This is Qt 5 port of Qwt library version 5.  The Qwt library contains
GUI Components and utility classes which are primarily useful for
programs with a technical background.  Beside a 2D plot widget it
provides scales, sliders, dials, compasses, thermometers, wheels
and knobs to control or display values, arrays, or ranges of type
double.

See also: https://github.com/SciDAVis/qwt5-qt5