JS handler can be added via evaluateJavaScript, and Qt bridge used to provide actual handling via exported QObject

I've considered adding API for C++ event hadlers, but that would require some development effort

It is not allowed to use UI related Qt classes in a different thread. They all must be used in the same thread in which the event loop is executed.
Why do you want to use QWebPage in a different thread?
As far as I know the UI of your application should not block while the web page is loaded.

@maximo the problem is that page`s url is not changing when song data changes. I solved the problem by checking song data using a timer and emiting my own signal.

Solved from https://forum.qt.io/topic/17139/solved-how-to-use-ssl-support-without-manualy-building-qt-libraries/6

added CONFIG += openssl-linked
copied from the QtSdk the (MingW) libeay32.dll and ssleay32.dll in the same folder as the executable

@jelicicm After some analysis I'm to unsure about the detailed working of it.
However QXmlStreamReader can help you in extracting the links which you can probably use in your web crawler implemention as shown in that example.
Also to implement something as simple as searching you can instead resort to QTextStream. Set the html content as byte array to it. The iterate over it, extract the line and check if the particular word exists in it using QString::contains.