try to find GTK (and glib) and GTKGLArea
GTK_INCLUDE_DIR - Directories to include to use GTK GTK_LIBRARIES - Files to link against to use GTK GTK_FOUND - GTK was found GTK_GL_FOUND - GTK's GL features were found
© 2000–2016 Kitware, Inc.
© 2000–2011 Insight Software Consortium
Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.5/module/FindGTK.html