At Acquia, among other Drupal 7 UX improvements, we've been working making the overlays work as designed by Mark Boulton and Leisa Reichelt. The plan includes a header with two levels of fixed items, which all invoke overlays (almost full window popups), showing above the current page. Instead of reinventing the wheel, we started working towards porting the existing Popups module to Drupal 7 and implementing the Drupal 7 overlay looks via a skin, so we can leverage the existing work, testing and wisdom from the module.
Due to how hard JS is to debug still with Firebug, we faced some issues, but given that we are over those, we have the basic overlay looks ready and facing some other engineering problems which are pretty much standard with how the Popups module works. For integration purposes (and because our proof of concept version of the header did not look as good), we worked with Young Hahn's header patch. You can find my modifications to that to work with overlays on the issue. While Young's patch does not yet map to the D7UX plan to have a fixed set of top level items and a fixed set of lower level items, redefining the D7 admin information architecture, for working out the overlay, it is pretty good as it is now.
Since we were working on (a) porting Popups module to Drupal 7, (b) create a d7ux skin for it, (c) a header which we did not use in this experiment, and Young Hahn was working on a header which needs a patch and images added, I've decided to pull together a quick Drupal package for your testing pleasure. The distribution includes a D7UX install profile which should be used so that the proper modules are set up. It also includes the latest header patch from Young's issue (which has my popups class modifications) and the images and sprite from there. The ported Popups module and the D7UX skin for it is also included.
While I am searching for the best ways to collaborate on the overlay (and possibly also on the header), so we don't need to work back and forth in issue queues, possibly stepping on each other's toes, I am also sharing the D7UX Popups module theme as a separate package, so those fond of applying patches and adding up images from different sources can keep up with development.
There are some pretty significant known issues with the overlay/popups. The biggest one being that since the overlay page is loaded into the same DOM tree (same HTML document) as the rest of the page, ID collissions can easily apply. If you load up a node edit form on a page with a node edit form, #node-edit will appear twice. Behaviours rightly assume that an HTML ID will ever appear once, so they do not expect this situation. This breaks some behaviors. Also, since Popups modules opens new popups on clicking on new links without closing the previous ones, this can also happen if you open two node forms in the popup in a page view. There are also smaller styling problems (eg. overlays on lower layers move up a few pixels when new popups are opened), but we should focus on the significant issues first.
I am looking at breaking down the Popups module (again) to core patches so its parts can be included in core. That would assume that the basic working of it (loading up new HTML-particles into the same HTML document) can be made work without major issues. The great maintainer of Popups module, Tao Starbow worked on quite a few core patches, but unfortunately those got the fate of the overdebated. The issues were split up, then some of the individual pieces were discussed to be over-generalized and in other areas, the scope of Popups in core was narrowed considerably to some confirm forms. No doubt Tao got burnt out from there.
That was way before Mark and Leisa suggested using the overlay technique for the Drupal 7 administration UI. I hope we can revive and refocus some of the issues and get this effort going faster, so we can focus on usability of the actual admin screens showing up in the overlays. Rendering API, JS and CSS wizards welcome! Look for my upcoming blog post on a plan to get this into core!