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.ds b \s-2BREAK\s+2
.TH "REQUEST LOCATOR" 3P "29 February 1991"
.SH NAME
REQUEST LOCATOR \- request an operator interaction with a locator device
.IX "Locator Input Devices" "REQUEST LOCATOR"
.SH SYNOPSIS
.SS C Syntax
.ft B
.ta 1.25i 3i
.nf
void
preq_loc ( ws, dev, in_status, view_ind, loc_pos )
Pint	ws;	\fIworkstation identifier\fP
Pint	dev;	\fIlocator device number\fP
Pin_status	*in_status;	\fIOUT input status\fP
Pint	*view_ind;	\fIOUT view index\fP
Ppoint	*loc_pos;	\fIOUT locator position\fP
.fi
.ft R
.SS Required PHIGS Operating States
(PHOP, WSOP, *, *)
.SH DESCRIPTION
.SS Purpose
Use \s-2REQUEST LOCATOR\s+2 to request an operator interaction with a
specified locator device. The device must be in request mode. See
\s-2SET LOCATOR MODE\s+2 and \s-2INITIALIZE LOCATOR\s+2 for more information.
See the \fIAvailable Devices\fP section of \s-2INITIALIZE LOCATOR\s+2 for a
description of the available locator devices.
.LP
The request suspends \s-2PHIGS\s+2 until the specified device is triggered,
or the operator performs a \*b.
A \*b is performed by typing the \s-2CONTROL\s+2 and \s-2D\s+2 keys
simultaneously (^D).
.SS C Input Parameters
.IP \fIws\fP
Workstation identifier. An integer specifying the workstation with which
the requested locator device is associated.
.IP \fIdev\fP
The device number of the requested locator device.
See the \fIAvailable Devices\fP section of \s-2INITIALIZE LOCATOR\s+2 for a
description of the available locator devices.
.SS C Output Parameters
.IP \fIin_status\fP
A pointer to the location to store the status of the request.
Pin_status 
.sp .4
.ta .5i
.nf
typedef enum {
.sp .2
	PIN_STATUS_NONE,
	PIN_STATUS_OK,
	PIN_STATUS_NO_IN
.sp .2
} Pin_status;
.fi
.IP \fIview_ind\fP
A pointer to the location to store the view representation used to map
from Device Coordinates (\s-2DC\s+2) to World Coordinates (\s-2WC\s+2).
.IP \fIloc_pos\fP
A pointer to a Ppoint structure in which the system returns
the locator position coordinates.
Ppoint is defined in phigs.h as follows:
.sp .4
.nf
.ta .5i +\w'Pfloat	'u +\w'x;	'u
typedef enum {
.sp .2
	Pfloat	x;	/* x coordinate */
	Pfloat	y;	/* y coordinate */
.sp .2
} Ppoint;
.fi
.SS Execution
\s-2REQUEST LOCATOR\s+2 requests a logical input value from the specified
locator device. The specified device must be in request mode. See
\s-2SET LOCATOR MODE\s+2 for more information.
.LP
\s-2REQUEST LOCATOR\s+2 creates a measure
process for the specified device and suspends \s-2PHIGS\s+2 until the
device is triggered or the operator issues a \*b. 
A \*b is generated by the operator by depressing the Control and \s-2D\s+2 keys
simultaneously (^D).
.LP
If a \*b occurs, a status of \s-2PIN_STATUS_NO_IN\s+2 is returned and the locator data
is undefined.  If a status of \s-2PIN_STATUS_OK\s+2 is returned, the locator data is
available.  In either case, the measure process is then terminated and
\s-2PHIGS\s+2 processing resumes.
.LP
A locator measure consists of a \fIview_ind\fP and \fIloc_pos\fP.
The \fIview_ind\fP specifies the view representation from the workstation's
view table that was used to map the locator position from
Normalized Projections Coordinates (\s-2NPC\s+2) to \s-2WC\s+2.
The \fIloc_pos\fP is the position of the locator in \s-2WC\s+2.
\fBNote:\fP The \s-2\&2D\s+2 and \s-2\&3D\s+2
locator measure processes are the same except
that the \s-2\&2D\s+2 process discards the \fIz\fP coordinate. The \s-2\&3D\s+2
version of this
function, \s-2REQUEST LOCATOR 3\s+2, can be used if the value of the \fIz\fP
coordinate is needed.
.LP
See \s-2INITIALIZE LOCATOR\s+2 for a description of the available locator
devices.
.SH ERRORS
.IP 003
Ignoring function, function requires state 
(\s-2PHOP\s+2, \s-2WSOP\s+2, \s-2*\s+2, \s-2*\s+2)
.IP 054
Ignoring function, the specified workstation is not open
.IP 061
Ignoring function, specified workstation is neither of category \s-2INPUT\s+2
nor of category \s-2OUTIN\s+2
.IP 250
Ignoring function, the specified device is not available
on the specified workstation
.IP 251
Ignoring function, the function requires the input device
to be in \s-2REQUEST\s+2 mode
.SH SEE ALSO
.nf
.IP
.ta 0.5i
.SM "INITIALIZE LOCATOR (3P)"
.SM "SET LOCATOR MODE (3P)"
.SM "REQUEST LOCATOR 3 (3P)"
.SM "SET VIEW TRANSFORMATION INPUT PRIORITY (3P)"
.fi