Web MIDI API back-end (work-in-progress)

content/common/media/media_param_traits.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_COMMON_MEDIA_MEDIA_PARAM_TRAITS_H_
 #define CONTENT_COMMON_MEDIA_MEDIA_PARAM_TRAITS_H_
 
 #include "content/common/content_export.h"
 #include "ipc/ipc_message.h"
 #include "ipc/ipc_param_traits.h"
 
 namespace media {
 class AudioParameters;
+class MIDIPortInfoList;
 struct VideoCaptureParams;
 }
 
 namespace IPC {
 
 template <>
 struct CONTENT_EXPORT ParamTraits<media::AudioParameters> {
   typedef media::AudioParameters param_type;
   static void Write(Message* m, const param_type& p);
   static bool Read(const Message* m, PickleIterator* iter, param_type* r);
   static void Log(const param_type& p, std::string* l);
 };
 
 template <>
 struct CONTENT_EXPORT ParamTraits<media::VideoCaptureParams> {
   typedef media::VideoCaptureParams param_type;
   static void Write(Message* m, const param_type& p);
   static bool Read(const Message* m, PickleIterator* iter, param_type* r);
   static void Log(const param_type& p, std::string* l);
 };
 
+template <>
+struct CONTENT_EXPORT ParamTraits<media::MIDIPortInfoList> {

[scherkus (not reviewing), 2013/06/12 01:28:47]

hrm... if MIDIPortInfoList was a typedef would you still need all this stuff?

also you may want to take a look at the IPC_STRUCT_TRAITS_XXX() set of macros --
I believe they help autogenerate this kind of code

[Chris Rogers, 2013/06/12 20:34:35]

I took a look at IPC_STRUCT_TRAITS_BEGIN, IPC_STRUCT_TRAITS_MEMBER, etc. which
we use in many places, but couldn't find an example where it's a *list* of
structs that we want to send.  If you can help point me in the right direction
for how to do this for things which are vector<struct>, I'm happy to change it. 
For now, I'm not sure if it's possible, so that's why I wrote the pickling like
it is now.

[scherkus (not reviewing), 2013/06/13 02:05:41]

AFAIK the IPC system knows how to deal with std::vector so you only need to
provide a traits definition for the struct itself.

IPC_STRUCT_TRAITS_BEGIN(media::MIDIPortInfo)
  IPC_STRUCT_TRAITS_MEMBER(...)
IPC_STRUCT_TRAITS_END(media::MIDIPortInfo)

+  typedef media::MIDIPortInfoList param_type;
+  static void Write(Message* m, const param_type& p);
+  static bool Read(const Message* m, PickleIterator* iter, param_type* r);
+  static void Log(const param_type& p, std::string* l);
+};
 
 } // namespace IPC
 
 #endif  // CONTENT_COMMON_MEDIA_MEDIA_PARAM_TRAITS_H_