Just stumbled on this stripping out modules I didn't need in Introjucer and forgot to remove OpenGl....
The Introjucer allows you to leave the juce_opengl module in a project without warning that it seems to be dependent on juce_gui_extra.
Is it dependent on that module? That's odd, because I can't see anywhere in the GL component where it includes any of the code from juce_gui_extras?