protocol: reorder wl_data_offer.source_actions and wl_data_device.enter

Most compositors send the wl_data_offer.source_actions event before the wl_data_device.enter event, i.e. after creation of the data offer. This contradicts to the wayland spec.

On the other hand, it's reasonable to send all the information useful to the client before the enter event, rather than send mime types before the enter event and source actions (that don't depend on drop target) after the enter event.

On the client side, toolkits such as Qt and GTK already expect to see the source actions before receiving the enter event.

Given all of that, this change adjusts the spec to match the behavior observed in the compositors in the wild.

Signed-off-by: Vlad Zahorodnii vlad.zahorodnii@kde.org

closes #322 (closed)