Get HTML of selected link in a Mac OS X Service

I'm writing a Service that will be bundled with my application. The user should be able to right-click on a link in Safari (or another web browser) and call my Service and have it process the link (not just the text that gets selected when the user right-clicks).

The only thing I can't do is get the URL the link points to. The service method gives you an NSPasteboard to read from, which we'll call pboard.

The obvious thing to try to get the selected HTML would be [pboard stringForType:NSPasteboardTypeHTML], but that returned nil. So I called [pboard types], and it returned "public.utf8-plain-text" and NSStringPboardType. So it seems like this pasteboard only supports plain-text strings.

I tried calling [pboard addTypes:types ow开发者_如何转开发ner:self] (where types is an array containing NSPasteboardTypeHTML and nil), but it made no difference when I called stringForType:.

Can I somehow extract HTML from the pasteboard when [pboard types] only returns plain string types? Am I able to control what gets put onto the pasteboard and/or what gets read from it when my Service gets called?