Qt WebChannel – bridging the gap between C /QML and the web

Hybrid applications, which mix a UI built with Qt Widgets or Qt Quick with embedded HTML websites, are very popular. In particular, something like an HTML 5 app framework is often requested by customers. Qt WebKit makes it trivial to embed HTML content in any graphical application. But how does one bridge the gap between C /QML on one side, and HTML/JavaScript on the other side?
Source: Ziobudda.net