[Lmuse-developer] how to follow the song

[Florian J. <flo...@we...>]

Hi

i want to make my score editor follow the song while playing
i found that song->posChanged(int idx, unsigned tick, bool 
updateScrollBar) is responsible for doing this
i also found out that song and canvas are keeping an array pos[3], and 
idx can be 0,1 or 2
i saw lines like emit posChanged(0, pos[0], ...) etc.

i still have two questions:

what does updateScrollBar do? i mean, if i do NOT update it, nothing 
should happen and the signal should be unneccessary?

and why are three positions kept? which of them do i want to use?

greetings
flo