Replace text

To replace text of TextBlock by my text i use:

cursor = QTextCursor(block);
сursor.movePosition(QTextCursor::EndOfBlock, QTextCursor::KeepAnchor);
cursor.insertText(newText);

But is real slowly . Any ideas?

QString::replase() doesnt help?

i work with QTextDocument
so i think QString::replace is not real useable
hard to find text to replace if many equal lines