artemp/mapnik — Issue #583: Processing of multiple symbolizers in SVG
Author: artemp
Created: 2011-10-11 16:26:56+00:00
State: open
Labels: Core_Library

Agg and cairo renderers process each symbolizer individually, because their corresponding libraries handle the polygon filling and line stroking operations separately.

However, in SVG, the fill color and the attributes of the line in a polygon or path are specified together: .

To be able to generate such output, information from both polygon and line symbolizers has to be available. So SVG renderer needs to process more than one symbolizer at a time.

All renderers are subclasses of feature_style_processor. Feature_style_processor implements a dispatch mechanism to process each symbolizer of a rule sequentially, so there is no way to use information from two symbolizers and relate that information to a given feature.

What is the proper way to modify feature_style_processor to deal with this situation?