Drag And Drop The Hard Way

Disobedience, DisOrder's GUI client, uses a GtkTreeView to display its current queue of tracks (and for various other purposes). It allows rearrangement of the queue by drag and drop. The high-level support for this in GtkTreeView is rather unsatisfactory for two reasons:

1. You can only drag one track (row) at a time. It should be possible to drag the whole selection.
2. You cannot drag between widgets. Playlist editing in particular is likely to make this important.

(Actually the model where it reports the effects of the drag and drop by inserted/deleted signals on the underlying model is also quite inconvenient for me: Disobedience has to translate it back into a move which it communicates to the server.)

Fixing this involves doing rather a lot of the drag-and-drop work yourself, and while the documentation does exist it is not always clear or even complete. There is existing code out there, and I referred to it while working some of this out; but describing it in English online seems worthwhile. In addition, while some of the code is inextricably mixed with Disobedience's internal workings, a couple of independent modules are presented, which should be usable in other C programs.

This articles assumes some familiarity with GTK+. I have tried as far as reasonably possible to remove DisOrder-specific issues from the discussion here, but note that this isn't always possible.

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