func calibratePoint(et gaze.EyeTracker, x, y float64) {
termbox.Clear(0, 0)
sizeX, sizeY := termbox.Size()
dx, dy := int(float64(sizeX)*x), int(float64(sizeY)*y)
termbox.CellBuffer()[sizeX*dy+dx] = termbox.Cell{'#', marker, termbox.ColorDefault}
termbox.Flush()
//log.Printf("Termbox Size: (%d, %d)", sizeX, sizeY)
log.Printf("Calibrating (%.3f, %.3f)", x, y)
done := make(chan struct{})
time.Sleep(1 * time.Second) //Minimum time. Gives user time to react.
et.AddPointToCalibration(gaze.NewPoint2D(x, y), func(err error) {
close(done) //Synchronizing async call.
})
<-done
}
