Print a WebPage that isn't shown

[AlexxanderX]

Hello. How can I print a page that isn't showed on a window/widget?

QPainter painter(printer);
    m_webView->page()->setViewportSize(m_pageToPrint->mainFrame()->contentsSize());
    painter.scale(scale, scale);
    m_pageToPrint->mainFrame()->render(&painter);

QPainter painter(printer);
    m_webView->page()->setViewportSize(m_pageToPrint->mainFrame()->contentsSize());
    painter.scale(scale, scale);
    m_pageToPrint->mainFrame()->render(&painter);

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This is the code used( now is converted from m_webView to m_pageToPrint) to print the page from webView, which is showed, but the code for m_pageToPrint which isn't showed, only loaded with the HTML to be printed? The result of the above code is a white page in the PrinterPreviewer.
This is the code to load the html and after to call the previewer:

m_pageToPrint->mainFrame()->setHtml(finalHTML);
m_printPreviewDialog->exec();

m_pageToPrint->mainFrame()->setHtml(finalHTML);
m_printPreviewDialog->exec();

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finalHTML is a valid html code.