It is common on macOS to see windows which are slightly translucent and allow the windows behind them to show through in a blurred way. Windows is starting to embrace similar effects with the Mica and Acrylic materials. JavaFX should support these backdrop effects.

Only the OS can draw these effects correctly since they require real-time access to the contents of the desktop and windows belonging to other applications. Implementing this would require asking the OS to draw the backdrop effect so JavaFX can alpha-composite its content on top. This is similar to the old StageStyle.UNIFIED behavior.