Actually render to GL (#23)

Author: ktf

DebugGUI/src/DebugGUI.cxx

@@ -77,6 +77,7 @@ bool pollGUI(void* context, std::function<void(void)> guiCallback)
     guiCallback();
   }
   ImGui::Render();
+  ImGui_ImplGlfwGL3_RenderDrawLists(ImGui::GetDrawData());
   glfwSwapBuffers(window);
   return true;
 }

DebugGUI/src/imgui_impl_glfw_gl3.h

@@ -7,10 +7,12 @@
 // https://github.com/ocornut/imgui
 
 struct GLFWwindow;
+struct ImDrawData;
 
 IMGUI_API bool        ImGui_ImplGlfwGL3_Init(GLFWwindow* window, bool install_callbacks);
 IMGUI_API void        ImGui_ImplGlfwGL3_Shutdown();
 IMGUI_API void        ImGui_ImplGlfwGL3_NewFrame();
+IMGUI_API void        ImGui_ImplGlfwGL3_RenderDrawLists(ImDrawData* draw_data);
 
 // Use if you want to reset your rendering device without losing ImGui state.
 IMGUI_API void        ImGui_ImplGlfwGL3_InvalidateDeviceObjects();