Move mobile detection from PHP to JS to avoid cache issues

Problem/Motivation

When the "Prevent automatic opening on mobile devices" option is enabled, the Oswald Chatbot module currently determines whether a visitor is using a mobile device server-side in PHP (via MobileDetect and isMobileRequest()).

This leads to Varnish and page cache inconsistencies because:

The backend renders different HTML for mobile vs desktop visitors (open=true vs open=false in the embed script).

• Varnish caches only one variant per URL, so mobile users may receive the desktop version (which auto-opens the chat bubble), or vice versa.

As a result, the chatbot may open automatically on mobile screens, even when “prevent auto open on mobile” is enabled.

Proposed resolution

Move the entire device-specific decision (“open or not on mobile”) to the JavaScript layer, and make the backend deliver a single, cache-safe variant.

Key changes

1. PHP backend

   • OswaldChatbot::getAutoOpen() no longer performs device detection.

   • OswaldChatbot::getCacheTags() no longer includes device-dependent tags.

   • In OswaldChatbotController::attachAndInitialize():

     • The embed script always uses ?open=false (the Oswald script never auto-opens by itself).

     • Configuration values are passed via drupalSettings.oswald:

       [
         'autoOpen' => TRUE/FALSE,
         'preventAutoOpenMobile' => TRUE/FALSE,
         'mobileBreakpoint' => (int) $chatbot->get('mobile_breakpoint')->value ?: 768,
       ]

   • Added a new base field mobile_breakpoint (integer, default 768) so site builders can define what screen width counts as “mobile”.

   • Added update hook oswald_update_91004() to install this new field for existing entities.

2. JavaScript

   • oswald.js now handles viewport detection using window.matchMedia('(max-width: Xpx)').

   • The decision logic runs client-side:

     var shouldOpen = shouldOpenByUrl ||
       (autoOpen && (!isMobile || !preventAutoOpenMobile));

   • This ensures:

     • On desktop: chat opens automatically if enabled.

     • On mobile: chat stays closed when “prevent auto open on mobile” is checked.

     • With ?openOswaldWidget=true: chat always opens (manual override).

   • oswald.libraries.yml updated to include dependency core/drupalSettings.

3. Caching

   • Backend HTML is now identical for all devices → Varnish and Drupal page cache remain valid.

   • Only frontend JavaScript decides on behavior per viewport.