Gtk3 Update and Style Normalization

Hello,

I've fixed one of the cairo painting files since it used Gtk2. 

Also, I noticed the style to be random in some places. I've proposed some changes so it's more consistent.

Personally, I prefer:
```
    method( arg1, arg2 )
```
to
```
     method(art1, arg2)
```

I consider it to be more readable. This said, I've left out my preference to be consistent with the rest of your examples.

Feel free to leave the style normalization out of the pull request if you don't like it.