Denis, can your twig replacement plugin be considerate as a fix for this bug?

Not really : because we can not "append" something to a existing twig file easily.

If we add something with "append" on twig renderer : it's fix the issue with maintenance mode or when user want to add HTML/twih on public page, but not "do something without showing HTML (log ? I donr't know current usage of beforeCloseHtml except adding HTML).

Maybe we need something for twig allowing expand to existing twig , but need to be cached (else : lot of memory if there are an event for each twig file)

See : https://github.com/LimeSurvey/LimeSurvey/pull/1079 related pull request too

Twig Blocks should make it easier
https://twig.symfony.com/doc/2.x/tags/extends.html

You added : getPluginsData https://github.com/LimeSurvey/LimeSurvey/blob/fa236596754dc6917aa4fb65108d7087594e7190/application/core/LSETwigViewRenderer.php#L296

It's done only for layout ? Right ?

Currently i redo renderMessage helper plugin to add an empty layout (to have somethong similar of renderPartial)
With getPluginsData : the string of plugin is added core string , then after html was closed … no ?

Since getAllContent return array of string made by plugins https://github.com/LimeSurvey/LimeSurvey/blob/fa236596754dc6917aa4fb65108d7087594e7190/application/libraries/PluginManager/PluginEventContent.php#L51

The event beforeTwigRenderTemplate didn't allow plugin to add content to sTwigBlocks …

https://github.com/LimeSurvey/LimeSurvey/pull/1097

Fix committed to master branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=27638

Release 3.14.2+180807