When a layout Pane is autosized, it's setWidth/setHeight gets called, which in turn calls Region#widthChanged/heightChanged, causing requestLayout to be called on the Pane. This often invalidates many of the computations done when querying size hints before autosizing the layout.

This probably also applies to any layout. The typical scenario is:

1) get size hints - invoke (partial) computation of the layout
2) resize/position - requestLayout called on the children
3) layout child - the computations done in #1 are done again