From 03f0c9af078adfbd6e05e9206ecdcc153ba08a1f Mon Sep 17 00:00:00 2001
From: Brendan Hansen <brendan.f.hansen@gmail.com>
Date: Tue, 13 Oct 2020 17:08:04 -0500
Subject: [PATCH] added delta time calculation

---
 src/sim.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/sim.c b/src/sim.c
index a5dc708..1a35ade 100644
--- a/src/sim.c
+++ b/src/sim.c
@@ -62,20 +62,29 @@ void deinit_opengl() {
 	glfwTerminate();
 }
 
-void update() {
+// NOTE: dt is expected to be in units of "per second".
+void update(double dt) {
 }
 
 void draw() {
-	glClearColor(1.0, 0.0, 1.0, 1.0);
+	glClearColor(0.1, 0.1, 0.1, 1.0);
 	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 	glfwSwapBuffers(window);
 }
 
 void loop() {
+	double last_time = glfwGetTime();
+	double curr_time = last_time;
+	double delta;
+
 	while (!glfwWindowShouldClose(window)) {
 		glfwPollEvents();
 
-		update();
+		curr_time = glfwGetTime();
+		delta = curr_time - last_time;
+		last_time = curr_time;
+
+		update(delta);
 		draw();
 	}
 }
-- 
2.25.1