--- myst: html_meta: "description": "Configure Blicca patterns site-wide with the plone.patternoptions registry record, without writing any JavaScript." "property=og:description": "Configure Blicca patterns site-wide with the plone.patternoptions registry record, without writing any JavaScript." "property=og:title": "Overrides without JavaScript" "keywords": "Plone, Blicca, patternoptions, registry, pattern options, markspeciallinks" --- (blicca-pattern-options-label)= # Overrides without JavaScript Many customizations don't need a single line of JavaScript. In this chapter, we make external links open in a new window, site-wide, with pure XML. ## How pattern options travel The registry record `plone.patternoptions` is a dictionary that maps a pattern name to a JSON string of options. Plone renders each entry as a `data-pat-` attribute on the `` element. The pattern's options parser walks up the DOM tree, so every pattern element inherits these options. Plone itself uses this mechanism, and configures `pickadate` and `plone-modal` this way. ## Exercise: change options through the web Open {menuselection}`Site Setup --> Management --> Configuration Registry` and search for `plone.patternoptions`. Add an entry with the key `markspeciallinks` and the value: ```json { "external_links_open_new_window": "true" } ``` Reload the page, and inspect the `` element in the developer tools. Notice the new `data-pat-markspeciallinks` attribute. External links in the content area now open in a new window. ## Persist it in a GenericSetup profile A through-the-web change lives in the database only. We persist it in the add-on's profile instead, in {file}`profiles/default/registry/patternoptions.xml`: ```xml {"external_links_open_new_window": "true"} ``` ```{important} Keep `purge="false"`. Without it, the import wipes the entries of the Plone core and of other add-ons. ``` ## The trigger class catch Options alone don't run a pattern. The trigger class must be present in the DOM. The `pat-markspeciallinks` class on the `` is only rendered when one of Plone's link settings is enabled. That's why the profile also enables `plone.mark_special_links` in {file}`profiles/default/registry/linksettings.xml`: ```xml True ``` When a pattern "does nothing", first check the trigger, then the options. ## Precedence An entry in `plone.patternoptions` overrides the `` attribute that Plone's `IPatternsSettings` adapters render for the same pattern. This includes the link settings from the control panel. This is powerful, so be deliberate. ## Checkpoint External links open in a new tab, and you did not run any build.