On 6/11/21 8:03 AM, Greg Ercolano wrote:

    If you parented FLTK widgets to items using Fl_Tree_Item::widget(),
    to clear /those/, you can call: Fl_Tree::Fl_Group::clear(). So to clear the tree
    and all child FLTK widgets I think you'd need to use:

            tree->clear();
            tree->Fl_Group::clear();

    Actually, I take that back, that advice is bad as that clears Fl_Tree's
    child scrollbar widgets too, which Fl_Tree will not expect.

    To clear all the FLTK child widgets (without clearing the scrollbars),
    Fl_Tree should really provide a method to clear the FLTK child widgets
    along the lines of:

  // Clear all items and FLTK child widgets parented to the tree
  void Fl_Tree::clear_all() {
    clear(); // clears the items
    Fl_Group::remove(_vscroll);
    Fl_Group::remove(_hscroll);
    Fl_Group::clear(); // clears all child fltk widgets except scrollbars
    Fl_Group::add(_vscroll);
    Fl_Group::add(_hscroll);
  }

    You can derive your own class from Fl_Tree and implement that method.
    That's the only way you can access the protected scrollbar members.

    Arguably Fl_Tree::clear() should clear the FLTK child widgets too,
    though there was a desire to allow the items to be cleared separately
    from FLTK widgets, and I don't think that was ever rectified in the API.

    Perhaps it's easier is to simply delete and recreate the Fl_Tree widget,
    as the Fl_Group base class will handle clearing the FLTK children.

    Anyway, all this is /only/ an issue if your app creates FLTK widgets
    and attaches them to the tree with Fl_Tree_Item::widget(w).