Run attached test program SwingComponentToFront.fx (2 files). Take care that the cursor is not over the window! Panel ORANGE is transparent. A Timeline is started and calls ORANGE.toFront.

TO 1.

Console output:

SwingJPanel ancestorAdded ORANGE
SwingJPanel addNotify ORANGE
SwingJPanel ancestorAdded GREEN
SwingJPanel addNotify GREEN
SwingJPanel ancestorAdded BLUE
SwingJPanel addNotify BLUE
toFrontTimeline : fxJPanelOrange.toFront
SwingJPanel ancestorRemoved ORANGE
SwingJPanel removeNotify ORANGE
SwingJPanel ancestorRemoved GREEN
SwingJPanel removeNotify GREEN
SwingJPanel ancestorRemoved BLUE
SwingJPanel removeNotify BLUE
SwingJPanel ancestorAdded GREEN
SwingJPanel addNotify GREEN
SwingJPanel ancestorAdded BLUE
SwingJPanel addNotify BLUE

'ancestorAdded ORANGE' and 'addNotify ORANGE' are missing !

These messages will be printed as soon as the cursor enters the dirty region !

Workaround: set opacity to 0.00001


To 2.

A click on GREEN, BLUE or ORANGE calls toFront and moves it to front, but throws a NullPointerException !

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
  at com.sun.embeddedswing.EmbeddedEventQueue.moveToVisibleAndOnScreen(EmbeddedEventQueue.java:155)
  at com.sun.embeddedswing.EmbeddedEventQueue.beforeDispatch(EmbeddedEventQueue.java:376)
  at com.sun.embeddedswing.EmbeddedEventQueue.access$400(EmbeddedEventQueue.java:74)
  at com.sun.embeddedswing.EmbeddedEventQueue$EventQueueDelegateFactory$2.call(EmbeddedEventQueue.java:728)
  at com.sun.java.swing.SwingUtilities3$EventQueueDelegateFromMap.beforeDispatch(Unknown Source)
  at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
  at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
  at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
  at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
  at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
  at java.awt.EventDispatchThread.run(Unknown Source)