PPAPI: Synchronous postMessage proposal #1

ppapi/c/ppb_messaging.h

Index: ppapi/c/ppb_messaging.h
diff --git a/ppapi/c/ppb_messaging.h b/ppapi/c/ppb_messaging.h
index 06e31205167eb495e54c51ebd5a9bafcb6c7731f..f80a3f1d1767f8cff3b058da403d727ecdc25c6f 100644
--- a/ppapi/c/ppb_messaging.h
+++ b/ppapi/c/ppb_messaging.h
@@ -3,19 +3,21 @@
  * found in the LICENSE file.
  */
 
-/* From ppb_messaging.idl modified Wed Jun  5 10:32:59 2013. */
+/* From ppb_messaging.idl modified Mon Apr 28 13:06:18 2014. */
 
 #ifndef PPAPI_C_PPB_MESSAGING_H_
 #define PPAPI_C_PPB_MESSAGING_H_
 
 #include "ppapi/c/pp_bool.h"
+#include "ppapi/c/pp_completion_callback.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_macros.h"
 #include "ppapi/c/pp_stdint.h"
 #include "ppapi/c/pp_var.h"
 
 #define PPB_MESSAGING_INTERFACE_1_0 "PPB_Messaging;1.0"
-#define PPB_MESSAGING_INTERFACE PPB_MESSAGING_INTERFACE_1_0
+#define PPB_MESSAGING_INTERFACE_1_1 "PPB_Messaging;1.1"
+#define PPB_MESSAGING_INTERFACE PPB_MESSAGING_INTERFACE_1_1
 
 /**
  * @file
@@ -34,7 +36,7 @@
  * and is related to sending messages to JavaScript message event listeners on
  * the DOM element associated with specific module instance.
  */
-struct PPB_Messaging_1_0 {
+struct PPB_Messaging_1_1 {
   /**
    * PostMessage() asynchronously invokes any listeners for message events on
    * the DOM element for the given module instance. A call to PostMessage()
@@ -96,9 +98,60 @@ struct PPB_Messaging_1_0 {
    * The browser will pop-up an alert saying "Hello world!"
    */
   void (*PostMessage)(PP_Instance instance, struct PP_Var message);
+  /**
+   *  Call this to prepare to receive a blocking message from JavaScript.
+   *  When JavaScript invokes postMessageAndAwaitResponse(), the callback will
+   *  be invoked (or, if a blocking completion callback was used,
+   *  WaitForBlockingMessage will return).
+   *
+   *  When the call completes, |message| will be a PP_Var containing a copy of
+   *  the data passed from JavaScript to postMessageAndAwaitResponse().
+   *
+   *  Upon receipt of the callback, the plugin must respond to the plugin by
+   *  calling RespondToBlockingMessage. The JavaScript invocation of
+   *  postMessageAndAwaitResponse will not return until the response is
+   *  received, so it is important to respond quickly.
+   *
+   *  Invocations of WaitForBlockingMessage will fail if JavaScript is still
+   *  awaiting a response to a prior invocation of the callback. Therefore, the
+   *  plugin must always call RespondToBlockingMessage before calling
+   *  WaitForBlockingMessage again.
+   *
+   *  Example usage:
+   *  void thread_func() {
+   *    while (!ShouldQuit()) {
+   *      PP_Var param = PP_MakeUndefined();
+   *      WaitForBlockingMessage(pp_instance, &param,
+   *                             PP_BlockUntilComplete());
+   *      PP_Var response = ComputeSomething(param);
+   *      RespondToBlockingMessage(pp_instance, response);
+   *      var_if.Release(param);
+   *      var_if.Release(response);
+   *    }
+   *  }
+   *
+   *  WaitForBlockingMessage will only work if called from a background thread.
+   *  If it is invoked from the main Pepper thread, the result will be
+   *  PP_ERROR_WRONG_THREAD.
+   */
+  int32_t (*WaitForBlockingMessage)(PP_Instance instance,
+                                    struct PP_Var* message,
+                                    struct PP_CompletionCallback callback);
+  /**
+   *  Send a response to JavaScript. This only makes sense if JavaScript is
+   *  currently blocked on postMessagAndAwaitResponse. JavaScript's
+   *  postMessageAndAwaitResponse function will return a JavaScript value
+   *  representing a copy of |response|.
+   */
+  void (*RespondToBlockingMessage)(PP_Instance instance,
+                                   struct PP_Var response);
 };
 
-typedef struct PPB_Messaging_1_0 PPB_Messaging;
+typedef struct PPB_Messaging_1_1 PPB_Messaging;
+
+struct PPB_Messaging_1_0 {
+  void (*PostMessage)(PP_Instance instance, struct PP_Var message);
+};
 /**
  * @}
  */