[Vala] Newbie help requested for scrolling a TextView

[Manish Jain <jude obscure yandex com>]

Hi,

I am C programmer trying to  pick up Vala fundamentals.

I am stuck in a small project to programmatically scroll a 
Gtk.TextView widget embedded in a Gtk.ScrolledWindow.

The scrollable view widget displays a text file read at run time.

I would like to the view's current contents to be controlled with a 
vertical scale: when v_scale slider is 0, the view shows the beginning 
of the file, and when v_scale slider is close to 100, the view shows the 
last few characters/lines in the file.

Despite a lot of effort to write an event handler, I still cannot get 
the scale to tell the view to scroll. I have tried scrolling with the
scroll_to_iter() method, but the iterator always lands me at the top of 
the file, whereas I want the view to move south.

Can somebody please tip me how to control the view's position with the 
vertical scale in Vala ?

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Thanks & Regards,
Manish Jain