How to make a Gtk::IconView recompute and repaint its columns

[Todor Todorov <ttodorov gmx net>]

Hello list,

I have a Gtk::IconView and a custom cell renderer for displaying 
thumbnails. The cell renderer overrides the default size and paint 
vfuncs and computes size/paints with regard to a current zoom value. The 
relevant parts in the cell renderer are:

<code>
private:
    Glib::Property< gdouble >  propertyZoom;
public:
    Glib::PropertyProxy< gdouble >  property_thumb_zoom() { return 
propertyZoom.get_proxy(); }
</code>

When the zoom changes via a slider, I do something like:

<code>
    m_pCell->property_thumb_zoom() = slider->get_value();
    m_pIconView->queue_draw();
</code>

That works OK with one exception: The cell render computes the new size 
correctly and the thumbnails are redrawn according to the new zoom 
value, but the icon view itself still paints the same number of columns 
as it started out originally. Which makes icons encroach each others 
space in case of zooming in, or way too big spaces between columns in 
case of zooming out.

Any ideas how to fix that? Help is greatly appreciated.

Best regards,

Todor