ECHO_UPDATE(3G)

NAME

echo_update − change output device’s echo position

SYNOPSIS

C Syntax:

void echo_update(fildes,echo_number,x,y,z);
int fildes,echo_number;
float x,y,z;

void dcecho_update(fildes,echo_number,dcx,dcy);
int fildes,echo_number,dcx,dcy;

FORTRAN77 Syntax:

subroutine echo_update(fildes,echo_number,x,y,z)
integer*4 fildes,echo_number
real x,y,z

subroutine dcecho_update(fildes,echo_number,dcx,dcy)
integer*4 fildes,echo_number,dcx,dcy

Pascal Syntax:

procedure echo_update(fildes,echo_number:integer;
x,y,z:real);
procedure dcecho_update(fildes,echo_number,dcx,dcy:integer);

DESCRIPTION

Input Parameters

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

echo_number Selects the particular echo to be moved if the graphics device supports more than one simultaneous echo. For single-echo devices, use 0 (zero).

x,y,z Defines the updated echo position in Virtual Device Coordinates.

dcx,dcy Defines the updated echo position in Device Coordinates.

Discussion

Echo_update defines an updated echo position for the echo number specified. For echo types that use one stationary point and one moving point determined by the input device’s location, such as rubber-band-line echo, this updated position is used as the moving point. The initial position set with the echo_type command is then used as the base point of the echo.

If tracking is on, echo_update has little effect on echo position because the tracking process moves it to the current locator position very soon.

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