agl-shell: Add bound_ok and bound_fail events and a default destructorsandbox/mvlad/agl-shell-v2-bind-events-destructor

As we're increasing the amount of combinations we could have in the AGL
platforms, in which we're mixing various platforms, we require a way
to tell clients that there's already a shell client which is charge.

We can't really have multiple shell clients managing the windows and
surfaces but in the same time we don't want to sever the waylad
connection the way it happens in the first version of this protocol
interface. Racy alternatives might exist, which basically avoids
advertising the interface altogether once a client did bind to the
interface but that's not really a viable solution.

So, instead of doing that, this patch introduces two new events which
tells either client that it was either successful, and it can continue
issue requests and receive events and a fail event.

While doing an update to protocol, to add those two events add also
a default destructor for the protocol.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>

1 files changed, 45 insertions, 3 deletions

diff --git a/protocol/agl-shell.xml b/protocol/agl-shell.xml
index 11a65a1..f540eff 100644
--- a/protocol/agl-shell.xml
+++ b/protocol/agl-shell.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <protocol name="agl_shell">
   <copyright>
-    Copyright © 2019 Collabora, Ltd.
+    Copyright © 2019, 2022 Collabora, Ltd.
 
     Permission is hereby granted, free of charge, to any person obtaining a
     copy of this software and associated documentation files (the "Software"),
@@ -22,10 +22,35 @@
     FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
     DEALINGS IN THE SOFTWARE.
   </copyright>
-  <interface name="agl_shell" version="1">
-    <description summary="user interface for weston-ivi">
+  <interface name="agl_shell" version="2">
+    <description summary="user interface for Automotive Grade Linux platform">
+      Starting with version 2 of the protocol, the client is required to wait
+      for the 'bound_ok' or 'bound_fail' events in order to proceed further.
+
+      In case the client gets a 'bound_fail' event then it should consider that
+      there's another client already bound to the agl_shell protocol.
+      A client that receives a 'bound_ok' event should consider that there's
+      no other client already bound to the interface and can proceed further.
+
+      If the client uses an older version of the protocol it will receive
+      automatically an error and the compositor will terminate the connection,
+      if there's another client already bound the interface.
+
+      If the client receives the 'bound_fail' event and attempts to use the
+      interface further it will receive an error and the compositor will
+      terminate the connection. After the 'bound_fail' event was received the
+      client should call the destructor, which has been added with version 2
+      of the protocol. The client is free to try at a later point in time to
+      see if it will receive the 'bound_ok' event, but there's no explicit way
+      of finding out when that event will delivered. It is assumed that it can
+      infer that information through other means/other channels.
     </description>
 
+    <request name="destroy" type="destructor" since="2">
+      <description summary="destroys the factory object">
+      </description>
+    </request>
+
     <enum name="error">
       <entry name="invalid_argument" value="0"/>
       <entry name="background_exists" value="1"/>
@@ -113,5 +138,22 @@
       <arg name="app_id" type="string"/>
       <arg name="output" type="object" interface="wl_output"/>
     </request>
+
+    <event name="bound_ok" since="2">
+     <description>
+        Informs the client that it was able to bind the agl_shell
+        interface succesfully. Clients are required to wait for this
+        event before continuing further.
+     </description>
+    </event>
+
+    <event name="bound_fail" since="2">
+      <description>
+        Informs the client that binding to the agl_shell interface was
+        unsuccesfull. Clients are required to wait for this event for
+        continuing further.
+      </description>
+    </event>
+
   </interface>
 </protocol>