gradients.pro Example File
painting/gradients/gradients.pro
  SOURCES += main.cpp gradients.cpp
  HEADERS += gradients.h
  SHARED_FOLDER = ../shared
  include($$SHARED_FOLDER/shared.pri)
  RESOURCES += gradients.qrc
  qtHaveModule(opengl) {
          DEFINES += QT_OPENGL_SUPPORT
          QT += opengl
  }
  QT += widgets
  # install
  target.path = $$[QT_INSTALL_EXAMPLES]/widgets/painting/gradients
  INSTALLS += target