Accessing software for Google Drive / Dropbox API / RemoteStorage apps?

Is there a way to gain isolated, user-selected access to a directory on any large file service without first gaining read-level access to their entire file system?

There's a lot of talk about "unburned" static web folders that allow users to access their data from a third party file service (Google Drive, Dropbox, their own server, etc.). The most notable effort I've found so far is remoteStorage.io , but there doesn't seem to be a way with any major provider a user selects a directory and then sandboxes it without breaking their trust (i.e. getting read access to all of its files).

From the user's point of view, the Webapp shouldn't be able to access anything else in the remote file store other than the folder the user grants access to (for example, I can give a text editor access to my FunnyJokes folder).

It seems that the current work will force the webapp to force a specific folder name ahead of time ("this application wants to access / appname _notes"), but this precludes the ability to tell the user where they might already have their notes.

Does anyone know a good way to do this using Google Drive, Dropbox or the like?

The user experience that matters the most to me is something like ...

• The user opens an unhosted webapp (for example, the basic text editor TextyApp). They press a button to connect to their data.
• A third party page (such as Google Drive) will appear that says "TextyApp has requested read / write access to your files. Please select a directory to use."
• Confirmation screen: "Grant read / write access to the FunnyJokes folder for TextyApp?"
• The page redirects back to the sandboxed webapp, accessing the user-specified folder and files inside it.

This is similar to how remote file storage is supposed to work, but I haven't found a way to do it yet. Any thoughts / suggestions would be great!

Cheers, Adam

Edit: To clarify, I'm not talking about keeping the " application data " hidden , but instead allows the user to specify a specific directory for the sandbox to use with the webapp that they don't want to give wider access.