Add a sync_fence event to the export-dmabuf protocol.

unstable/wlr-export-dmabuf-unstable-v1.xml

@@ -36,7 +36,7 @@
     interface version number is reset.
   </description>
 
-  <interface name="zwlr_export_dmabuf_manager_v1" version="1">
+  <interface name="zwlr_export_dmabuf_manager_v1" version="2">
     <description summary="manager to inform clients and begin capturing">
       This object is a manager with which to start capturing from sources.
     </description>
@@ -59,7 +59,7 @@
     </request>
   </interface>
 
-  <interface name="zwlr_export_dmabuf_frame_v1" version="1">
+  <interface name="zwlr_export_dmabuf_frame_v1" version="2">
     <description summary="a DMA-BUF frame">
       This object represents a single DMA-BUF frame.
 
@@ -75,6 +75,9 @@
       responsible for closing the associated file descriptor.
 
       All frames are read-only and may not be written into or altered.
+
+      If a sync_fence event is received, clients must wait on the sync
+      fence to be signalled by the compositor before using the frame.
     </description>
 
     <enum name="flags">
@@ -141,9 +144,11 @@
 
     <event name="ready">
       <description summary="indicates frame is available for reading">
-        This event is sent as soon as the frame is presented, indicating it is
-        available for reading. This event includes the time at which
-        presentation happened at.
+        This event is sent as soon as all the data pertaining to the frame has
+        been received by the client. This event includes the time at which
+        the scanout began.
+        If a sync_fence object has been received, the clients must wait for it
+        to be signalled, otherwise the frame can be considered ready to be read.
 
         The timestamp is expressed as tv_sec_hi, tv_sec_lo, tv_nsec triples,
         each component being an unsigned 32-bit value. Whole seconds are in
@@ -199,5 +204,17 @@
         to close any FDs it has been given.
       </description>
     </request>
+
+    <!-- Version 2 additions -->
+
+    <event name="sync_fence" since="2">
+      <description summary="explicit synchronization fence">
+        This event provides a dma_fence kernel object which will be signalled
+        when the client can start sampling from the buffer.
+      </description>
+      <arg name="fd" type="fd"
+           summary="fence fd for last operation on buffer"/>
+    </event>
+
   </interface>
 </protocol>