Re: gtk 1.1.[12,13]: motiv and xdnd DND callback order

[Owen Taylor <otaylor redhat com>]

Rasca Gmelch <thron@gmx.de> writes:

> i've some problems to understand the order in which the DND
> callbacks are called.
> 
> inside a gtk ctree widget i get the following debug output
> from my program:
> 
> on_drag_begin()
> on_drag_motion()
> on_drag_data_get()
> on_drag_data()
> on_drag_data_delete()
> on_drag_data_leave()

This is hard to understand because it is a mix of client
side and target side calls.  (is on_drag_data() 
"drag_data_received" ?) But it looks approximately correct.

> sounds quite good, isn't it?
> in on_drag_data_leave() i reset a value which i need to make
> same visual effects during drag_motion(). but that doesn't work
> during a motiv DND (motiv -> ctree) operation, cause there the
> order is in this way:
> 
> on_drag_motion()
> on_drag_leave()
> on_drag_data()
> 
> the "drag_data_received" callback is called *after* the leave-callback :(
> is that a bug or a feature or do i have to do special things in
> my code to ensure that the drag_leave comes at the right time??

Basically, I'd say you shouldn't count on the ordering
of "drag_data_received" and "leave". 

The two guarantees are:

 1a) If you specify GTK_DEST_DEFAULT_DROP in the flags, then
     you will get a "drag_data_received" signal if you
     receive valid data. 

 1b) If you don't specify GTK_DEST_DEFAULT_DROP, then you
     will always get a "drag_data_received" call when
     you call gtk_drag_get_data(), which will either
     indicate success or failure. 
     (Failure by selection_data->length < 0)

 2) If you received "drag_motion" events, you will get a 
    "drag_leave" event.

Regards,
                                        Owen