Re: [wxCode-users] wxTreeListCtrl scrollbar question...

[Carl G. <cg...@gm...>]

On 11/23/05, Otto Wyss <ott...@or...> wrote:
> Carl Godkin wrote:
>
> >When I create the control and populate it with more items than fit verti=
cally,
> >I don't get a scrollbar right away until I click on one of the items.  T=
his
> >happens both on Windows and Linux so I presume it's intentional.  Howeve=
r,
> >I'd like to always show the vertical scrollbar so that the user knows th=
ere are
> >more items below.
> >
> >
> >
> I've seen this as well lately and think it's something wrong within
> wxWidgets but I'm not sure. I haven't seen it in any of my old apps,
> only in the new TorMgr I write for the Tor GUI contest. So it might be a
> problem of 2.6.2, again I'm not sure.
>
> >Is there some way I can force this?

I looked into this and found the problem, I think.

The member function wxTreeListMainWindow::AdjustMyScrollbars()
calls GetSize() on the root item.  However wxTreeListItem::GetSize()
doesn't think the root item is expanded, so all you get is the (hidden)
root item's size.

I worked around this by adding Expand(rootId) after I populate the tree
initially and now the vertical scrollbar appears as I think it should.

This even makes sense to me.  I wondered if this problem would
happen in the generic tree control which was apparently  the model
for the tree list control but found that there is a little code we might wa=
nt
to add to avoid this problem.  Notice the difference here:

void wxTreeListMainWindow::SetWindowStyle (const long styles) {
    // right now, just sets the styles.  Eventually, we may
    // want to update the inherited styles, but right now
    // none of the parents has updatable styles
    m_windowStyle =3D styles;
    m_dirty =3D true;
}


void wxGenericTreeCtrl::SetWindowStyle(const long styles)
{
    if (!HasFlag(wxTR_HIDE_ROOT) && (styles & wxTR_HIDE_ROOT))
    {
        // if we will hide the root, make sure children are visible
        m_anchor->SetHasPlus();
        m_anchor->Expand();
        CalculatePositions();
    }

    // right now, just sets the styles.  Eventually, we may
    // want to update the inherited styles, but right now
    // none of the parents has updatable styles
    m_windowStyle =3D styles;
    m_dirty =3D true;
}

(Note that m_anchor in the generic tree control is the same as m_rootItem
in the tree list control.)

Thanks,

carl