Title: Undo function with TMemo
Question: Several tasks can be solved by knowing the internal messages of the VCL.
Answer:
A undo function of TMemo can be best realized by useing the EM_UNDO message of the VCL:
procedure TForm1.ButtonUndoClick(Sender: TObject);
begin
Memo1.Perform(EM_UNDO, 0, 0);
end;
With EM_CANUNDO you can check if a undo is possible:
procedure TForm1.Timer1Timer(Sender: TObject);
begin
Button1.Enabled := Memo1.Perform(EM_CANUNDO, 0, 0) 0;
end;