Add avathar.recenttopicsav.modify_ads_code event to allow third-party ad content providers

[avandenberghe]

Background

Issue #160 added a built-in advertisement block to Recent Topics (ACP toggle + HTML textarea, rendered via ADS_INDEX_CODE in the index template). The pbwowext extension has had the same feature since earlier, also assigning ADS_INDEX_CODE via core.page_header.

Because core.index_modify_page_title (Recent Topics) fires after core.page_header (pbwowext), Recent Topics currently overwrites pbwowext's assignment silently. There is no way for pbwowext to act as a content provider for the ad block without this race condition.

Proposal

Fire a new PHP event avathar.recenttopicsav.modify_ads_code in core/recenttopics.php just before assigning ADS_INDEX_CODE to the template.

$vars = ['ads_index_code'];
extract($this->dispatcher->trigger_event('avathar.recenttopicsav.modify_ads_code', compact($vars)));

• ads_index_code is pre-populated with Recent Topics' own configured value (from rt_ads_enable / rt_ads_code), or false if disabled
• A listener can read and override ads_index_code to inject content from another source
• If no listener overrides it, behaviour is identical to today

Effect

• pbwowext can listen to this event and inject its own ad content, removing the need for it to assign ADS_INDEX_CODE directly in core.page_header
• Any other extension can also use this event to provide ad content
• Recent Topics' own ACP ad settings serve as the default when no listener overrides

Related

• Add optional advertisement block on forum index page #160 — original ad block implementation
• avatharbe/pbwowext — companion issue for the listener side