зеркало из https://github.com/mozilla/gecko-dev.git
91 строка
2.5 KiB
JavaScript
91 строка
2.5 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 file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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"use strict";
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this.EXPORTED_SYMBOLS = ["ScrollPosition"];
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const Ci = Components.interfaces;
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/**
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* It provides methods to collect and restore scroll positions for single
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* frames and frame trees.
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*
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* This is a child process module.
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*/
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this.ScrollPosition = Object.freeze({
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/**
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* Collects scroll position data for any given |frame| in the frame hierarchy.
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*
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* @param frame (DOMWindow)
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*
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* @return {scroll: "x,y"} e.g. {scroll: "100,200"}
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* Returns null when there is no scroll data we want to store for the
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* given |frame|.
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*/
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collect: function (frame) {
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let ifreq = frame.QueryInterface(Ci.nsIInterfaceRequestor);
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let utils = ifreq.getInterface(Ci.nsIDOMWindowUtils);
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let scrollX = {}, scrollY = {};
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utils.getScrollXY(false /* no layout flush */, scrollX, scrollY);
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if (scrollX.value || scrollY.value) {
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return {scroll: scrollX.value + "," + scrollY.value};
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}
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return null;
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},
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/**
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* Restores scroll position data for any given |frame| in the frame hierarchy.
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*
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* @param frame (DOMWindow)
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* @param value (object, see collect())
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*/
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restore: function (frame, value) {
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let match;
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if (value && (match = /(\d+),(\d+)/.exec(value))) {
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frame.scrollTo(match[1], match[2]);
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}
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},
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/**
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* Restores scroll position data for the current frame hierarchy starting at
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* |root| using the given scroll position |data|.
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*
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* If the given |root| frame's hierarchy doesn't match that of the given
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* |data| object we will silently discard data for unreachable frames. We
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* may as well assign scroll positions to the wrong frames if some were
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* reordered or removed.
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*
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* @param root (DOMWindow)
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* @param data (object)
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* {
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* scroll: "100,200",
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* children: [
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* {scroll: "100,200"},
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* null,
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* {scroll: "200,300", children: [ ... ]}
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* ]
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* }
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*/
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restoreTree: function (root, data) {
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if (data.hasOwnProperty("scroll")) {
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this.restore(root, data.scroll);
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}
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if (!data.hasOwnProperty("children")) {
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return;
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}
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let frames = root.frames;
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data.children.forEach((child, index) => {
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if (child && index < frames.length) {
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this.restoreTree(frames[index], child);
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}
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});
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}
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});
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