[Lazarus] TMemo flicker

[Michael Van Canneyt]

On Tue, 30 Apr 2013, shoKwave wrote:

> Am 30.04.2013 07:25, schrieb Jürgen Hestermann:
>> Maybe someone can just try my example program.
> OK, now I've tested a bit and BeginUpdate/EndUpdate works for me (Win7 x64, 
> FPC and Laz Trunk):
>
> procedure TForm1.Button1Click(Sender: TObject);
> var i:Integer;
> begin
>  Memo1.Clear;
>  for i := 1 to 40 do
>  begin
>    if odd(i) then
> Memo1.Append('\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\')
>    else
> Memo1.Append('+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++');
>  end;
>
>  for i := 1 to 1000 do
>  begin
>    memo1.Lines.BeginUpdate;
>    Memo1.Lines[Memo1.Lines.Count-1] := '#### LAST LINE 
> ---'+IntToStr(i)+'-----------------------------------------------------------';
>    memo1.Lines.EndUpdate;
>    Application.Processmessages;
>  end;
>  Memo1.Lines[memo1.Lines.Count-1] := '#### READY #### ';
> end;
>

It should be
   memo1.Lines.BeginUpdate;
   for i := 1 to 1000 do
     Memo1.Lines.Add('#### LAST LINE  ---'+IntToStr(i)+'-----------------------------------------------------------');
   memo1.Lines.EndUpdate;
   Application.Processmessages;

What you did makes no sense whatsoever. 
The whole point of beginupdate/endupdate is to mark a list of changes, and to prevent the UI from updating while you do the changes.

The use of Add() is easier to understand.

Michael.