In Mac OSX windows drop shadows onto the desktop and other app windows, and so does a JavaFX app by default, but the shadow changes if you change the StageStyle, as follows:

StageStyle.DECORATED – JavaFX works as it should by dropping a normal mac window shadow.
StageStyle.UNDECORATED – JavaFX app window works but shadow is more more vague than normal.
StageStyle.TRANSPARENT – the JavaFX app window no longer drops any shadow.

I need to create an undecorated window with rounded corners. To do that, I need to select StageStyle.TRANSPARENT and add a clip to the contents. Everything renders correctly except now I loose the Mac OSX window drop shadow.