remove top old blocks from QTextEdit

Qt.QTextEdit.rmOldBlocks.cpp

QTextBlock block = document()->begin();
while(block.isValid()) {
    if(document()->blockCount() > m_maxlines)
    {
        QTextCursor cursor(block);
        block = block.next();
        cursor.select(QTextCursor::BlockUnderCursor);
        //move forward one character to select the return-char, 
        //in order to avoid the empty line after the selected text is removed.
        cursor.movePosition(QTextCursor::NextCharacter,QTextCursor::KeepAnchor);
        cursor.removeSelectedText();
    }else{
        break;
    }
}

cursor.removeSelectedText();

似乎会将text删除，但是对于空行而言，selected text是“”，remove不了，如何解决这个问题？

将选择光标移动到下一个字符QTextCursor::NextCharacter，即'\n'后，将换行符一并删除，可以保证blockCount减小，从而删除正确的行数，还能避免remove后留下空行。