zulip/static/js/pointer.js

// See https://zulip.readthedocs.io/en/latest/subsystems/pointer.html for notes on
// how this system is designed.

exports.initialize = function initialize() {
    $(document).on('message_selected.zulip', function (event) {
        if (event.id === -1) {
            return;
        }

        if (event.mark_read && event.previously_selected !== -1) {
            // Mark messages between old pointer and new pointer as read
            let messages;
            if (event.id < event.previously_selected) {
                messages = event.msg_list.message_range(event.id, event.previously_selected);
            } else {
                messages = event.msg_list.message_range(event.previously_selected, event.id);
            }
            if (event.msg_list.can_mark_messages_read()) {
                unread_ops.notify_server_messages_read(messages, {from: 'pointer'});
            }
        }
    });
};

window.pointer = exports;