bb5a4dc04d
Extracted the reflow tracking logic from the box-model to a dedicated util in inspector/shared/reflow-tracker.js to use it in both box-model and grid-inspector. MozReview-Commit-ID: DZCOH3RDY6
114 lines
2.6 KiB
JavaScript
114 lines
2.6 KiB
JavaScript
/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
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/* vim: set ts=2 et sw=2 tw=80: */
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/* 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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const { ReflowFront } = require("devtools/shared/fronts/reflow");
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/**
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* Simple utility class that listens to reflows on a given target if and only if a
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* listener is actively listening to reflows.
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*
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* @param {Object} target
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* The current target (as in toolbox target)
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*/
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function ReflowTracker(target) {
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this.target = target;
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// Hold a Map of all the listeners interested in reflows.
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this.listeners = new Map();
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this.reflowFront = null;
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this.onReflow = this.onReflow.bind(this);
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}
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ReflowTracker.prototype = {
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destroy() {
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if (this.reflowFront) {
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this.stopTracking();
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this.reflowFront.destroy();
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this.reflowFront = null;
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}
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this.listeners.clear();
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},
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startTracking() {
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// Initialize reflow front if necessary.
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if (!this.reflowFront && this.target.form.reflowActor) {
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let { client, form } = this.target;
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this.reflowFront = ReflowFront(client, form);
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}
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if (this.reflowFront) {
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this.reflowFront.on("reflows", this.onReflow);
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this.reflowFront.start();
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}
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},
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stopTracking() {
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if (this.reflowFront) {
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this.reflowFront.off("reflows", this.onReflow);
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this.reflowFront.stop();
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}
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},
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/**
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* Add a listener for reflows.
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*
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* @param {Object} listener
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* Object/instance listening to reflows.
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* @param {Function} callback
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* The associated callback.
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*/
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trackReflows(listener, callback) {
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if (this.listeners.get(listener) === callback) {
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return;
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}
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// No listener interested in reflows yet, start tracking.
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if (this.listeners.size === 0) {
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this.startTracking();
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}
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this.listeners.set(listener, callback);
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},
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/**
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* Remove a listener for reflows.
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*
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* @param {Object} listener
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* Object/instance listening to reflows.
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* @param {Function} callback
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* The associated callback.
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*/
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untrackReflows(listener, callback) {
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if (this.listeners.get(listener) !== callback) {
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return;
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}
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this.listeners.delete(listener);
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// No listener interested in reflows anymore, stop tracking.
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if (this.listeners.size === 0) {
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this.stopTracking();
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}
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},
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/**
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* Handler called when a reflow happened.
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*/
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onReflow() {
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for (let [, callback] of this.listeners) {
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callback();
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}
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},
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};
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module.exports = ReflowTracker;
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