144 lines
4.4 KiB
JavaScript
144 lines
4.4 KiB
JavaScript
/* global Whisper, Backbone, _, $ */
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// eslint-disable-next-line func-names
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(function() {
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'use strict';
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window.Whisper = window.Whisper || {};
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Whisper.MessageListView = Backbone.View.extend({
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tagName: 'ul',
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className: 'message-list',
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template: $('#message-list').html(),
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itemView: Whisper.MessageView,
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events: {
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scroll: 'onScroll',
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},
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// Here we reimplement Whisper.ListView so we can override addAll
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render() {
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this.addAll();
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return this;
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},
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// The key is that we don't erase all inner HTML, we re-render our template.
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// And then we keep a reference to .messages
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addAll() {
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Whisper.View.prototype.render.call(this);
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this.$messages = this.$('.messages');
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this.collection.each(this.addOne, this);
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},
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initialize() {
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this.listenTo(this.collection, 'add', this.addOne);
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this.listenTo(this.collection, 'reset', this.addAll);
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this.render();
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this.triggerLazyScroll = _.debounce(() => {
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this.$el.trigger('lazyScroll');
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}, 500);
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},
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onScroll() {
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this.measureScrollPosition();
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if (this.$el.scrollTop() === 0) {
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this.$el.trigger('loadMore');
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}
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if (this.atBottom()) {
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this.$el.trigger('atBottom');
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} else if (this.bottomOffset > this.outerHeight) {
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this.$el.trigger('farFromBottom');
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}
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this.triggerLazyScroll();
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},
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atBottom() {
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return this.bottomOffset < 30;
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},
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measureScrollPosition() {
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if (this.el.scrollHeight === 0) {
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// hidden
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return;
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}
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this.outerHeight = this.$el.outerHeight();
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this.scrollPosition = this.$el.scrollTop() + this.outerHeight;
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this.scrollHeight = this.el.scrollHeight;
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this.bottomOffset = this.scrollHeight - this.scrollPosition;
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},
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resetScrollPosition() {
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this.$el.scrollTop(this.scrollPosition - this.$el.outerHeight());
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},
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restoreBottomOffset() {
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if (_.isNumber(this.bottomOffset)) {
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// + 10 is necessary to account for padding
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const height = this.$el.height() + 10;
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const topOfBottomScreen = this.el.scrollHeight - height;
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this.$el.scrollTop(topOfBottomScreen - this.bottomOffset);
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}
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},
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scrollToBottomIfNeeded() {
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// This is counter-intuitive. Our current bottomOffset is reflective of what
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// we last measured, not necessarily the current state. And this is called
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// after we just made a change to the DOM: inserting a message, or an image
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// finished loading. So if we were near the bottom before, we _need_ to be
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// at the bottom again. So we scroll to the bottom.
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if (this.atBottom()) {
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this.scrollToBottom();
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}
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},
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scrollToBottom() {
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this.$el.scrollTop(this.el.scrollHeight);
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this.measureScrollPosition();
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},
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addOne(model) {
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// eslint-disable-next-line new-cap
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const view = new this.itemView({ model }).render();
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this.listenTo(view, 'beforeChangeHeight', this.measureScrollPosition);
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this.listenTo(view, 'afterChangeHeight', this.scrollToBottomIfNeeded);
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const index = this.collection.indexOf(model);
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this.measureScrollPosition();
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if (model.get('unread') && !this.atBottom()) {
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this.$el.trigger('newOffscreenMessage');
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}
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if (index === this.collection.length - 1) {
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// add to the bottom.
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this.$messages.append(view.el);
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} else if (index === 0) {
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// add to top
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this.$messages.prepend(view.el);
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} else {
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// insert
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const next = this.$(`#${this.collection.at(index + 1).id}`);
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const prev = this.$(`#${this.collection.at(index - 1).id}`);
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if (next.length > 0) {
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view.$el.insertBefore(next);
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} else if (prev.length > 0) {
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view.$el.insertAfter(prev);
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} else {
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// scan for the right spot
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const elements = this.$messages.children();
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if (elements.length > 0) {
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for (let i = 0; i < elements.length; i += 1) {
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const m = this.collection.get(elements[i].id);
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const mIndex = this.collection.indexOf(m);
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if (mIndex > index) {
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view.$el.insertBefore(elements[i]);
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break;
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}
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}
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} else {
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this.$messages.append(view.el);
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}
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}
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}
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this.scrollToBottomIfNeeded();
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},
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});
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})();
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