What C++ open-source projects have good and clean code to learn from? 
What `C++` open-source projects have good and clean code? I would like to go through it and learn the design and implementation tricks used there.

There was a similar question about C code [here][1], but I would be specifically interested in `C++` projects, especially in ones that use modern programming approaches and have modular but not bloated overall structure and object-oriented design.

I know I could look at code in [Project Euler][2] or [Topcoder][3], but I'd like to see the architecture and design of a whole nicely-sized, but not too large project (say, up to 50 or so classes). 

There was also [this][4] question, but no one mentioned `C++` projects.

And one more thing: I know the best way to learn is actually writing code yourself. But I'm already doing that. A lot.

  [1]: http://stackoverflow.com/questions/144568/learn-c-from-open-source-code
  [2]: http://projecteuler.net/
  [3]: http://www.topcoder.com/
  [4]: http://stackoverflow.com/questions/27793/well-written-open-source-projects-for-learning
What C++ open-source projects have good and clean code to learn from? 
===

What `C++` open-source projects have good and clean code? I would like to go through it and learn the design and implementation tricks used there.

There was a similar question about C code [here][1], but I would be specifically interested in `C++` projects, especially in ones that use modern programming approaches and have modular but not bloated overall structure and object-oriented design.

I know I could look at code in [Project Euler][2] or [Topcoder][3], but I'd like to see the architecture and design of a whole nicely-sized, but not too large project (say, up to 50 or so classes). 

There was also [this][4] question, but no one mentioned `C++` projects.

And one more thing: I know the best way to learn is actually writing code yourself. But I'm already doing that. A lot.

  [1]: http://stackoverflow.com/questions/144568/learn-c-from-open-source-code
  [2]: http://projecteuler.net/
  [3]: http://www.topcoder.com/
  [4]: http://stackoverflow.com/questions/27793/well-written-open-source-projects-for-learning