As second part to reduce flikkery, I have reduce it by a little code change in file:
I don't know why is it there the point of interest, but it worked for me.
The position for the change is near the lines: 1464, and 1477: (I comment the lines with C++ style comment's):
The reason for this was, that the Win32API function InvalidateRect force a full repaint of the control, so it was called twice (which costs cpu times). And in this case - it was the mouse cursor on the desktop, starting with the welcome window.
have a nice coding