XDND is one of the many drag and drop protocols used in X Window System.

It is relatively widely supported in the new applications; For example, GTK+, Qt, WindowMaker, Mozilla and GNOME support it.

Here's an example of how it works, shortened version of the example that's in the home page:

  • Windows that support XDnD have property XdndAware.
  • When drag begins, the source takes ownership of XdndSelection. When mouse enters XdndAware window, the source sends an XdndEnter ClientMessage to the window. This has the protocol version number.
  • Target receives the XdndEnter.
  • Source sends XdndPosition ClientMessage (position of the mouse, type of the action).
  • Target receives XdndPosition, figures out where the data has been dropped to, and decides whether or not to accept it.
  • Target sends XdndStatus to source, telling in it whether or not it accepted it and what it decided to do with it.
  • Source receives XdndStatus.
  • If the mouse leaves the window or something similiarly silly happens, source sends XdndLeave ClientMessage.
  • Target receives XdndLeave, frees data and forgets that the whole thing happened. (Yes, that's how the web page phrases it =)

The same call, XConvertSelection(), can be used to process both Clipboard and XDnD, while from user point of view, using XDnD won't mess up the X selections. Cool, huh? =) Also, XDnD ignores old protocol versions; this probably makes it safer against malfunctioning programs.

Currently, the home page is here:
http://www.newplanetsoftware.com/xdnd/

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