I want to change the theme displayed on login to be specified for a user.
I know that a custom menu can be different depending on the language used for the site. So I'm thinking that it's possible to apply this principal to other values on the site eg a value in a user profile field and also to wider theme characteristics.
So user Mary has abc in a user profile field and sees the site with Theme A
User Jonny has xyz in a user profile field and sees the site with Theme X
Alternatively this could be a single theme and trigger different stylesheets within it.
So I have a big idea but I don't know where to look to start this off. Where, for example, is the code that affects the custom menu change depending on language?
Oh and user themes are no good because users can change them.
Has anyone achieved the specific theme per user effect in another way that doesn't need coding?