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