtActionDescription(3), DtActionExists(3), DtActionInvoke(3), XtMalloc(3),
XtFree(3), dtdtfile(4).
DtActionCallbackProc(library call)