Gtk Scrolledwindow with a textview inside still has a limited nr of lines

[ldries46 <bertus.dries@planet.nl>]

In my application Gtk_ScrolledWindow with a Textview inside still has a 
limited nr of lines.
Putting in a document of a 50 lines I can See all lines within the window.
Expanding the document to about 100 lines I see about 70 lines without 
scrolling and the rest I can see by scrolling.
Expanding the document with another 100 lines I still can see about 70 
lines but by scrolling I can only see the lines 71 till 130. The last 70 
are not to be reached.  checked if this has anything to do with my 
program and the only thing I can think of is that I somewhere during the 
program Delete the entries (may somewhere around 120 to 130 lines) up to 
than and refill it with the 200 a talked about before. Does that has 
anything to do with it . If so How can I reset the window, if not where 
can I specify an indefinite number of lines