REQUEST_LOCATOR(3G)

NAME

request_locator − wait for measure to be triggered then return measured value

SYNOPSIS

C Syntax:

void request_locator(fildes,ordinal,timeout,valid,x,y,z);
int fildes,ordinal,*valid;
float timeout,*x,*y,*z;

FORTRAN77 Syntax:

subroutine request_locator(fildes,ordinal,timeout,
valid,x,y,z)
integer*4 fildes,ordinal,valid
real timeout,x,y,z

Pascal Syntax:

procedure request_locator(fildes,ordinal:integer;
timeout:real;var valid:integer;var x,y,z:real);

DESCRIPTION

Input Parameters

fildes Integer file descriptor returned by gopen when an I/O path to a graphics device is opened.

ordinal Logical device number ranging from 1 to number of devices of this class.

timeout Time, in seconds, to wait for a trigger.

Output Parameters

valid TRUE (1 in Pascal) if data is valid.

FALSE (0 in Pascal) if data is invalid (timeout period exceeded or device not initialized). If FALSE, x,y,z is undefined.

(x,y,z) Set to x, y, and z Virtual Device Coordinate values of the point returned from a locator device.

Discussion

Request_locator returns the measure value of the device specified by fildes and ordinal when a trigger occurs, or when when the time period specified by timeout is exceeded. If the request was not previously posted with initiate_request and no request data is ready for this device, it is posted by this call. If a request was previously posted but not yet satisfied, the timeout runs from the time this call was made.

A request can be performed on an input device while it is enabled for event generation. The mode of (events enabled/events disabled) is saved by the device and restored after the request has been satisfied. The request data does not go into the event queue, but into a separate virtual register.

Use inquire_request_status. to determine whether a previously posted request is ready.

To discard a request that was previously posted and satisfied, but which has not been read, use request_choice with a zero timeout and discard the result.

Museum