protocol: Clarify how clients can cancel a drag operation

Explicitly say that destroying a wl_data_source previously used in a
wl_data_device::start_drag request will cancel the DND session. This
is currently the only way to do it from client side (besides those
"indirect" ones already documented) and all compositors work like that
but it is not clear spec-wise it is the expected behaviour.

Signed-off-by: Nick Diego Yamane <nickdiego@igalia.com>

diff --git a/protocol/wayland.xml b/protocol/wayland.xml
index 09e4f4c..3475a79 100644 (file)
--- a/protocol/wayland.xml
+++ b/protocol/wayland.xml
@@ -829,7 +829,8 @@
        for the eventual data transfer. If source is NULL, enter, leave
        and motion events are sent only to the client that initiated the
        drag and the client is expected to handle the data passing
-       internally.
+       internally. If source is destroyed, the drag-and-drop session will be
+       cancelled.
 
        The origin surface is the surface where the drag originates and
        the client must have an active implicit grab that matches the