74 lines
2.4 KiB
JavaScript
74 lines
2.4 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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module.metadata = {
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"stability": "unstable"
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};
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const { Ci } = require("chrome");
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var { emit } = require("./core");
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var { when: unload } = require("../system/unload");
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var listeners = new Map();
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var getWindowFrom = x =>
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x instanceof Ci.nsIDOMWindow ? x :
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x instanceof Ci.nsIDOMDocument ? x.defaultView :
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x instanceof Ci.nsIDOMNode ? x.ownerDocument.defaultView :
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null;
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function removeFromListeners() {
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this.removeEventListener("DOMWindowClose", removeFromListeners);
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for (let cleaner of listeners.get(this))
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cleaner();
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listeners.delete(this);
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}
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// Simple utility function takes event target, event type and optional
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// `options.capture` and returns node style event stream that emits "data"
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// events every time event of that type occurs on the given `target`.
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function open(target, type, options) {
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let output = {};
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let capture = options && options.capture ? true : false;
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let listener = (event) => emit(output, "data", event);
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// `open` is currently used only on DOM Window objects, however it was made
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// to be used to any kind of `target` that supports `addEventListener`,
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// therefore is safer get the `window` from the `target` instead assuming
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// that `target` is the `window`.
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let window = getWindowFrom(target);
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// If we're not able to get a `window` from `target`, there is something
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// wrong. We cannot add listeners that can leak later, or results in
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// "dead object" exception.
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// See: https://bugzilla.mozilla.org/show_bug.cgi?id=1001833
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if (!window)
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throw new Error("Unable to obtain the owner window from the target given.");
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let cleaners = listeners.get(window);
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if (!cleaners) {
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cleaners = [];
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listeners.set(window, cleaners);
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// We need to remove from our map the `window` once is closed, to prevent
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// memory leak
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window.addEventListener("DOMWindowClose", removeFromListeners);
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}
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cleaners.push(() => target.removeEventListener(type, listener, capture));
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target.addEventListener(type, listener, capture);
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return output;
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}
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unload(() => {
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for (let window of listeners.keys())
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removeFromListeners.call(window);
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});
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exports.open = open;
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