Can alternate content be loaded asynchronously?

If you output a lot of alternate blocks within your ODD, e.g. for places, people or terms, it can slow down rendering of the text, in particular, if the content to be shown as alternate requires further processing or is loaded from an external database system via an API.

To help with this, the pb-popover webcomponent allows popup content to be loaded asynchronously. pb-popover is the default component which is output for <model behaviour="alternate">.

To use this feature, change your model to use a template expression instead of the alternate behaviour. In the template, output a pb-popover and give it an attribute remote, containing the URL from which the content for this particular popover should be loaded. The popover will then defer loading content until it is actually shown.

For example, the following elementSpec outputs a pb-popover for any placeName having an @ref attribute. Instead of constructing the contents of the alternate immediately, it just outputs a loading message. The remote="api/places/[[ref]]" attribute specifies the endpoint from which the actual content will be loaded once the popover is displayed. The @ref is passed to the endpoint as last path component.

<elementSpec ident="placeName" mode="add">
    <model behaviour="inline" cssClass="place" predicate="@ref">
        <param name="ref" value="@ref"/>
        <pb:template xmlns="" xml:space="preserve">
            <pb-popover remote="api/places/[[ref]]">[[content]]<span slot="alternate">Loading ...</span></pb-popover>
    <model behaviour="inline"/>

For sure this assumes that you created a custom API endpoint /api/places/{ref} on your TEI Publisher instance.