Build vector tile protocol buffers when rendering
Initialize graphics from a hook rather than directly.
Produce an empty vector file, without any actual drawing.
Wrap tile object so we can have additional state.
Move clipping to its own file.
Hook up to line clipping
Start writing a feature to the output
Start writing out drawing commands.
Do the zig-zag encoding.
Copy zlib compression boilerplate from mapnik-vector-tile
It actually draws something!
Fix stupid bugs. Now it actually draws the right lines!
Accumulate lines into a buffer instead of outputting directly.
Don't save any lines with identical origin and destination.

It draws all wrong if you have any like that.
Chain together any lines that can be chained together.
Turn off chaining.

Seems to make the tiles bigger, not smaller, by losing locality
for relative movements.
Give the layer a more sensible name.
Produce a points layer too.
Make tiny polygons instead of points.

It is much faster and smaller because they can all go in the
same feature instead of needing a new feature for each one.
Use the old libpng API so it will work on pre-1.6 installations.

The simplified API is so much nicer, but 1.2 is still extremely common.