How can I implement 'subsessions', a.k.a. per-tab storage

I need a way of being able to do the following:

A web application has a variable called 'setting'.

When a user first connects to the application, setting should have a value of 'default'.

Setting can be changed in any page.

If a user middle-clicks to open a page in a 开发者_运维技巧new tab, that page's setting should be a copy of the current page's setting (a copy, not a reference to it).

If a user opens a new tab and types in the web app's URL, then that page's value of setting should be 'default'.

If a user left clicks a link, then the new page should have the same value for setting as the referring page (the same value, not a copy).

Implementation:

I can obviously do this with a nasty url hack (...?setting=foo), but this gets nasty when there are many settings.

Is there any 'per-tab' storage available on browsers.

Theory:

The theoretical underpinning for this behaviour is the concept of a subsession. All subsessions belong to the session. Subsessions have a parent, if their tab was opened by a middle click. If their page loaded by typing a URL in an empty tab, then the subsession has no parent. Settings can be stored in subsessions, and is a setting is not present in a subsession, the parent's value is used instead.

Has anyone got any ideas on how to do this nicely?

Are there any sites which already behave this way?

Thanks,

Chris.

I think this would work for you: http://www.xul.fr/en/html5/sessionstorage.php

I have written a solution to this issue at:

https://github.com/chrisdew/subsession

It is obviously in early development and may contain bugs.