There's a lot of code common between symbolizers which do things
like layout, setup, etc... So it seems sensible to extract the
common operations & loops into a single place which is
independent of the actual renderer.
I've started doing this with C++11 lambdas, although that might
not be the best implementation long term. Should be easy enough
to change, though.
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.
The idea here is that much of the code in the renderers and the
various `process_*` rendering methods is shared, but this sharing
is obfuscated by the lack of sharing of renderer fields and
methods.
This is the first step in trying to factor out commonalities in
order to simplify the implementation of the renderers and make
them easier to understand and modify.
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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