If configured and possible, XenForo stores rendered CSS in a cache using the configured provider (Memcached, Redis, etc.) in \XF\CssRenderer::cacheFinalOutput
[php]
protected function cacheFinalOutput(array $templates, $output)
{
if (!is_string($output) || !strlen($output))
{
return;
}
if ($this->allowCached && $this->allowFinalCacheUpdate && $this->cache && $this->includeExtraParams)
{
$this->cache->save($this->getFinalCacheKey($templates), $output, 3600);
}
}
[/php]
Depending on the provider, the data might be compressed (using Memcached for example, OPT_COMPRESSION is enabled by default).
So when loading the cached rendered CSS, this data will be decompressed when loaded in \XF\CssRenderer::render
[php]
public function render($templates, $includeExtraParams = true)
{
[...]
$output = $this->getFinalCachedOutput($templates);
if (!$output)
{
[...]
}
return $output;
}
protected function getFinalCachedOutput(array $templates)
{
if (!$this->allowCached || !$this->cache || !$this->includeExtraParams)
{
return false;
}
$key = $this->getFinalCacheKey($templates);
return $this->cache->fetch($key);
}
[/php]
The only processing XenForo does afterwards is to add @charset "UTF-8" and two newlines in \XF\CssWriter::run
[php]
public function run(array $templates, $styleId, $languageId, $validation = null)
{
[...]
$output = $this->renderer->render($templates);
$output = $this->finalizeOutput($output);
return $this->getResponse($output);
}
public function finalizeOutput($output)
{
return '@charset "UTF-8";' . "\n\n" . $output;
}
[/php]
When finally sending the response and the client is capable, XenForo will compress the response with gzip level 1.
This seems inefficient as the data is decompressed and again compressed for every css.php request.
Ideally the data should be stored in cache with maximum compression and delivered to the client without intermediate decompression.
