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/* -*- mode: js; indent-tabs-mode: nil; js-indent-level: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
"use strict";
var EXPORTED_SYMBOLS = ["TabUnloader"];
const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
/**
* This module is responsible for detecting low-memory scenarios and unloading
* tabs in response to them.
*/
var TabUnloader = {
/**
* Initialize low-memory detection and tab auto-unloading.
*/
init() {
if (Services.prefs.getBoolPref("browser.tabs.unloadOnLowMemory", true)) {
Services.obs.addObserver(this, "memory-pressure", /* ownsWeak */ true);
}
},
observe(subject, topic, data) {
if (topic == "memory-pressure" && data != "heap-minimize") {
unloadLeastRecentlyUsedTab();
}
},
QueryInterface: ChromeUtils.generateQI([
"nsIObserver",
"nsISupportsWeakReference",
]),
};
function unloadLeastRecentlyUsedTab() {
let bgTabBrowsers = getSortedBackgroundTabBrowsers();
for (let tb of bgTabBrowsers) {
if (tb.browser.discardBrowser(tb.tab)) {
return;
}
}
}
/* Sort tabs in the order we use for unloading, first non-pinned, non-audible
* tabs in LRU order, then non-audible tabs in LRU order, then non-pinned
* audible tabs in LRU order and finally pinned, audible tabs in LRU order. */
function sortTabs(a, b) {
if (a.tab.soundPlaying != b.tab.soundPlaying) {
return a.tab.soundPlaying - b.tab.soundPlaying;
}
if (a.tab.pinned != b.tab.pinned) {
return a.tab.pinned - b.tab.pinned;
}
return a.tab.lastAccessed - b.tab.lastAccessed;
}
function getSortedBackgroundTabBrowsers() {
let bgTabBrowsers = [];
for (let win of Services.wm.getEnumerator("navigator:browser")) {
for (let tab of win.gBrowser.tabs) {
if (!tab.selected && tab.linkedBrowser.isConnected) {
bgTabBrowsers.push({ tab, browser: win.gBrowser });
}
}
}
return bgTabBrowsers.sort(sortTabs);
}
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