Move a lot of processing into a common process_group_symbolizer function.
Also, extract column collection out of process_group_symbolizer function.
This will reduce duplication needed for other renderers.
Segfault was due to `glyph_position` structs keeping a pointer to
`glyph_info` objects which went out of scope at a different time.
The (rather ugly) fix for the moment is to copy that information
into the thunk object.
Create a group_symbolizer_helper for group placments, and extract some code from
text_symbolizer_helper into a base class to share with group_symbolizer_helper.
Also, move tolerance_iterator into its own header file. Use helper in
process_group_symbolizer to find placement positions.
This renders the saved information from previous calls to the
bounding box extraction code, offset by some amount which should
be determined from running the `placement_finder`. Note that this
doesn't implement that bit, just the rendering.
This is done by creating a fake 'virtual' environment at a fake
point and running the symbolizer render code. The actual render
is saved in a thunk for after the group layout has been done.
This includes XML parsing of group symbolizer and related objects and
process_group_symbolizer method in the AGG renderer. This also includes
code to collect group symbolizer indexed columns, create sub features,
and match them to group rules.
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.
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.
- 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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