From bc57e7c2caf32a967ae7dcd4d1769c96acb51a77 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Matt=C3=A9o=20Delabre?= <spam@delab.re>
Date: Mon, 4 May 2020 18:37:33 +0200
Subject: [PATCH] Stop simulation when page is hidden

---
 index.mjs | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/index.mjs b/index.mjs
index 4baf758..882b24e 100644
--- a/index.mjs
+++ b/index.mjs
@@ -45,6 +45,7 @@ for (let i = 0; i < 300; ++i)
     });
 }
 
+let paused = false;
 let lastTime = null;
 
 const loop = time =>
@@ -60,7 +61,34 @@ const loop = time =>
     boids.update(activeBoids, params, delta);
     draw.fill(activeBoids, params, boidsCtx, width, height, center);
 
+    if (!paused)
+    {
+        requestAnimationFrame(loop);
+    }
+};
+
+const start = () =>
+{
+    lastTime = null;
+    paused = false;
     requestAnimationFrame(loop);
 };
 
-requestAnimationFrame(loop);
+const pause = () =>
+{
+    paused = true;
+};
+
+document.onvisibilitychange = () =>
+{
+    if (document.visibilityState === 'visible')
+    {
+        start();
+    }
+    else
+    {
+        pause();
+    }
+};
+
+start();