Auto scroll a gtkscrolledwindow

Question

I have a form interface with a large number of horizontal drop down and text boxes that are inside a GTKscrolledWindow. The form has to be aligned horizontally because there are an unlimited number of forms in the window (think tabel of forms).

Is it (possible/how do I) auto-scroll the GTKScrolledWindow to the right when the operator tabs to the next form control which is off to the right of the screen.?

Related question would be how do I detect if the focused element (button etc) is visible in it's parent scrolledwindow.

Thanks.

Answer 1

Here's what I did, based on Michy's answer.

To make a scrolled window auto-scroll, run in the constructor:

FocusScroll(scrolledwindow).

    class FocusScroll(object):
    """
    Get a gtk.ScrolledWindow which contains a gtk.Viewport.
    Attach event handlers which will scroll it to show the focused widget.
    """
    def __init__(self, scrolledwindow):
        self.scrolledwindow = scrolledwindow
        self.viewport = scrolledwindow.get_child()
        assert isinstance(self.viewport, gtk.Viewport)
        self.main_widget = self.viewport.get_child()
        self.vadj = scrolledwindow.get_vadjustment()
        self.window = self.get_window(scrolledwindow)

        self.viewport.connect('set-focus-child', self.on_viewport_set_focus_child)

    def get_window(self, widget):
        if isinstance(widget, gtk.Window):
            return widget
        else:
            return self.get_window(widget.get_parent())

    def is_child(self, widget, container):
        """
        Go recursively over all children of container, to check if widget is
        a child of it.
        """
        for child in container.get_children():
            if child is widget:
                return True
            elif isinstance(child, gtk.Container):
                if self.is_child(widget, child):
                    return True
        else:
            return False

    def on_viewport_set_focus_child(self, _viewport, _child):
        idle_add(self.scroll_slide_viewport)

    def scroll_slide_viewport(self):
        """Scroll the viewport if needed to see the current focused widget"""
        widget = self.window.get_focus()
        if not self.is_child(widget, self.main_widget):
            return

        _wleft, wtop = widget.translate_coordinates(self.main_widget, 0, 0)
        wbottom = wtop + widget.get_allocation().height

        top = self.vadj.value
        bottom = top + self.vadj.page_size

        if wtop < top:
            self.vadj.value = wtop
        elif wbottom > bottom:
            self.vadj.value = wbottom - self.vadj.page_size