Fixed drawing problem when using scrollbars or mouse wheel

Implemented checkbuttons

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@57 8e941d3f-bd1b-0410-a28a-d453659cc2b4

components/virtualtreeview/demos/mininal/Main.pas

@@ -59,7 +59,7 @@ procedure TMainForm.FormCreate(Sender: TObject);
 
 begin
   {$ifdef DEBUG}
-  Logger.ActiveClasses:=[lcScroll];
+  Logger.ActiveClasses:=[];//[lcScroll,lcPaint];
   Logger.Channels.Add(TIPCChannel.Create);
   Logger.Clear;
   Logger.MaxStackCount:=10;