From df4d195ec7135c76f8f5de54c3939d2e74e80d4a Mon Sep 17 00:00:00 2001
From: Stefan Malzner <stefan@adlk.io>
Date: Sat, 24 Nov 2018 20:20:31 +0100
Subject: Delay app based on featureAPI settings

---
 src/helpers/visibility-helper.js | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 src/helpers/visibility-helper.js

(limited to 'src/helpers/visibility-helper.js')

diff --git a/src/helpers/visibility-helper.js b/src/helpers/visibility-helper.js
new file mode 100644
index 000000000..8456c4ecf
--- /dev/null
+++ b/src/helpers/visibility-helper.js
@@ -0,0 +1,27 @@
+export function onVisibilityChange(cb) {
+  let isVisible = true;
+
+  if (!cb) {
+    throw new Error('no callback given');
+  }
+
+  function focused() {
+    if (!isVisible) {
+      cb(isVisible = true);
+    }
+  }
+
+  function unfocused() {
+    if (isVisible) {
+      cb(isVisible = false);
+    }
+  }
+
+  document.addEventListener('visibilitychange', () => { (document.hidden ? unfocused : focused)(); });
+
+  window.onpageshow = focused;
+  window.onfocus = focused;
+
+  window.onpagehid = unfocused;
+  window.onblur = unfocused;
+}
-- 
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