dropping content onto Plasma

[Sebastian Kügler]

The short version

Is there a way to offer plasma applet creation based on mimetypes of content 
dropped onto Plasma also for URLS?


The Good

I think that dropping "random" content on the desktop is a very strong UI 
metaphor. If we can make Plasma accept and Do The Right Thing was all kinds of 
content, that'll make for a nicely self-explaining interface.
It already works nicely with files. Basically, the applet registers the 
mimetypes it understands and makes sure it loads those, they're passed as args 
to the constructor. Plasma creates an applet accordingly when we drop 
something onto the desktop, or offers applets that "understand" and display 
the mimetypes when there's more than one.


The Bad

The above procedure works nicely for local content, such as files. URL's are a 
special kind of draggable content though. As far as I understand, a URL 
doesn't have a mimetype attached, it's either data + mimetype (+ other 
metainformation) or simply a URL.

In Lion Mail, I want to be able to drag emails from Lion Mail collections onto 
the desktop, and have them created there as loose emails. I don't want to pass 
the email itself around, just a reference to an email in the Akonadi database 
(which is a URL such as akonadi:?item=97881&type=).

Other things that should (at some point, in the future) work, and which I 
think are related:
- dropping a url to a website onto plasma should offer webbrowser
- dropping references to objects in nepomuk (contacts for example)
- dropping akonadi urls from mailody onto Plasma and load the email applet
- dropping a pdf from the web onto plasma, load previewer applet
- dropping a picture from a website, load picture frame applet

(The above, all to my knowledge, don't work right now.)
(Sidenote: For the Nepomuk and Akonadi URL case, we need either the type, or 
probe those database, items can be any kind of content.)


The Ugly

I'm working around this in Lion Mail right now by lying about the mimetype of 
the data the drop contains. I set the content type to the mimetype of the 
email (and register X-Plasma-DropMimeTypes=message/rfc822 in the .desktop 
file). I've put the URL into the data part. That obviously only works for 
emails dragged from Lion Mail (since that's where I'm doing that kind of crap 
in the first place) and it's the only thing in the world that assumes emails 
only contain akonadi URLs). Obviously, I'm not proud of that code. ;)


I'd like to have this fine mechanism also working URLs and be a bit smarter 
about that. I'm not sure about possible solutions, though. Guessing based on 
the dropped content would work for most cases (akonadi: as protocol is clear), 
but might be a bit tedious (impossible) to figure out for every mimetype in 
the world (especially if you start doing it based on file extensions). Probing 
mimetypes of remote files sounds icky to me as well. Maybe there is some code 
for this problem in KDE already?

Does anybody know a good solution for this? and
Where is that code in plasma? 
-- 
sebas

 http://www.kde.org | http://vizZzion.org |  GPG Key ID: 9119 0EF9 

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