I use LIBS flag to link qwt library to my project. So in .pro of my project i have
LIBS += -L/home/Desktop/qwt-6.0.1/lib -lqwt
But anyway Qt does not recognize qwt classes. What i'm missing ??
I think you forgot to include the headers.
Try to add the following
INCLUDE += /home/Desktop/qwt-6.0.1/include