Qwt 6: moving to size_t (unsigned) integer type for sizes and indexes was unfortunate

[Uwe]

Your observation is not 100% correct: size_t is inherited from Qwt5 ( AFAIR even earlier, see the history of QwtData ) invented at a time when Qt containers where also using unsigned. All what has been done in Qwt6 is to fix the inconsistent API of a wrapping method.
When Qt development came up with a new template library it was not possible to simply adjust Qwt - remember Qwt5 supports Qt3/Qt4.

But I agree, that using integers has become standard since Qt4 and it could be changed in Qwt as well.

Uwe