Scrolling to mark in TextView

[Andrew Krause <ajk265 psu edu>]

I have a Goto Line dialog that was working. What I did was get the line 
number, move the insert & selection_bound marks to that line and then 
scroll the TextView to the insert mark.

My problem is that the ScrolledWindow now contains a HBox. The HBox has 
a label that contains line numbering and the TextView. Now my Goto Line 
function does not work anymore. It moves the cursor but does not scroll 
to that mark. Also, when I type, if I press the Return key past the 
bottom of the buffer, it does not scroll down.

How can I fix this problem? Is there a way? Thank you for your help! - 
Andrew