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

[Michael Catanzaro]

On Wed, 2015-09-30 at 17:43 -0500, Michael Catanzaro wrote:
> Minor issue: this and the next patch introduce the requirement that
> accept is called on the data offer before the mouse grab is released.
> I
> now see this has always been required by mutter -- not sure why --
> but
> it's new for Weston. (In fact, sending accepts has always been
> optional.) The new restriction seems a bit arbitrary and could be
> hard
> for some clients. Chrome's cross-platform DnD abstraction all but
> requires drag data to have been received before it can determine
> whether to accept a mime type, so Chrome doesn't send an accept until
> it's done receiving. Previously, that just meant the cursor would not
> be updated in response to motion events during that time, but now it
> means the drop will fail. This is not a huge deal, and the other
> changes in these patches are much more important, but it suggests we
> shouldn't add this restriction unless there's a good reason behind
> it... and I don't know of one, so I'd like to understand that. The
> change isn't necessary for the protocol as-is, and doesn't seem
> necessary for DnD actions, either?

Thinking about this more, there is at least an obvious workaround: I
can just send a bogus accept after receiving the drag_enter event (and
then change it once the data is received.)