[Qt-interest] Drag and Drop Pointers/QModelIndex Within Application

[Robert Hairgrove]

Karol Krizka wrote:
> Hi there,
> 
> I'm basically trying to add a DnD interface to my application. I do not
> need to be able to drag/drop outside of the application.
> 
> I basically have a list of categories, each with a set of items
> organizes in a tree (QTreeView). I want to be able to move the items
> between the categories by dragging and dropping them. I thought the best
> idea would be to pass the QModelIndex of the items being dragged in the
> DnD event and then in the dropAction, I would figure out where the index
> came from and where it was dropped, then perform the move. Another idea
> was that I pass the pointer to the item.
> 
> However, the data for a DnD event seems to be passed via the QMimeData
> structure, which only supports data in the format of color, string, html
> or a bytestream.
> 
> So, what is the best way to pass data using DnD inside an application?
> 
> --
> Cheers,
> Karol Krizka
> http://www.krizka.net

You can register your own class as a new mime data type, but you must 
implement the streaming operators for it (i.e., << and >>). It is very 
easy to do, though.

Open QtAssistant and read the "Drag and Drop" overview as well as the 
description of the QMimeData and QDropEvent classes. There are many 
examples there.