From 307b23626d9fccc4ab9f72b23940f26c54505b0e Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Wed, 20 Feb 2019 14:03:55 +0100
Subject: protocol: disallow re-using wl_data_source

As pointed out in [1], re-using a wl_data_source for multiple start_drag or
set_selection requests has bad consequences, because this object has events
that allo tracking the state of a selection/drag-and-drop operation. Tracking
two operations at the same time isn't possible with this interface.

[1]: https://lists.freedesktop.org/archives/wayland-devel/2019-January/039936.html

Signed-off-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Daniel Stone <daniels@collabora.com>
---
 protocol/wayland.xml | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/protocol/wayland.xml b/protocol/wayland.xml
index 10e039d..17a1769 100644
--- a/protocol/wayland.xml
+++ b/protocol/wayland.xml
@@ -847,6 +847,7 @@
 
     <enum name="error">
       <entry name="role" value="0" summary="given wl_surface has another role"/>
+      <entry name="used_source" value="1" summary="source has already been used"/>
     </enum>
 
     <request name="start_drag">
@@ -876,6 +877,10 @@
 
 	The input region is ignored for wl_surfaces with the role of a
 	drag-and-drop icon.
+
+	The given source may not be used in any further set_selection or
+	start_drag requests. Attempting to reuse a previously-used source
+	may send a used_source error.
       </description>
       <arg name="source" type="object" interface="wl_data_source" allow-null="true" summary="data source for the eventual transfer"/>
       <arg name="origin" type="object" interface="wl_surface" summary="surface where the drag originates"/>
@@ -889,6 +894,10 @@
 	to the data from the source on behalf of the client.
 
 	To unset the selection, set the source to NULL.
+
+	The given source may not be used in any further set_selection or
+	start_drag requests. Attempting to reuse a previously-used source
+	may send a used_source error.
       </description>
       <arg name="source" type="object" interface="wl_data_source" allow-null="true" summary="data source for the selection"/>
       <arg name="serial" type="uint" summary="serial number of the event that triggered this request"/>
-- 
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