Scroll to a specific position.
scrollBy([in] int dx, [in] int dy)
This function is similar to scrollTo, except that it scrolls relative to the current position. A positive dx value scrolls right, a negative dx value scrolls left. Similarly, positive and negative dy values scroll down and up, respectively. For example:
viewer.scrollBy 5, -10
would scroll 5 pixels to the right and 10 pixels up from the current position.
viewer.scrollBy(-10, 0)