66 lines
2.1 KiB
JavaScript
66 lines
2.1 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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"use strict";
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this.EXPORTED_SYMBOLS = ["ScrollbarSampler"];
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const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
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Cu.import("resource://gre/modules/Services.jsm");
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Cu.import("resource://gre/modules/XPCOMUtils.jsm");
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var gSystemScrollbarWidth = null;
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this.ScrollbarSampler = {
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getSystemScrollbarWidth: function() {
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if (gSystemScrollbarWidth !== null) {
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return Promise.resolve(gSystemScrollbarWidth);
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}
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return new Promise(resolve => {
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this._sampleSystemScrollbarWidth().then(function(systemScrollbarWidth) {
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gSystemScrollbarWidth = systemScrollbarWidth;
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resolve(gSystemScrollbarWidth);
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});
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});
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},
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resetSystemScrollbarWidth: function() {
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gSystemScrollbarWidth = null;
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},
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_sampleSystemScrollbarWidth: function() {
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let hwin = Services.appShell.hiddenDOMWindow;
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let hdoc = hwin.document.documentElement;
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let iframe = hwin.document.createElementNS("http://www.w3.org/1999/xhtml",
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"html:iframe");
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iframe.setAttribute("srcdoc", '<body style="overflow-y: scroll"></body>');
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hdoc.appendChild(iframe);
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let cwindow = iframe.contentWindow;
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let utils = cwindow.QueryInterface(Ci.nsIInterfaceRequestor)
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.getInterface(Ci.nsIDOMWindowUtils);
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return new Promise(resolve => {
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cwindow.addEventListener("load", function onLoad(aEvent) {
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cwindow.removeEventListener("load", onLoad);
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let sbWidth = {};
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try {
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utils.getScrollbarSize(true, sbWidth, {});
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} catch (e) {
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Cu.reportError("Could not sample scrollbar size: " + e + " -- " +
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e.stack);
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sbWidth.value = 0;
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}
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// Minimum width of 10 so that we have enough padding:
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sbWidth.value = Math.max(sbWidth.value, 10);
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resolve(sbWidth.value);
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iframe.remove();
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});
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});
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}
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};
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Object.freeze(this.ScrollbarSampler);
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