anchor.diff:  
   clear_canvas(S) ->
       DC = wxClientDC:new(S#state.canvas),
  +    wxDC:setBackground(DC, ?wxWHITE_BRUSH), %% Needed on mac
       wxDC:clear(DC),
       {CanvasW, CanvasH} = wxPanel:getSize(S#state.canvas),
       wxSizer:recalcSizes(S#state.canvas_sizer),
  
positive.code: 		[{flag, ?wxEXPAND}]),
  
      CanvasSizer = wxBoxSizer:new(?wxHORIZONTAL),
      Canvas = wxPanel:new(Panel, []),
      {CanvasW,CanvasH} = wxPanel:getSize(Canvas),
      ScrollBar = wxScrollBar:new(Panel, ?wxID_ANY, [{style, ?wxSB_VERTICAL}]),
  
  
negative.code:     wxPanel:connect(Canvas, left_up),
      wxPanel:connect(Canvas, right_up),
      wxPanel:connect(Canvas, size),
      Self = self(),
      wxPanel:connect(Canvas, paint, [{callback,  %% Needed on windows
  				     fun(Ev, _) -> 
  					     DC = wxPaintDC:new(Canvas),
  					     wxPaintDC:destroy(DC),
  					     Self ! Ev
  				     end}]),
      wxPanel:connect(Canvas, key_down),
      wxPanel:connect(Canvas, kill_focus),
      wxPanel:connect(Canvas, enter_window, [{skip, true}]), 
  