#72 Register Qwt enums as MetaObjects

[Anonymous]

plz register enums of Qwt project with macro Q_ENUM, e.g. QwtSymbols::Styles

Q_ENUM(styles)

to make the enums known to the meta-object system. That is mandatory if you want to use
QVariant with enums of Qwt.

[Uwe Rathmann]

Q_ENUM requires Q_OBJECT or Q_GADGET. Q_OBJECT is often no option as QObject is a heavy class. F.e there are plots having many markers - QwtSymbol being an QObject is no option for them.

Q_GADGET is a different story, but is only available since Qt 5.5.