chore: extract graphics init to function

src/hello.cpp

@@ -82,6 +82,38 @@ float getTime()
 #include <cmath>
 #include "astro/twoBodyMethods.hpp"
 
+// Initialize GLFW, OpenGL and GLEW, open a window and make it the current context.
+// Returns 0 for success, and -1 for any failure.
+// Failures are printed to STDERR.
+int initGraphics(GLFWwindow** window)
+{
+    // Set up GLFW, OpenGL and GLEW.
+    if (!glfwInit())
+    {
+        std::cerr << "Failed to initialize GLFW" << std::endl;
+        return -1;
+    }
+
+    *window = glfwCreateWindow(640, 480, "Hello Astro", NULL, NULL);
+    if (!window)
+    {
+        glfwTerminate();
+        std::cerr << "Failed to open window with GLFW" << std::endl;
+        return -1;
+    }
+
+    glfwMakeContextCurrent(*window);
+
+    glewExperimental = GL_TRUE;
+    if (glewInit() != GLEW_OK)
+    {
+        std::cerr << "Failed to initialize GLEW" << std::endl;
+        return -1;
+    }
+
+    return 0;
+}
+
 int main()
 {
     // Calculate period of ISS orbit around the Earth
@@ -94,26 +126,10 @@ int main()
     glm::vec3 v(0.0, 1.0, 2.0);
     std::cout << "(" << v.x << ", " << v.y << ", " << v.z << ")" << std::endl;
 
-    // Set up GLFW, OpenGL and GLEW.
-    if (!glfwInit())
+    GLFWwindow* window = nullptr;
+    if (initGraphics(&window) != 0)
         return -1;
 
-    GLFWwindow* window = glfwCreateWindow(640, 480, "Hello Astro", NULL, NULL);
-    if (!window)
-    {
-        glfwTerminate();
-        return -1;
-    }
-
-    glfwMakeContextCurrent(window);
-
-    glewExperimental = GL_TRUE;
-    if (glewInit() != GLEW_OK)
-    {
-        std::cerr << "Failed to initialize GLEW" << std::endl;
-        return -1;
-    }
-
     // VAO, VBO
     float vertices[] =
     {