Theme modifiers: A brief introduction

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As themes become more ambitious, we’ve been looking for ways to allow them to manipulate core server-side behaviour. While they will never be given the same level as control as plugins, we can provide some predefined hooks for themes to manipulate.

Introducing: theme modifiers :partying_face:

They are specified using the modifiers key in your theme’s about.json file.

For a 100% up-to-date list of modifiers, check the database schema at the bottom of theme_modifier_set.rb, but here’s a quick summary of what we have so far:

  • serialize_topic_excerpts boolean (default false) - always include excerpts when serializing topic lists

  • csp_extensions string array - add directives to the CSP. Works the same as the old “extend_content_security_policy” theme-setting method. But remember, simple <script> src=""> tags are allowed automatically.

  • svg_icons string array - a list of icons which should be included in the icon subset

  • topic thumbnails array of dimensions - request additional resolutions in the topic thumbnail set. Note that they are generated asynchronously, so you must fall-back to the original image if your requested size is not provided. More information available in the commit message

One theme making heavy use of these new hooks is Topic List Thumbnails - Theme component - Discourse Meta - check out the code to see how it works.

This document is version controlled - suggest changes on github.