title: wxFrame does not process Tab button
body: <p>I have a simple wxFrame with 3 buttons. After I press Tab nothing happens. In the forum I found that wxFrame should process Tab button events normally and switch focus between controls. I tried with wxTAB_TRAVERSAL and without it, but look like no result.</p>
  
  <p>Here is my code. wxWidgets 3.0.2. Please, help.</p>
  
  <pre><code>class TabWnd
      : public wxFrame
  {
  public:
      TabWnd()
          : wxFrame(nullptr,
                    wxID_ANY,
                    wxEmptyString,
                    wxDefaultPosition,
                    wxDefaultSize,
                    wxDEFAULT_FRAME_STYLE | wxTAB_TRAVERSAL)
      {
          wxBoxSizer* sz = new wxBoxSizer(wxVERTICAL);
  
          wxButton* b1 = new wxButton(this, wxID_ANY, wxT("First"));
          sz-&gt;Add(b1, 0, wxALL, 5);
  
          wxButton* b2 = new wxButton(this, wxID_ANY, wxT("Second"));
          sz-&gt;Add(b2, 0, wxALL, 5);
  
          wxButton* b3 = new wxButton(this, wxID_ANY, wxT("Third"));
          sz-&gt;Add(b3, 0, wxALL, 5);
  
          SetSizer(sz);
          Layout();
          Centre(wxBOTH);
      }
  };
  
  class WxguiApp
      : public wxApp
  {
  public:
      bool OnInit() override
      {
          TabWnd* mainWnd = new TabWnd();
          mainWnd-&gt;Show();
          SetTopWindow(mainWnd);
  
          return true;
      }
  };
  
  IMPLEMENT_APP(WxguiApp);
  </code></pre>