@nour.m if you mean here: http://freetexthost.com/l5wzgtntzb than no, you did not make the changes @aha_1980 told you to do SOURCES += main.cpp mainwindow.cpp my_polyhedron.cpp myqglwidget.cpp HEADERS += mainwindow.h My_CGAL_Config.h My_Face_base.h My_Halfedge_base.h my_polyhedron.h My_Vertex_base.h myqglwidget.h still mising \ at the end of the line also you are adding the widgets module twice. I'm not sure in what that will result, but you should remove one QT += core gui QT += widgets //remove me DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x000000 greaterThan(QT_MAJOR_VERSION, 4): QT += widgets