Function RideGetStartOfTrack

src/openrct2/ride/Ride.cpp:3925–3964

* Given a track element of the ride, find the start of the track. * It has to do this as a backwards loop in case this is an incomplete track. */

 * It has to do this as a backwards loop in case this is an incomplete track.
 */
void RideGetStartOfTrack(CoordsXYE* output)
{
    TrackBeginEnd trackBeginEnd;
    CoordsXYE trackElement = *output;
    if (trackBlockGetPrevious(trackElement, &trackBeginEnd))
    {
        TileElement* initial_map = trackElement.element;
        TrackBeginEnd slowIt = trackBeginEnd;
        bool moveSlowIt = true;
        do
        {
            // Because we are working backwards, begin_element is the section at the end of a piece of track, whereas
            // begin_x and begin_y are the coordinates at the start of a piece of track, so we need to pass end_x and
            // end_y
            CoordsXYE lastGood = {
                /* .x = */ trackBeginEnd.end_x,
                /* .y = */ trackBeginEnd.end_y,
                /* .element = */ trackBeginEnd.begin_element,
            };

            if (!trackBlockGetPrevious(
                    { trackBeginEnd.end_x, trackBeginEnd.end_y, trackBeginEnd.begin_element }, &trackBeginEnd))
            {
                trackElement = lastGood;
                break;
            }

            moveSlowIt = !moveSlowIt;
            if (moveSlowIt)
            {
                if (!trackBlockGetPrevious({ slowIt.end_x, slowIt.end_y, slowIt.begin_element }, &slowIt)
                    || slowIt.begin_element == trackBeginEnd.begin_element)
                {
                    break;
                }
            }
        } while (initial_map != trackBeginEnd.begin_element);
    }
    *output = trackElement;
}

/**
 *