Text Cursor disappears from QTextEdit when QTextFrameFormat is changed.

I am having trouble with a QTextEdit: When I change the QTextFrameFormat, of the underlying QTextDocument's rootFrame, the visible cursor disappears. But it only happens if the QTextEdit is empty, and the cursor only reappears if I input text, or resize the window.

Here is what I am doing:

Code:

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QTextFrameFormat frameFormat = textEdit->document()->rootFrame()->frameFormat();
textEdit->document()->rootFrame()->setFrameFormat(frameFormat);

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Of course in my code, I would make some changes to the QTextFrameFormat, but that is not even necessary for the problem to happen.
Any clues on what is happening, and how to solve it?

Thanks in advance,

Luca Rood