怎么确定editor已经翻到文档结尾和文档开始

如何确定editor已经翻到文档结尾和文档开始
如何确定editor已经翻到文档结尾和文档开始

[解决办法]
则和要通过获取行来计算，这是我曾经在RichTextEditor中实现其模拟Label显示时的滚动效果。。希望可以有所帮助。。。

C/C++ code

TTmLineInfo lineInfo;        TTmPosInfo2 posInfo;        TInt totalLineNumber = iAnsLabel->TextLayout()->GetLineNumber(iAnsLabel->RichText()->DocumentLength());                //获取当前光标在文本中的行数        TInt currentLineNumber;        TTmDocPosSpec docPos(iAnsLabel->CursorPos(),                TTmDocPosSpec::ELeftToRight);        iAnsLabel->TextView()->FindDocPosL(docPos, posInfo, &lineInfo);        currentLineNumber=lineInfo.iLineNumber;        const TRect viewRect = iAnsLabel->TextView()->ViewRect(); // visiable rect        //获取当前屏幕中最下面行在文本中的行数(brLineNumber)及右底端光标的坐标(brPos)        TInt brLineNumber/*, brPos*/;        iAnsLabel->TextLayout()->FindXyPos(viewRect.iBr, posInfo, &lineInfo);        brLineNumber=lineInfo.iLineNumber;、        //获取当前屏幕中最上面行在文本中的行数(tlLineNumber)及左顶端光标的坐标(tlPos)        TInt tlLineNumber/*, tlPos*/;        iAnsLabel->TextLayout()->FindXyPos(viewRect.iTl, posInfo, &lineInfo);        tlLineNumber=lineInfo.iLineNumber;        //tlPos=posInfo.iDocPos.iPos;        TInt viewRectLineNumber=brLineNumber-tlLineNumber;        if (aKeyEvent.iCode == EKeyUpArrow)            {            if (currentLineNumber == brLineNumber)                {                //iAnsLabel->SetCursorPosL(tlPos, EFalse);                for (TInt i=0; i<viewRectLineNumber; i++)                    iAnsLabel->MoveCursorL(TCursorPosition::EFLineUp, EFalse);                }            }        if (aKeyEvent.iCode == EKeyDownArrow)            {            if (currentLineNumber == tlLineNumber)                {                //iAnsLabel->SetCursorPosL(brPos, EFalse);                for (TInt i=0; i<viewRectLineNumber; i++)                    iAnsLabel->MoveCursorL(TCursorPosition::EFLineDown, EFalse);                }            //if(iAnsLabel->CursorPos() == iAnsLabel->RichText()->DocumentLength())            if (currentLineNumber == totalLineNumber)                {                this->SwitchFocus();                return EKeyWasConsumed;                }            }        }
[解决办法]
TextLength和PosRangeInBand结合使用