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Your LimeSurvey version: 6.x
Own server or LimeSurvey hosting: own on premise
Survey theme/template: vanilla child theme
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While I was successful at writing my custom survey theme based on core Vanilla, I'm not able to understand how do I can override and extend core question themes.
I can understand I can slighty edit graphical appearance by altering their css into my custom.css file. But how about altering html code?
Do I really need to write a full theme with config.xml and file structure from scratch? How do it can fit only with my custom survey theme, without altering other themes?
Also a note on Wiki documentation about Question themes is lacking of data, images are missing and existing images are obsolete, v3.x related. Maybe I can update it.
Thanks in advance
 

Question theme construction : you have to create a config.xml only. After you can replace (if you want) specific theme twig file.
By survey theme : just add needed twg file at tghe good place ./survey/ directory oin theme  github.com/LimeSurvey/LimeSurvey/tree/ma...ication/views/survey

Sorry Denis, I didn't completely got your comment.

let's assume i can do
./uploads/theme/question/mycustom-5pointschoice/config.xml

Do I need `<extends>5pointschoice</extends>` attribute?
Then, if I put identical `.twig` subview, will be overridden without disabling original theme?

That is not the correct location for the config file.

For inspiration, you can see several examples of question themes, including correct file structure here - github.com/tpartner?tab=repositories

 mycustom/uploads/theme/question/5pointchoice/config.xml

 

Ok, sorry for delayed reply.
So, what I can understand, a custom question theme is not overriding anything inside core.
But, by creating an appropriate directory structure, just a question theme can be a set of alternatives views for existing questions.

See this example (only for logged in users)

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I mean, there is no relationship between first "root" directory name and field <name> inside config.xml. So that makes you free to deliver many answers type in one theme. Is it? Why there is no documentation about this? Is it Yii framework stuff?

Question theme : create an alternative view, don't replace core
Question plugin : can replacve core or anything else
Survey theme /survey/questions/answer/questiontype/answer.twig : replace core (and maybe question theme : not tested) : i use it to doiable upload question type in 3.X for example.

> So that makes you free to deliver many answers type in one theme.

Don't understand

> Why there is no documentation about this?

take time (without money) : compare number of plugin in my gitlab and documentation/presentation website

> Is it Yii framework stuff?

Limesurey code (PHP) and Twig system : you can register different directory, and when twig call a file : it take each directory in order.
See : www.limesurvey.org/manual/GetPluginTwigPath