On Windows 8, when using Chinese input method on TextField or TextArea, the candidate window is always placed at the bottom of the screen. It should be just below the input caret.
Attached screen shots of Notepad (win8-notepad-zh_TW-im-candidates.png) and TextField (win8-textfield-zh_TW-im-candidates.png) to show the difference.

It seems only the horizontal candidate window is affected. The IMEs with vertical candidate window is fine, including ja IME and zh_TW Phonetic IME.

Swing JTextField and JTextArea have the same behavior as JavaFX.