add OpenGL bootstrapping code

src/io/window.c

@@ -2,9 +2,15 @@
 // Licensed under the MIT Licence. See LICENSE for details
 #include "window.h"
 
+// include before GLFW
+#define GLAD_GL_IMPLEMENTATION
+#include <glad/gl.h>
+
+// include system libraries
 #include <GLFW/glfw3.h>
 #include <assert.h>
 #include <stdlib.h>
+
 #include "input.h"
 
 // macros for ease of access
@@ -19,18 +25,19 @@ int window_init(void) {
 	glfwWindowHint(GLFW_RESIZABLE, GLFW_TRUE);
 	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
 	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
-	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); // TODO: read about opengl profiles
+	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
 	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE);
 	win = glfwCreateWindow(WIN_DEFAULT_WIDTH, WIN_DEFAULT_HEIGHT, WIN_NAME, NULL, NULL);
 	if (!win) return 1;
 
-	// make the current window the current context
-	glfwMakeContextCurrent(win);
-
 	// configure callbacks
 	glfwSetKeyCallback(win, key_callback);
 	glfwSwapInterval(1); // wait 1 screen update for a redraw a.k.a. "vsync". (not really applicable in this case but eh)
 
+	// setup OpenGL
+	glfwMakeContextCurrent(win);
+	if (!gladLoadGL(glfwGetProcAddress)) return 1;
+
 	return 0;
 }
 
@@ -39,6 +46,9 @@ void window_loop(void) {
 
 	while (!glfwWindowShouldClose(win)) {
 		glfwWaitEvents(); // wait till an update has been given
+		glClearColor(0.1F, 0.1F, 0.1F, 1.0F);
+		glClear(GL_COLOR_BUFFER_BIT);
+		glfwSwapBuffers(win);
 	}
 
 	glfwDestroyWindow(win);