Gtk.TextView does not scroll

[kaschpal (Ulrich Leutner)]

Hello,

in my application I have several TextViews aligned in a grid horizontally. They all scroll syncronous (to my surprise) this works automatically.
Now i want at a certain keyboard shortcut, to jump the cursor to a line number and select the line. This also works. What does not work is to scroll to this line. My code looks like this:

            # to sequence view to class
            self.parent.parent.window.stack.set_visible_child_name("sequence")
            nb.switch_to_tab(class_name)

            # focus
            tab = nb.get_tab(class_name)
            tv = tab.sequenceTextView
            tv.grab_focus()

            # set postion in textfield
            buf = tab.sequenceBuf
            cursor = buf.get_iter_at_line(position)
            res = tv.scroll_to_iter(cursor, 0.0, True, 0.5, 0.5)
            buf.place_cursor(cursor)

            # select line
            line_begin = buf.get_iter_at_line(position) # again, since forward_to_line does not return a copy
            cursor.forward_to_line_end()
            buf.select_range(line_begin, cursor)


            # scroll
            tv.scroll_mark_onscreen(buf.get_insert())

Except to the last line everything works fine.
I tried virtually anything: scroll to an iter, scroll the first textview added to the grid, scroll to cursor.
Also I get no warning which helps. With the (test) line

            res = tv.scroll_to_iter(cursor, 0.0, True, 0.5, 0.5)

above, I got as return code False, which is indeed correct. But I still can’t figure out, why.

Thanks in advance!

Ulrich