[PATCH wayland] protocol: Improve data source notification around DnD progress

[Michael Catanzaro]

On Thu, 2015-10-01 at 21:57 +0200, Carlos Garnacho wrote:
> Remember, toolkits preserve some state. The drag source is in control
> of the pointer cursor as long as the DnD operation holds, so it
> should
> reset its internal current cursor to the regular one for the next
> time
> the pointer enters the surface. And that's the bare minimals to be
> done there, in X11-land toolkits usually implemented DnD and its
> cursor changes through a grab, at least in the case of GTK+ this is
> carried on, and brings in a lot more side effects than just an
> extraneous cursor, so really can't wait until the next
> wl_pointer.enter.

Perhaps you could elaborate on this, to make clear why
wl_data_source.drop_performed is essential? I think Bill assumes that
any action performed here could instead be delayed until the data
source is destroyed (which could be arbitrarily long) or until the next
enter event (same).

I guess I will partially answer my own question: you would need to
delete the drag data during a move operation, for one, which cannot be
so delayed.

Michael