[Lazarus] TMemo flicker

[José Mejuto]

El 30/04/2013 10:31, Michael Van Canneyt escribió:

>> Your solution of course is mutch faster but I thought seeing the
>> progress is important for Jürgen.
> In that case the beginupdate/endupdate is a total waste of CPU.
>

Hello,

The problem is that the behavior changes with the use of begin/end 
update, at least on Windows platform. Run attached code to test. Just 
create a form and add a button and a Memo and link the button OnClick 
with this code (better visible with a quite big Memo):

-------------------------------

procedure TForm1.Button1Click(Sender: TObject);
const
   TestMode=3; //CHANGE to 1..3 to run different tests
var
    i: integer;
begin
   for i := 1 to 40 do begin
     Memo1.Lines.add('Some lines at the beginning to watch the up/down 
flicker effect.');
   end;
   if TestMode=1 then begin
     for i := 1 to 1000 do begin
       Memo1.Lines[Memo1.lines.Count-1]:='#### '+IntToStr(i);
     end;
   end else if TestMode=2 then begin
     for i := 1 to 1000 do begin
       Memo1.Lines.BeginUpdate;
       Memo1.Lines[Memo1.lines.Count-1]:='#### '+IntToStr(i);
       Memo1.Lines.EndUpdate;
     end;
   end else if TestMode=3 then begin
     for i := 1 to 1000 do begin
       Memo1.Lines.BeginUpdate;
       Memo1.Lines[Memo1.lines.Count-1]:='#### '+IntToStr(i);
       Memo1.Lines.EndUpdate;
       Application.ProcessMessages;
     end;
   end;
end;
--------------------------------

If Begin/End update is being used the vertical scroll bar position is 
not updated, I do not know if this is expected :-?

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