if ( $key == WXK_TAB ){
    $this->FindWindow(Wx::XmlResource::GetXRCID('textCtrl_usr_input'))->AppendText('  ');
  }
  else{
        if($key >= 32 ){
      $this->FindWindow(Wx::XmlResource::GetXRCID('textCtrl_usr_input'))->AppendText(sprintf("%c", $key));
    }
  }