Create PDFs with CoreGraphics and Python

I've just stumbled onto one of the neatest features of Mac OS X for Python developers. I haven't seen any mention of this before, but then I don't think many folk spent an idle Saturday morning catching up on the news and idly clicking away inside the Developer folder.

It turns out I have a couple of disk space issues (my policy of doing integral laptop backups leads to a lot of redundant files), so I was looking for a way to visualize disk usage in Mac OS X. One of the most intuitive applications I have for that (under Windows) is SpaceMonger, a very neat utility that gives me a graphical overview of disk usage using a treemap-like approach. TkDu provides mostly the same experience under X11, but I wanted something that didn't require X11 to run (or Tk, for that matter).

Despite not going in for Objective-C and having studiously avoided coding in Cocoa so far (it's not a portable enough skill to invest my time in), I started looking around for OpenGL samples. Nevertheless, I had a stroke of luck: while hunting through the Developer/Examples folder, I came upon Quartz/Python and the mega-cool CoreGraphics bindings for Python, which enable you to create PDFs with nothing more than the Panther-bundled Python and a little ingenuity:

#  Simple python example to draw a circle

from CoreGraphics import *
import math   # for pi

pageRect = CGRectMake (0, 0, 612, 792)   #  landscape
c = CGPDFContextCreateWithFilename ("circle.pdf", pageRect)
c.beginPage (pageRect)

Being an old Postscript buff, the Quartz primitives are very familiar to me, and after reading through the great sample (which renders a contact sheet of an image folder), I felt confident enough to start hacking my own version of TkDu with PDF output.

After all, I don't really need a full-blown GUI app - running a simple script and getting Preview to pop up with the file map is enough, and I get Preview's built in zooming and panning functionality for free. Sure, it's not interactive, but I'd rather wait until Mono becomes easier to use in Mac OS X and I can hack together a more portable tool.

Code will be up in the CVS section once I can get it to work properly (the coordinate system is bit screwed up right now, and there are a few issues with fonts). In the meantime, I suggest you spread the word amongst the Mac OS X Python buffs - there are a lot more Python bindings in there.

Mono on X

I've taken a bit more interest in Mono and DotGNU lately. There's been a lot of both dumb and insightful press coverage on it, but MonoDevelop and the push for getting it to play well with Gnome are turning Mono into a more palpable (and relevant) technology.

Of course getting it to run "properly" (i.e., easily) in Mac OS X will entail Xcode integration, but that seems to be in the works. I can't find any follow-up on this, though - and I guess it will be a while until we can get a nice Mac OS X installer (or a set of Fink packages) to make it easier to get Mono running on Mac OS X.

Odds and Ends

I've picked up my Bayesian RSS classifier project again, and at this point I've put portions of it up on CVS. I'm testing the classifier with a custom harness and trying to figure out a decent UI for it at the same time, and found quite a few usability issues (for instance, making it easy to train the classifier on specific RSS entries with a single click, or delivering an acceptable experience on a PDA). It's going to take a while...