forked from mirrors/gecko-dev
6feaa5a9c3
MozReview-Commit-ID: BYTDdLU2HoM --HG-- extra : rebase_source : 1e31ff288280d09ae226cdc698331263ba969205
60 lines
1.8 KiB
JavaScript
60 lines
1.8 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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var EXPORTED_SYMBOLS = ["ScrollbarSampler"];
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ChromeUtils.import("resource://gre/modules/Services.jsm");
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var gSystemScrollbarWidth = null;
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var ScrollbarSampler = {
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getSystemScrollbarWidth() {
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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() {
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gSystemScrollbarWidth = null;
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},
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_sampleSystemScrollbarWidth() {
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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.windowUtils;
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return new Promise(resolve => {
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cwindow.addEventListener("load", function(aEvent) {
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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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}, {once: true});
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});
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}
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};
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Object.freeze(this.ScrollbarSampler);
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