The following question is about RichTexFX. For standard JavaFX components, I've never had this issue before.
In my application, I am adding text content to the end of a GenericStyledArea (actually a subclass of it, but that should have no impact on the behaviour I am observing). Every time new content has been added to the end of the document, I scroll to the bottom so the new content is always in view. I use the following code to scroll to bottom (actually written in Kotlin, but I have translated it to Java below):
showParagraphAtTop(document.getParagraphs().size() - 1)
This almost always works. However, in some cases the screen will not show the newly added element. I have come to the conclusion that by the time showParagraphAtTop is called, some internal state in richtextfx has not been updated. This is because I added a button that I can click on to call the code above, and if I click it after the scroll failed, it scrolls to the bottom as expected.
I have tried various ways to work around this, but the only solution that works reliably is to do the following:
FxTimer.runLater(Duration.ofMillis(10), () -> showParagraphAtTop(getDocument().getParagraphs().size() - 1));
In other words, I force a short delay before actually scrolling the screen.
Even though the above works, it's incredibly unsatisfactory, and there should be some way to do this the right way. However, I have been unable to figure it out.
I saw another question (Autoscroll JavaFX TextFlow) which suggested the use of layout() prior to scrolling. This does not remove the problem, although it does appear to make it less common.