Hello Dennis,
I was able to reproduce the situation. The error can occur when the layout of the Outline Box is invalidated again just after the end of the preceding layout update and before the delivery of a signal to the OnUpdate slot method. The signal is posted at the end of the layout update and it is thus deferred. The mentioned invalidation of the Outline Box layout can be provoked when e.g. a new view is added to the Outline Box or an already existing view changes its size.
Since the situation depends on the timing behaviour of the application it is difficult to deduce the exact cause in your application case. In fact I had to try different tricks to provoke it. For the next version we will rework the Outline Box to explicitly postpone the OnUpdate signal when in the meantime the layout has been invalidated again. For the actual version I would suggest following workaround:
From your description I have understood that actually the Outline Box is connected via its property OnUpdate to a slot method updateScrollbars. Then:
1. Add a new slot method to the component. Name it e.g. preUpdateScrollbars.
2. Change the property OnUpdate of the Outline Box to refer the just added slot method preUpdateScrollbars.
3. Implement the new slot method with following code:
postsignal updateScrollbars;
The additional slot method causes the signal to be postponed through which the Outline Box will have enough time to complete the pending layout update.
Let me know whether the workaround does solve the issue.
Best regards
Paul Banach