vaadin combobox suggestion popup displays outside of vaadin window in lifer

I have a vaadin-liferay portlet. I am using vaadin Window component which is having vertical scroll as it has more content inside. A combobox is added inside the window. But when the combobox suggestion popup opened its position is changed according to the browser scroll not according to vaadin window scroll. Please help

That’s a “feature” of how the ComboBox is implemented - the popup is actually an overlay, which has a completely different root element than the edit field part (see DOM in e.g. Chrome inspector). Using overlays like that has some benefits and downsides, one downside being that kind of scroll behavior. If you don’t need any ComboBox specific functionality, you might consider using a NativeSelect instead.