ipython/ipython — pull request #2138 by tkf (2012-07-14 20:49:10+00:00)
Title: Use breqn.sty in dvipng backend if possible

This PR improves dvipng backend for latex_to_png function by using [breqn](http://www.ctan.org/pkg/breqn) when it is installed.

breqn automatically breaks equation so you can view very long equation in Qt console, like this:

However, this patch is not complete yet because sympyprinting unconditionally use matplotlib backend for non-display equations. I think configuration to choose matplotlib/dvipng backend is needed. What do you think? Also, if having configuration is a right choice, where should I put configuration class? I can't find any IPython extension using its own configuration.

To check how new latex_to_png works, you can put the following line in `IPython/lib/latextools.py`, just after the definition of `print_display_png`.

```python
print_png = print_display_png
```