Proposing new CHROMIUM_sync_point API.

gpu/GLES2/extensions/CHROMIUM/CHROMIUM_sync_point.txt

 Name
 
     CHROMIUM_sync_point
 
 Name Strings
 
     GL_CHROMIUM_sync_point
 
 Version
 
-    Last Modifed Date: February 25, 2013
+    Last Modifed Date: September 8, 2015
 
 Dependencies
 
     OpenGL ES 2.0 is required.
 
 Overview
 
     This extension allows a client to order operations between contexts.
 
     This extension implements a small subset of ARB_sync, with weaker
     guarantees. In particular it doesn't ensure commands are actually executed
     by the server, it only guarantees submission order.
 
     It does however guarantee operation order with respect to
     ConsumeTextureCHROMIUM and ProduceTextureCHROMIUM from
     CHROMIUM_texture_mailbox, if present.
 
 Issues
 
     None
 
-New Tokens
-
-    None
-
 New Procedures and Functions
 
     The command
 
         uint InsertSyncPointCHROMIUM()
 
-    flushes the stream of commands for the current context and creates and
-    inserts a sync point. The sync point acts as a fence, which is signaled when
-    previous commands have been submitted to the server, or when the context is
-    destroyed, whichever happens first. The sync point name is returned. The
-    sync point is implicitly deleted when it becomes signaled. The sync point
-    namespace is shared between all contexts on the same server, including other
-    context groups.
-
+    inserts a sync point insertion point in the current command stream. The

[piman, 2015/09/08 22:19:47]

nit: "inserts a sync point insertion point" doesn't read very well. I could be
useful to define our own terms, because we're using "sync point" a bit
loosely... I guess there's now 2 separated concepts:
1- the position in the current context that represents the point in the
execution that we will wait on (the uint)
2- an opaque token that globally represents that position, and that can be used
to wait (the GLbyte array)

I think if we put a name on each of them, this spec would read a little better.
We can rename the entrypoints in accordance too. Could be "execution point" (for
1) and "sync token" (for 2), but I'm not married to these names.

[David Yen, 2015/09/08 22:54:14]

Maybe just use "fence sync" and "sync object" to match how the ARB_sync spec is
written? So it would be InsertFenceSyncCHROMIUM, GenSyncObjectCHROMIUM, and
WaitSyncObjectCHROMIUM.

+    sync point acts as a fence, which is signaled when previous commands have been submitted to the server, or when the context is destroyed,

[piman, 2015/09/08 22:19:47]

nit: wrapping at 80 columns

[David Yen, 2015/09/08 22:54:14]

Done.

+    whichever happens first. The sync point name is only visible for the
+    current context. Before the returned sync point is waited upon, the command
+    must be flushed and converted to a sync point object using
+    GenSyncPointCHROMIUM. The opaque object returned from GenSyncPointCHROMIUM
+    is shared between all contexts.
 
     The command
 
-        void WaitSyncPointCHROMIUM(uint sync_point)
+        void GenSyncPointCHROMIUM (uint insertion, GLbyte *sync_point)
+
+    converts <insertion> which is only visible to the current context to a
+    sync point opaque object which is global between all contexts on the same
+    server. The <insertion> command must be flushed before this function may be
+    called, otherwise an INVALID_OPERATION error is generated. <sync_point> may
+    be passed to any other context on the same server to be waited upon.
+
+    <sync_point> returns a GL_SYNC_POINT_SIZE_CHROMIUM byte sized name

[piman, 2015/09/08 22:19:47]

nit: .

[David Yen, 2015/09/08 22:54:14]

Done.

+
+    The command
+
+        void WaitSyncPointCHROMIUM (GLbyte *sync_point)
 
     causes the current context to stop submitting commands until the specified
     sync point becomes signaled. This is implemented as a server-side wait.
-    <sync_point> is the name of the sync point to wait for. If <sync_point>
-    isn't a valid sync point returned by InsertSyncPointCHROMIUM, or if the sync
-    point has already been deleted, the command is equivalent to a no-op and no
-    error is generated.
+    <sync_point> is the name of the sync point to wait for that was generated
+    by GenSyncPointCHROMIUM. If <sync_point> isn't a valid sync point
+    returned by GenSyncPointCHROMIUM, the command is equivalent to a no-op
+    and no error is generated.
+
+New Tokens
+
+    The size of a mailbox name in bytes.
+
+        GL_SYNC_POINT_SIZE_CHROMIUM                         12
 
 Errors
 
-    None.
+    INVALID_VALUE is generated if the <insertion> parameter of
+    GenSyncPointCHROMIUM is not a valid local sync point insertion name.
+
+    INVALID_OPERATION is generated if the <insertion> parameter of
+    GenSyncPointCHROMIUM has not been flushed to the server.
 
 New State
 
     None.
 
 Revision History
 
     2/25/2013    Documented the extension
+
+    9/8/2015     Added CHROMIUMsync, WaitSyncPointCHROMIUM