Drawing Area issues ( continued, with example )

[Daniel Kasak <d j kasak dk gmail com>]

Hi again everyone.

I've cut down my app to a "relatively small" example which doesn't
need a database connection or loads of other stuff. It's still 400+
lines ( with lots of whitespace ). I know it's asking a lot, but if
someone can figure out what I'm doing wrong, I'd be very grateful ...

If you hit the 'graph 1 date' button, you'll get a perfectly working
graph ( hit it multiple times to cycle through the 4 series I've added
to the example data ). If you hit the 'graph 4 dates' button, you'll
see the bug I'm trying to fix. The 'render text dots' checkbutton
activates rendering of some dots via Pango in approximately the same
areas as the graph series should be rendered. The dot rendering uses
the same cairo context that I'm using for rendering the graph series.
I would expect that if I'm doing something horribly wrong with my
cairo contexts, the *dots* would also render in the wrong place ...
but that's not happening.

Help!

Fully self-contained example:
http://tesla.duckdns.org/downloads/drawing_area.tar.bz2

Dan