我们创建一个IDWriteFactory7 CComPtr接口：

CComPtr<IDWriteFactory7>                    _writeFactory;

_hr = DWriteCreateFactory(DWRITE_FACTORY_TYPE_SHARED, __uuidof(_writeFactory), reinterpret_cast<IUnknown**>(&_writeFactory));

创建工厂工作。但如果我们尝试创建IDWriteTextLayout4，则使用以下工厂：

CComPtr<IDWriteTextLayout4> _textLayout;

_writeFactory->CreateTextLayout(
                wtext.c_str(),      // The string to be laid out and formatted.
                wcslen(wtext.c_str()),  // The length of the string.
                _textFormat,  // The text format to apply to the string (contains font information, etc).
                size.width,         // The width of the layout box.
                size.height,        // The height of the layout box.
                &_textLayout  // The IDWriteTextLayout interface pointer.
            );

CreateTextLayout（..）方法不能使用IDWriteTextLayout4，而是需要IdWriteTextLayout。

有人能举个例子吗？