Author: Tomas Rutkauskas

Is there any way to tell within the OnEnter handler of Control2, which other 
control just passed the focus to Control2?

Answer:

1   type
2     TForm1 = class(TForm)
3       { ... }
4     public
5       LastControl: TComponent;
6     end;
7   
8   procedure TForm1.Edit1OnEnter(Sender: TObject);
9   begin
10    if Assigned(LastControl) then
11      { do whatever you want with the previous control }
12      LastControl := Sender as TComponent;
13  end;
14  
15  procedure TForm1.FormCreate(Sender: TObject);
16  begin
17    LastControl := nil;
18  end;