hogging CPU breaks About dialog

If main is saturating the CPU, Help/About makes the app modal, but no dialog is displayed. The bug occurs with any dialog created via DoModal, but it does NOT occur with the common dialogs (e.g. CFileDialog), presumably because they use a different creation method. Help/About is currently the only non-common modal dialog accessible directly from the main menu, which is why the bug wasn't discovered earlier.

One workaround is to disable the main timer in CAboutDlg::OnInitDialog, and then re-enable it in ShowWindow. An easier one is to do an explicit ShowWindow in CAboutDlg::OnInitDialog.

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;