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/* 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";
this.EXPORTED_SYMBOLS = ["ScrollbarSampler"];
const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
Cu.import("resource://gre/modules/Services.jsm");
Cu.import("resource://gre/modules/XPCOMUtils.jsm");
var gSystemScrollbarWidth = null;
this.ScrollbarSampler = {
getSystemScrollbarWidth: function() {
if (gSystemScrollbarWidth !== null) {
return Promise.resolve(gSystemScrollbarWidth);
}
return new Promise(resolve => {
this._sampleSystemScrollbarWidth().then(function(systemScrollbarWidth) {
gSystemScrollbarWidth = systemScrollbarWidth;
resolve(gSystemScrollbarWidth);
});
});
},
resetSystemScrollbarWidth: function() {
gSystemScrollbarWidth = null;
},
_sampleSystemScrollbarWidth: function() {
let hwin = Services.appShell.hiddenDOMWindow;
let hdoc = hwin.document.documentElement;
let iframe = hwin.document.createElementNS("http://www.w3.org/1999/xhtml",
"html:iframe");
iframe.setAttribute("srcdoc", '<body style="overflow-y: scroll"></body>');
hdoc.appendChild(iframe);
let cwindow = iframe.contentWindow;
let utils = cwindow.QueryInterface(Ci.nsIInterfaceRequestor)
.getInterface(Ci.nsIDOMWindowUtils);
return new Promise(resolve => {
cwindow.addEventListener("load", function onLoad(aEvent) {
cwindow.removeEventListener("load", onLoad);
let sbWidth = {};
try {
utils.getScrollbarSize(true, sbWidth, {});
} catch (e) {
Cu.reportError("Could not sample scrollbar size: " + e + " -- " +
e.stack);
sbWidth.value = 0;
}
// Minimum width of 10 so that we have enough padding:
sbWidth.value = Math.max(sbWidth.value, 10);
resolve(sbWidth.value);
iframe.remove();
});
});
}
};
Object.freeze(this.ScrollbarSampler);
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