NAME

GET LOCATOR − retrieve the 2D components of the LOCATOR event in the PHIGS current event report

SYNOPSIS

C Syntax

void
pget_loc ( view_ind, loc_pos )
Pint∗view_ind;OUT view index
Ppoint∗loc_pos;OUT locator position

Required PHIGS Operating States

(PHOP, WSOP, ∗, ∗)

DESCRIPTION

Purpose

GET LOCATOR retrieves the current event report from the PHIGS state list when the event report contains a Locator event.  A LOCATOR event consists of a position and a view index.  The position is the World Coordinate (WC) point corresponding to the position on the workstation selected by the operator.  The view index is the index of the view representation used to transform the selected position from Normalized Projection Coordinates (NPC) to WC. 

C Output Parameters

view_ind
PHIGS sets the variable pointed to by view_ind to the index of the view representation used to transform the NPC locator position to a WC position. 

loc_pos
PHIGS sets the variable pointed to by loc_pos to the 2D world coordinate locator position corresponding to the device coordinate position selected by the operator.  Ppoint is defined in phigs.h as follows:

typedef struct {
Pfloatx;/∗ x coordinate ∗/
Pfloaty;/∗ y coordinate ∗/
} Ppoint;

Execution

When an input device in Event mode is triggered by the operator, an event report is added to the input event queue.  The event report contains the identity and current measure of the device.  AWAIT EVENT moves the measure of the oldest event in the input queue to the current event report in the PHIGS state list.  If the event is a Locator event, GET LOCATOR or GET LOCATOR 3 is used to retrieve the contents of the event from the current event report. 

The LOCATOR position is computed by mapping the DC workstation position selected by the operator to a WC point.  The workstation transform is used to transform the DC position to a NPC position prior to transforming it to WC.  See INITIALIZE LOCATOR and SET VIEW TRANSFORMATION INPUT PRIORITY for a description of how PHIGS determines the view representation to use to map the NPC position to WC. 

See INITIALIZE LOCATOR for a description of the available LOCATOR devices and how their measure values are determined. 

ERRORS

003Ignoring function, function requires state (PHOP, WSOP, ∗, ∗)

259Ignoring function, the input device class of the current input report does not match the class being requested

SEE ALSO

INITIALIZE LOCATOR (3P)
AWAIT EVENT (3P)
GET LOCATOR 3 (3P)
SET VIEW TRANSFORMATION INPUT PRIORITY (3P)

September 02, 1992