I need to make a native gtk application which has the functionality of virtual file drag and drop. What i mean here is that when we start dragging a file from the native application then that file actually doesn't exist there but is either generated or downloaded from some remote location and is finally available at the drop location.
The virtual drag drop is possible in windows , visit the below given link http://blogs.msdn.com/oldnewthing/archive/2008/03/19/8080215.aspx
I'm betting that the best thing for this is to use gtk with libcurl. I don't know of anything within gtk itself that will do this. It's also the unix-y way of doing things--that is, stringing well-focused tools together to accomplish a larger task.
I also just noticed this, but they compare themselves to a number of other similar libraries, and there are some interesting ones that seem to be more integrated with gtk. In particular, I'd point out GNet Library. It's protocol support doesn't seem as extensive as libcurl, but it's a part of gtk. I don't know how important that is to you.