anchor.diff:  - - - - - - - - - - - - - - - - -
   Author: Zoran Vučenović, January and February 2010
           Зоран Вученовић, јануар и фебруар 2010.
  -
  -Last change: August 2012.
   
      This unit is part of ZVDateTimeCtrls package for Lazarus. It contains
   component and property editors for TZVDateTimePicker control.
  
positive.code: 
    L, T, W, H: Integer;
    R: TRect;
  begin
    if Assigned(Caller) then begin
      CallerZVDateTimePicker := Caller;
  
negative.code: 
      H := 2 * ZVDateTimePickerMax.Height + LabelNull.Height + ButtonPanel.Height + 58;
  
      M := Screen.MonitorFromWindow(CallerZVDateTimePicker.Handle);
  
      R := M.WorkareaRect;
      // But if WorkareaRect doesn't work (not implemented for all widgetsets),
      // then take BoundsRect:
      if (R.Right <= R.Left) or (R.Bottom <= R.Top) then
        R := M.BoundsRect;
  
      L := (R.Left + R.Right - W) div 2;
      T := (R.Top + R.Bottom - H) div 2;
  
  