ImmGetCompositionString (Windows CE 5.0)

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This function retrieves information about the composition string.

LONG ImmGetCompositionString(  HIMChIMC,  DWORDdwIndex,  LPVOIDlpBuf,  DWORD dwBufLen);


  • hIMC
    [in] Handle to the input context. In Windows CE 2.10 and later, if hIMC is NULL, then the length of the composition string, dwBufLen, is returned for the current active context.
  • dwIndex
    [in] Index of the information to retrieve. This parameter can be one of the values specified in IME Composition String Values. For each value except GCS_CURSORPOS and GCS_DELTASTART, the function copies the requested information to the specified buffer. The function returns the cursor and delta position values in the low 16-bits of the return value.
  • lpBuf
    [out] Long pointer to the buffer that receives the requested information.
  • dwBufLen
    [in] Size of the buffer, in bytes. If zero, the ImmGetCompositionString function returns the buffer size needed for the complete information.

Return Values

The number of bytes copied to the destination buffer or, if dwBufLen is zero, the buffer size, in bytes, needed to receive all of the requested information indicates success. IMM_ERROR_NODATA indicates that the composition data is not ready in the input context. IMM_ERROR_GENERAL indicates that a general error was detected by IME.


An application calls this function in response to the WM_IME_COMPOSITION or WM_IME_STARTCOMPOSITION message. The IMM removes the information when an application calls the ImmReleaseContext function.

Code Example

The following code example demonstrates how to use ImmGetCompositionString.

Note   To make the following code example easier to read, security checking and error handling are not included. This code example should not be used in a release configuration unless it has been modified to include them.

BOOL GetCompositionString( HWND hWnd, LPTSTR *pszCompStr, UINT *cchCompStr )

    DWORD dwBufLen = NULL;

    HIMC hImc = ImmGetContext(hWnd);

    if (!hImc)
        DEBUGMSG(1, (_T("Failed to get handle to current input context.\r\n")));
        return FALSE;

    // Determine how much space is required to store the composition string.
    if ( (dwBufLen = ImmGetCompositionString( hImc, GCS_COMPSTR, NULL, 0l)) < 0 )
        DEBUGMSG(1, (_T("No composition string.\r\n")));
        return FALSE;
    if ( *cchCompStr < (dwBufLen/sizeof(TCHAR)) + 1 )
        DEBUGMSG(1, (_T("pszCompStr needs to be at least %i characters large.\r\n"), 
                 (dwBufLen/sizeof(TCHAR)) + 1));
        *cchCompStr = (dwBufLen/sizeof(TCHAR)) + 1;
        return FALSE;

    ImmGetCompositionString(hImc, GCS_COMPSTR, *pszCompStr, dwBufLen );
    (*pszCompStr)[dwBufLen] = NULL;

    return TRUE;


OS Versions: Windows CE .NET 4.0 and later.
Header: Imm.h.
Link Library: Coreimm.lib.

See Also

ImmReleaseContext | WM_IME_COMPOSITION | WM_IME_STARTCOMPOSITION | IME Composition String Values

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