[Qgis-developer] new generation symbology

[Martin Dobias]

Hi all

today I've decided to make a first public release of symbology-ng
plugin which is meant as a prototype for new generation symbology for
vector layer. I've chosen python because of faster development and
ability to deploy it more easily to potential testers. Later, I'd like
to integrate it to QGIS and deprecate the original rendering code. You
can install the plugin from my sandbox:
http://mapserver.sk/~wonder/qgis/plugins-sandbox.xml

What are the main highlights:
- compose symbols from one or more symbol layers
- load and store symbols (and other items) from/to a "style" file
- override order in which symbol layers are drawn for high-quality
output (done in multiple rendering passes)
- color ramps (gradient or random colors from some part of color space)
- use custom symbols and color ramps when generating categories for a renderer
- new symbol types, e.g. marker line - polyline composed from markers
- lock symbol layer's color so it doesn't get changed when applying
color on the whole symbol
- modual architecture for symbol layers

When you load the plugin, you'll get two new buttons in a toolbar:
1. one that opens a new window with currently selected vector layer
rendered in it (with current extent). in that window you can also
change renderer and symbology settings (although graduated symbol
renderer is missing GUI so far and categorized symbol renderer only
allows you to add all categories)
2. the other button opens style manager

The rendering is slower than with current rendering in QGIS, but
that's caused by the dynamic nature of the language and missing
optimizations. There are some features which are not yet available in
GUI. There are also some missing features, see TODO file.

I would be glad to hear some feedback from you!

Martin