[PATCH wayland v4] protocol: Add DnD actions

[Mike Blumenkrantz]

On Fri, 16 Oct 2015 16:52:44 +0100
Daniel Stone <daniel at fooishbar.org> wrote:

> Hi,
> 
> On Wednesday, 30 September 2015, Carlos Garnacho <carlosg at gnome.org>
> wrote:
> 
> > These 2 requests have been added:
> >
> > - wl_data_source.set_actions: Notifies the compositor of the
> > available actions on the data source.
> > - wl_data_offer.set_actions: Notifies the compositor of the
> > available actions on the destination side, plus the preferred
> > action.
> >
> > Out of the data from these requests, the compositor can determine
> > the action
> > both parts agree on (and let the user play a role through eg.
> > keyboard modifiers). The chosen option will be notified to both
> > parties through the following two requests:
> >
> > - wl_data_source.action
> > - wl_data_offer.action
> >
> > In addition, the destination side can peek the source side actions
> > through wl_data_offer.source_actions.
> >
> > Compared to the XDND protocol, there's two notable changes:
> >
> > - XDND lets the source suggest an action, whereas wl_data_device
> > lets the destination prefer a given action. The difference is
> > subtle here, it comes off as convenience because it is the drag
> > destination which receives the motion events (unlike in X) and can
> > perform action updates.
> >
> >   The drag destination seems also in a better position to update the
> >   preferred action based on things like the data being transferred,
> > the place being dropped, and whether the drag is client-local.
> >
> > - That same source-side preferred action is used in XDND to convey
> > the modifier-induced action to the drag destination, which would
> > then ack it, or reply with another action that's accepted (or
> > none), this makes the XdndPosition/XdndStatus messaging very
> > verbose, and synchronous because the drag source always needs to
> > know the latest status/action for every position+action sent.
> >
> >   Here it's the compositor which takes care of modifiers and
> > matching available/accepted actions, this allows for the signaling
> > to happen only whenever the actions/modifiers change for real.
> >
> > Roughly based on previous work by Giulio Camuffo
> > <giuliocamuffo at gmail.com <javascript:;>>
> >
> 
> Mike had a look at this from EFL - CCing him.
> 
> Cheers,
> Daniel

Hi,

Having reviewed this, and also having fully implemented the current DND
protocol, I think that this is a good idea and would be a worthwhile
addition. I have no suggestions for modifications or trivial
bikeshedding.

Regards,
Mike