Text Service Framework(TSF) [Application]窗体输入如何实现？

Question

我使用ITfContextOwnerCompositionSink来CreateContext

我希望能够获取输入法上屏的字符，但使用如下代码却什么也获取不到

HRESULT __stdcall TfContextOwnerCompositionSink::OnEndComposition(ITfCompositionView* pComposition)

{

    SendMessage(hwnd, WM_IME_ENDCOMPOSITION, 0, 0);

    ITfRange* range;

    pComposition->GetRange(&range);

    WCHAR* text = new WCHAR[128];

    ULONG pcch;

    range->GetText(cookie, 0, text, 128, &pcch);

    for (int i = 0; i < pcch; i++) {

        WCHAR _char = text[i];

        SendMessage(hwnd, WM_IME_CHAR, _char, 0);

    }

    return S_OK;

}

同时输入时未上屏带下划线部分的字串如何获取