How to visualize data from google protocol buffer?

One GUI I just came across is protobufeditor -- it seems pretty powerful for browsing generic data. It is written in Java, so one cannot easily use/extend it from C++. (And it is not particularly polished at this point, e.g., one needs to maximize the main window to get a semi-useful layout of the sub-windows.) So this is a rather temporary solution.

Wireshark has a protobuf plugin that lets you visualize the contents of protobuf messages. I'd also dig in to the DebugString() in google/protobuf/message.h or message_lite.h (I forget which off the top of my head) and see if you can easily dress that up for presentation to a user.

http://code.google.com/p/protobuf-wireshark/