The TSF tour ends here, with a brief discussion of UI Elements in Vista
If your text service wishes to be available in full-screen applications like games, it must implement ITfUIElement, and call the ITfUIElementMgr whenever the text service wants to display some UI. (See the discussion of UILess mode in MSDN.)
Passed to ITfUIElementMgr::BeginUIElement
QI from ITfUIElement
Text services that implement ITfUIElement should also register in the GUID_TFCAT_TIPCAP_UIELEMENTENABLED category, as well.
Unfortunately, as of this date, I do not know of any sample text service that implements ITfUIElement.