signal-desktop/js/views/message_list_view.js

/*
 * vim: ts=4:sw=4:expandtab
 */
(function () {
    'use strict';
    window.Whisper = window.Whisper || {};

    Whisper.MessageListView = Whisper.ListView.extend({
        tagName: 'ul',
        className: 'message-list',
        itemView: Whisper.MessageView,
        events: {
            'add': 'onAdd',
            'update *': 'scrollToBottom',
            'scroll': 'measureScrollPosition',
            'reset-scroll': 'resetScrollPosition'
        },
        onAdd: function() {
            this.$el.removeClass('loading');
            this.scrollToBottom();
        },
        measureScrollPosition: function() {
            if (this.el.scrollHeight === 0) { // hidden
                return;
            }
            this.scrollPosition = this.$el.scrollTop() + this.$el.outerHeight();
            this.scrollHeight = this.el.scrollHeight;
            this.shouldStickToBottom = this.scrollPosition === this.scrollHeight;
        },
        resetScrollPosition: function() {
            var scrollPosition = this.scrollPosition;
            if (this.scrollHeight !== this.el.scrollHeight) {
               scrollPosition = this.el.scrollHeight * this.scrollPosition / this.scrollHeight;
            }
            this.$el.scrollTop(scrollPosition - this.$el.outerHeight());
        },
        scrollToBottomIfNeeded: function() {
            if (this.shouldStickToBottom) {
                this.$el.scrollTop(this.scrollHeight);
            }
        },
        scrollToBottom: function() {
            // TODO: Avoid scrolling if user has manually scrolled up?
            this.$el.scrollTop(this.el.scrollHeight);
            this.measureScrollPosition();
        },
        addAll: function() {
            Whisper.ListView.prototype.addAll.apply(this, arguments); // super()
            this.scrollToBottom();
        }
    });
})();