track(3G)

NAME

track − asynchronously echo an input device’s locator position on an output device.

SYNOPSIS

C Syntax:

void track ( indev, outdev, locator_num );
int indev, outdev, locator_num;

FORTRAN77 Syntax:

subroutine track ( indev, outdev, locator_num )
integer*4 indev, outdev, locator_num

Pascal Syntax:

procedure track ( indev, outdev, locator_num:integer );

DESCRIPTION

Input Parameters

indev File descriptor for the input device whose locator subdevice is to be tracked.

outdev File descriptor for the output device whose echo is to be used to track the input device.

locator_num Number of the locator subdevice on the specified input device whose position is to be tracked (the number of locators on a device may be obtained using the inquire_input_capabilities procedure).

Discussion

track sets up asynchronous tracking of an input device’s locator position onto an output device’s view surface. The locator position in virtual device coordinates (VDC) is mapped onto the virtual device coordinates of the output device. If the VDC extents of the two devices are not similar, the tracking movement will be either exaggerated or reduced.

When done tracking, track_off(3G) should be called. This turns off the tracking daemon and cleans up the kernel IPC resources (shared memory, semaphores, messages) that the tracking process uses to communicate with the running Starbase program.

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