These are IMM function that can be called from a UI window.
ImmGetCompositionWindow
ImmSetCompositionWindow
ImmGetCandidateWindow
ImmSetCandidateWindow
ImmGetCompositionString
ImmSetCompositionString
ImmGetCompositionFont
ImmSetCompositionFont
ImmGetNumCandidateList
ImmGetCandidateList
ImmGetGuideLine
ImmGetConversionStatus
ImmGetConversionList
ImmGetOpenStatus
ImmSetConversionStatus
ImmSetOpenStatus
ImmNotifyIME
ImmCreateSoftKeyboard
ImmDestroySoftKeyboard
ImmShowSoftKeyboard