Qt 5.9 introduces many new features and improvements as well as bugfixes
over the 5.8.x series. For more details, refer to the online documentation
included in this distribution. The documentation is also available online:

http://doc.qt.io/qt-5/index.html

The Qt version 5.9 series is binary compatible with the 5.8.x series.
Applications compiled for 5.8 will continue to run with 5.9.

There were no changes in this module since the 5.8.x series.