Most themes place the icon of the current application somewhere on the titlebar. Some operating systems (notably OS X) allow you to drag this icon as if it was the very file which is being viewed in that window.
This behaviour has been suggested for Metacity in the past. One of the two main problems with implementing it is that we have no way to identify the document being viewed in a window; we only barely have a way to identify the application.
In a blog post last week, Michal Hruby suggests a new window property to indicate the URI of a window’s current document. This spilled out onto wm-spec-list this morning. (“NEW” in the title is a typo for “NET”.)
Such a property is a matter for the toolkit to set, rather than the window manager. But if it was available, it would make the lives of window managers a little easier: not only would it make the window icon dragging possible, but it would also allow window matching by document or even document type, as well as by application.
Photo © Glamhag, cc-by-nc-sa.
Window matching by position ? (hint geouri and remote shells ;)