changing hue loop length

Changing the hue loop length without compensation causes distracting jumps in hue. Reflecting the hue position prevents jumps entirely when the loop length is increased, and minimizes the probability of a jump when the loop length is decreased. Without changing the base position, it's impossible to prevent jumps entirely in the latter case, because the current hue may no longer fall within the range of the loop.

if (m_st.HueLoop && m_st.HueLoopLength) // try to avoid hue jump
 m_st.HueLoopPos = Reflect(m_st.HueLoopPos, m_st.HueLoopLength);
m_st.HueLoopLength = Length;