This patch enables basic drag&drop between applications.
You initiate a drag by creating a GDragOperation object and calling
exec() on it. This creates a nested event loop in the calling program
that only returns once the drag operation has ended.
On the receiving side, you get a call to GWidget::drop_event() with
a GDropEvent containing information about the dropped data.
The only data passed right now is a piece of text that's also used
to visually indicate that a drag is happening (by showing the text in
a little box that follows the mouse cursor around.)
There are things to fix here, but we're off to a nice start. :^)
Also, use the model_column() internally for selection as well as for
painting to keep things consistent.
Note that we always fire the on_context_menu_request hook, even if you
didn't click on an item. In those cases, you get a GModelIndex().
This macro goes at the top of every CObject-derived class like so:
class SomeClass : public CObject {
C_OBJECT(SomeClass)
public:
...
At the moment, all it does is create an override for the class_name() getter
but in the future this will be used to automatically insert member functions
into these classes.
