Problem with inserting text into QTextEdit

[xorrr]

There is next problem. I need to insert QTextBlock at the beginning of document, which attached with QTextEdit without autoscrolling on this position.

I do next:

QTextCursor cursor = textEdit->textCursor();
cursor.movePosition(QTextCursor::Start);
 
QTextBlockFormat bf;
QTextCharFormat cf;
 
cursor.insertBlock(bf, cf);
cursor.insertText(text);

QTextCursor cursor = textEdit->textCursor();
cursor.movePosition(QTextCursor::Start);

QTextBlockFormat bf;
QTextCharFormat cf;

cursor.insertBlock(bf, cf);
cursor.insertText(text);

To copy to clipboard, switch view to plain text mode 

After, QTextEdit scrolls at the inserted TextBlock.

PS: I did cursor.scrollToAnchor(anchor), but it is very slow.