Author: Tomas Rutkauskas

I want the cell in a TStringGrid to flash for a few seconds when its value changes 
(as a result of some outside monitored process for example). How would I do that?

Answer:

One way would be to check the contents of the cell against the previous value in 
the OnDrawCell event. When it has changed, start a timer which invalidates the grid 
on a set interval. Below you'll find an example for just one cell.

1   {Somewhere in the private section of the form}
2   var
3     FToggleCount: integer;
4     FCheckstring: string;
5   
6   implementation
7   
8   procedure TForm1.Timer1Timer(Sender: TObject);
9   begin
10    Inc(FToggleCount);
11    if FToggleCount >= 10 then
12      Timer1.Enabled := False;
13    StringGrid1.Invalidate;
14  end;
15  
16  procedure TForm1.StringGrid1DrawCell(Sender: TObject; ACol, ARow: Integer;
17    Rect: TRect; State: TGridDrawState);
18  var
19    s: string;
20  begin
21    if (ACol = 1) and (ARow = 1) then
22      with Sender as TStringGrid do
23      begin
24        s := Cells[ACol, ARow];
25        if s <> FCheckstring then
26        begin
27          FCheckstring := s;
28          FToggleCount := 0;
29          Timer1.Enabled := True;
30        end;
31        if Timer1.Enabled and ((FToggleCount mod 2) = 0) then
32        begin
33          Canvas.Brush.Color := clRed;
34          Canvas.FillRect(Rect);
35          Canvas.TextOut(Rect.Left + 2, Rect.Top + 2, s);
36        end;
37      end;
38  end;