| // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| function busyLoop(millis) { |
| for (var d = Date.now(); Date.now() - d < millis; ) { } |
| } |
| |
| function visible() { |
| if ("webkitVisibilityState" in document |
| && document.webkitVisibilityState == "hidden") |
| return false; |
| if ("mozVisibilityState" in document |
| && document.mozVisibilityState == "hidden") |
| return false; |
| if ("msVisibilityState" in document |
| && document.msVisibilityState == "hidden") |
| return false; |
| return true; |
| } |
| |
| var timerId = 0; |
| function loop() { |
| timerId = 0; |
| if (!visible()) |
| return; |
| busyLoop(250); |
| timerId = window.setTimeout(loop, 50); |
| } |
| |
| function handler() { |
| if (visible() && !timerId) |
| timerId = window.setTimeout(loop, 50); |
| } |
| |
| document.addEventListener("webkitvisibilitychange", handler, false); |
| document.addEventListener("mozvisibilitychange", handler, false); |
| document.addEventListener("msvisibilitychange", handler, false); |
| |
| loop(); |