GNOME Bugzilla – Bug 320814
Mac-like sheets
Last modified: 2010-07-10 03:16:26 UTC
http://developer.apple.com/documentation/UserExperience/Conceptual/OSXHIGuidelines/XHIGWindows/chapter_17_section_6.html#//apple_ref/doc/uid/20000961-BGBDHEID "A sheet is a modal dialog attached to a particular document or window, ensuring that the user never loses track of which window the dialog applies to" I can't think of any drawbacks (from a users point of view) with having sheets instead of free-floating modal dialogs.
Here's some discussion on the gtk mailing list about sheets: http://mail.gnome.org/archives/gtk-list/2004-July/msg00160.html
Mostly a window manager issue, I believe gnome-shell people were pondering something like this a while ago.
(In reply to comment #2) > Mostly a window manager issue, I believe gnome-shell people were pondering > something like this a while ago. Indeed. *** This bug has been marked as a duplicate of bug 612726 ***