server side callback

[Giulio Camuffo]

Given it seems to me it's not clear how the additions in the spec
would work i'll write an example here:

we have two apps, S (source) and T (target).

S creates the wl_data_source, calls wl_data_source_offer with the
supported mime types and calls wl_data_source_set_actions with one or
more supported actions, using bitwise OR.

T gets the wl_data_offer, the wl_data_offer_offer events and the
wl_data_offer_actions with the actions set by
wl_data_source_set_actions.

T gets the drop event. T asks for the data and calls
wl_data_offer_accept_action with one of the supported actions, or the
ignore action. After this, after the server gets the accepted action,
the wl_data_source would need to be notified, by
wl_data_source_dropped, which carries the accepted action with it. In
QtWayland i can now exit the loop and give the accepted action to Qt.
But before doing that T calls wl_data_offer_finish which calls
wl_data_source_cancel on S's wl_data_source so it can be freed.

The problem is ensuring the wl_data_source_dropped gets called for
real after the server gets the accepted action.


2013/3/11 Giulio Camuffo <giuliocamuffo at gmail.com>:
> Hi all,
>
> I've been struggling with a problem these last few days: I'm working
> on QtWayland drag and drop support, and I noticed it requires some
> protocol additions, of which this is a draft: https://pastee.org/hxq26
> I want the" wl_data_source.dropped" event to be called after the
> wl_data_device receives and returns from the the drop event. The
> dropped event carries the action the target client chose, and i need
> to be able to set the action (by calling
> "wl_data_offer_accept_action") also from the "wl_data_device.drop"
> event. Hence, i cannot simply post the "wl_data_source.dropped" event
> just after the "wl_data_device.drop", because the
> "wl_data_offer_accept_action" would be processed too late.
>
> I could require the client to issue a request "notify_drop", at the
> end of the drop event listener, which would send the
> "wl_data_source.dropped", but a client that fails to do so would be
> troublesome: when a Qt client starts a drag it goes into a loop, which
> is exited only when the data is dropped. If the target client didn't
> send the "notify_drop" the source client would never exit from the
> loop, making it stuck.
> A timer could free it after some time, but that is not a good solution.
>
> What i need is a way to have a server-side callback when a certain
> client-side event listener returns, all inside libwayland-client,
> without the need for the client app to do anything. Is it possible?
> I'm willing to implement it, but I don't know wayland's internals and
> i'd need some pointing at.
>
> Thanks,
> Giulio