Re: [Vala] Newbie help requested for scrolling a TextView

[Manish Jain <jude obscure yandex com>]

On 01/25/18 16:11, Al Thomas wrote:
> > On Thursday, 25 January 2018, 01:00:05 GMT, Manish Jain 
> <jude obscure yandex com> wrote:
>
> > 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.
>
> Have you tried moving the TextIter with something like:
> https://valadoc.org/gtk+-3.0/Gtk.TextIter.set_line.html
>
> It sounds like you want a TextIter instance for your vscale widget 
> that you can then move
> about the document and then scroll to it.
>
> It may be your almost there, just missing the last piece of the puzzle!
>
> Regards,
>
> Al

Hi Al/others,

The scrolling is beginning to happen, but not in the way I would expect.

Here is my event handler for the scale (which I am using a normal
command widget) :

    void scale_moved (Gtk.Range range)
    {
        TextIter iter = TextIter();

        view.get_iter_at_location(out iter, 0, ypos);
        view.scroll_to_iter(iter, 0, false, 0, 0);
        view.place_cursor_onscreen();
        ypos++;
    }

The ypos counter is initialized as 0, and then gets incremented
each time the scale is used. Effectively, each time the uses clicks
the scale, the view should move south one line. That is the behaviour
I would expect.

But the scrolling is almost negligible unless I jack up ypos argument
to get_iter_at_location() as 25*ypos - at which point the view moves
south sometimes one line or sometimes two lines.

I must be missing something: is the view scrolling somehow dependent
on window geometry and/or line lengths ? I would normally think the
ypos argument is just the number of newlines (minus one) to be skipped
when readjusting the view.

Thanks for any help.
Manish Jain