Just to close the loop in case anyone else runs into this, the main problem was that I hadn't called gtkGlArea's make_current() function. This is necessary to make the OpenGL rendering context available for subsequent commands.
Once I did that, both the Epoxy version number and the original glewInit() functions work correctly. I had incorrectly thought that rendering context was automatically made current either after instantiating the widget, or at least in it's on_realize() signal handler. On Sun, 2021-04-11 at 12:41 +0000, JLM via gtkmm-list wrote: > So I found this example: > > https://github.com/GNOME/gtkmm/blob/master/demos/gtk-demo/example_glarea.cc > > And it has #include <epoxy/gl.h> , and I thought, "what is that?" > > So I found this: > > https://github.com/anholt/libepoxy > > And, gee, it just works! > > I'm not sure if this is enough, becase epoxy_gl_version() returns 0, > but the glArea->get_required_version() returns 4.5. I'll pretend it > doesn't matter for now and bug someone (else?) later if I'm again at > my > wit's end. > > On Sun, 2021-04-11 at 01:52 +0000, JLM via gtkmm-list wrote: > > I am trying to make use of OpenGL 4.5 in a gtkGlArea. The code > > below > > works. However, I have the OpenGL Programming Guide Ninth Edition, > > and > > it uses this instead of glClearColor: > > > > static const float black[] = { 0.0, 0.0, 0.0, 0.0 }; > > glClearBufferfv(GL_COLOR, 0, black); > > > > When I try to use that, the compile doesn't find it: > > > > gtkgl.cpp:32:5: error: 'glClearBufferfv' was not declared in this > > scope; did you mean 'glReadBuffer'? > > 32 | glClearBufferfv(GL_COLOR, 0, black); > > > > I also tried #include <GL/glext.h> but that didn't help. > > > > So then I thought maybe I need to make use of GLEW. When I #include > > <GL/glew.h>, that compiles at least. But, then I can't run GLEW's > > setup: > > > > GLenum glewError = glewInit(); > > if(glewError != GLEW_OK) > > { > > std::cerr << "Error: " << glewGetErrorString(glewError) << > > std::endl; > > } > > > > When I run, it always says: > > > > Error: Missing GL version > > > > So then I found the gtkGlArea method, set_required_version, and set > > it: > > > > gl > > Area->set_required_version(4, 5); > > > > But that still didn't help. So then I thought maybe the GLEW init > > needs > > to be in the on_realize() section, as I saw that this is where you > > put > > OpenGL init stuff, but that still didn't work. > > > > So, what do I need to #include? Should I make use of GLEW, or does > > GTK(MM) do everything necessary to get OpenGL already? Are there > > any > > tutorials or examples? Most everything I find is for OpenGL 3.3, > > but I > > don't know how to align that with the book I've got. > > > > Thanks for any help you can provide. > > > > > > #include <gtkmm.h> > > #include <iostream> > > #include <GL/gl.h> > > #include <GL/glu.h> > > > > Gtk::Window* pDialog = nullptr; > > > > static > > void on_button_clicked() > > { > > if(pDialog) > > pDialog->hide(); //hide() will cause main::run() to end. > > } > > > > bool glRender(const Glib::RefPtr<Gdk::GLContext>&) > > { > > glClearColor(1.0f, 0.3f, 0.3f, 1.0f); > > glClear(GL_COLOR_BUFFER_BIT); > > return true; > > } > > > > int main (int argc, char **argv) > > { > > auto app = Gtk::App > > lication::create(argc, argv, "org.test"); > > > > //Load the GtkBuilder file and instantiate its widgets: > > auto refBuilder = Gtk::Builder::create(); > > try > > { > > refBuilder->add_from_file("glarea.glade"); > > } > > catch(const Glib::FileError& ex) > > { > > std::cerr << "FileError: " << ex.what() << std::endl; > > return 1; > > } > > catch(const Glib::MarkupError& ex) > > { > > std::cerr << "MarkupError: " << ex.what() << std::endl; > > return 1; > > } > > catch(const Gtk::BuilderError& ex) > > { > > std::cerr << "BuilderError: " << ex.what() << std::endl; > > return 1; > > } > > > > //Get the GtkBuilder-instantiated Dialog: > > refBuilder->get_widget("Window", pDialog); > > if(pDialog) > > { > > //Get the GtkBuilder-instantiated Button, and connect a > > signal > > handler: > > Gtk::MenuItem* pButton = nullptr; > > refBuilder->get_widget("quitMenuItem", pButton); > > if(pButton) > > { > > pButton->signa > > l_activate().connect( sigc::ptr_fun(on_button_clicked) ); > > } > > > > Gtk::GLArea* glArea = nullptr; > > refBuilder->get_widget("glarea", glArea); > > if(glArea) > > { > > glArea->signal_render().connect(sigc::ptr_fun(glRender) > > ); > > } > > app->run(*pDialog); > > } > > > > delete pDialog; > > > > return 0; > > } > > > > _______________________________________________ > > gtkmm-list mailing list > > gtkmm-list@gnome.org > > https://mail.gnome.org/mailman/listinfo/gtkmm-list > > > _______________________________________________ > gtkmm-list mailing list > gtkmm-list@gnome.org > https://mail.gnome.org/mailman/listinfo/gtkmm-list
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