is it intended that the window base time starts the amount of the windows size in front of the current price? for example the standard of 100 draws the lines for a range of 200 bars. If you would divide the _length of the base_t by the window size like shown below it would start at the current price time.
// || Function to draw base lines on chart.
int _base_t = time + int(change(time) * _length/window)
int _start_t = time - int(change(time) * _length)