When I have some content in my ScrollPane and do the following:

scrollPane.setPrefWidth(ScrollPane.USE_COMPUTED_SIZE);

I can assume that the content size will be used to set the scrollPane width.

However it doesn't work that way. Look at the attached code. It has two scrollPanes with identical content. First scrollPane has prefWidth set to USE_COMPUTED_SIZE, second has it set to 300. See the resulting screenshot.