To use Qt Help classes, add this directive into the C++ files:
To link against the Qt Help module, add this line to the project file:
QT += help
The classes and tools supplied with Qt to enable developers to include online help and documentation in their applications are described in more detail in The Qt Help Framework.
These are links to the API reference material:
Qt Help is available under commercial licenses from The Qt Company. In addition, it is available under free software licenses. Since Qt 5.4, these free software licenses are GNU Lesser General Public License, version 3, or the GNU General Public License, version 2. See Qt Licensing for further details.