REQUEST_LOCATOR(3G)

NAME

request_locator − wait for a measure to be triggered, then return the 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);

HP-UX COMPATIBILITY

Level: HP-UX/STANDARD

Origin: ANSI Computer Graphics Interface

DESCRIPTION

INPUT PARAMETERS

fildes
is an integer file descriptor returned by gopen when an I/O path to a graphics device is opened.
ordinal
a logical device number ranging from 1 to number of devices of this class.
timeout
is the time, in seconds, to wait for a trigger.

OUTPUT PARAMETERS

valid
is set to FALSE (0) if data is invalid, that is, if a break occurs, if the timeout period is exceeded, or if the device is not initialized. If valid is set to FALSE, then (x,y,z) is undefined. If set to TRUE (1), then the data is valid.
x,y,z
is set to the 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 the locator is triggered, when the user indicates a ’break’ action, or 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 may 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.

Whether a previously posted request is ready can be read with inquire_request_status.

A previously posted and satisfied but not read request can be discarded by issuing a request_locator with a zero timeout, and discarding the result.

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