Wrong Drawing of ListBox if it is on a Panel with DoubleBuffered = True

Quanos Service Solutions GmbH

Put a Panel on a Form and put a TELListBox on the Panel.
If the Panel.DoubleBuffered = True ist set, the ListBox doesn't paint correct any more



I would like to attach a file - even a 5,2 kByte PNG-File doesn't work

Quanos Service Solutions GmbH

Also if you put a ListBox on a Form an set DoubleBufferd=True, the Items disappear.

I use XE6

Eugene Balabuev (LMD)

Hi,

This happens because in latest Delphi versions controls has ParentDoubleBuffered property, which is True by default. And so, if you set DoubleBuffered to True on the parent panel, its will be automatically set to True on the child ElListBox.

As a workaround, please reset DoubleBuffered property back to False for the list-box in the OnFormCreate event:

procedure TForm1.FormCreate(Sender: TObject);

begin

  ElListBox1.DoubleBuffered := False;

end;

Quanos Service Solutions GmbH

Thanks. That help for me as a hotfix.

But TELListBox must (!) work correct with DoubleBuffered TRUE.
In older version of ElPack (With D6) it works correct.
With disabled Doubledbuffer, we get flicker-Problem with TElListBox.

And if I use TListBox, this will work with doublebuffer without flickering

Eugene Balabuev (LMD)

Hi,

The bug has been fixed.