This involved making the freetype engine stack allocated and
accessible via a `shared_ptr` because `FT_Face` elements stored
in it are referenced from cairo structures which persist beyond
the lifetime of the `cairo_renderer` object.
Hopefully this can be resolved in a future commit.
All the grid visual tests pass.
One small issue is that in the grid line pattern symbolizer it
constructs a 'fake' line symbolizer to re-use code (as the grid
renderer cares nothing for patterns), but doesn't pass the
offset parameter to it. The tests currently require this
behaviour, but they should probably be changed as it seems
incorrect.
- Implementation by @herm for GSOC 2012 (http://mapnik.org/news/2012/10/06/gsoc2012-status9/)
- C++11 port, improvements, optimizations by @artemp
- Testing and integration with master by @springmeyer
- Thank you to all the support from @behdad along the way
- Thanks for help testing @toton6868, @stephankn, @nirvn, @mfrasca, @simonsonc and many others
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