A blog where I will write mostly about programming in Cocoa and CoreMIDI, and experiences from my ports of Emacs and XEmacs to the Mac OS.

MusicKit

Friday September 26, 2003

I spent a little time today playing with MusicKit. Unfortunately, after the lengthy installation process, only a few applications and examples built successfully, and among these, fewer worked correctly. Those that seemed to work were EnvelopeEd, PatchCord, MidiFilePlayback, MidiLoop, and MidiRecord.

CoreMIDI, OMS, and FreeMIDI just aren't very good API's for writing MIDI programs. I'm studying the MusicKit API to see if it is perhaps a bit nicer.

[Later that evening...] I played with PyObjC. Looks like quite an amazing piece of software! It takes frameworks and makes them available to Python programs. Now there seem to be three ways to call the MIDI library I'll write from Python:

• write it in C or C++ and generate the interface using SWIG,
  
• write it in Objective C, package it as a framework, and use the PyObjC bridge, or
  
• write it in C, C++, or Objective C and also write a wrapper for it (in C) using the Python/C API.
  

SWIG and Python Distutils

Thursday September 25, 2003

Today I learned to use the Python distutils to build dynamically loaded modules. A module is written in C and its attributes are described in a file setup.py. Distutils then takes care of building it. It'll even package the module for distribution in various forms.

Then I played with SWIG a little. It takes a C header file (basically) and generates wrappers for functions in it so that they can be called from different languages. The documentation doesn't explain how Python modules should be generated on Mac OS X. Running the distutils build command with the --dry-run option shows what the compiler and linker options look like.

Afterwards I found out that distutils is clever enough to call SWIG if source files have the .i suffix. So the setup.py file below will correctly build a Python module from the files example.i and example.c. Quite painless.

import distutils
from distutils.core import setup, Extension

setup(name = "Example in SWIG tutorial",
      version = "1.0",
      ext_modules = [Extension("_example", ["example.i","example.c"])])

Turtle Graphics with Embedded Python

Wednesday September 24, 2003

I embedded Python instead of Guile in the turtle graphics toy, resulting in this PB project. To build it you need to first build and install Python 2.3 as a framework as described in Python-2.3/Mac/OSX/README. The tortoise (static) module exports the functions reset, pendown, penup, move, and turn. To play with it, type Python statements into the text view and click “Evaluate”. Try this:

import tortoise

def move_and_turn(angle):
    tortoise.move(100)
    tortoise.turn(angle)

for i in range(9):
    move_and_turn(80)

Python Spam Cleaner Script

Monday September 22, 2003

OK, this spam thing is getting out of hand. So here is a Python script for fetching message headers from a POP3 server and offering to delete them if they satisfy certain criteria. Only headers are fetch so this is faster than checking mail using a regular mail client. Since the worm permutates buzzwords in the subject line, currently only multipart/mixed and multipart/alternative messages in certain size ranges are offered for deletion. This seems to catch over 80% of the spam messages.

Meanwhile I should finish reading the Python tutorial today and start looking at embedding Python in a Cocoa program.

Damned E-mail Worm

Sunday September 21, 2003

Thanks to the worm, I now realize how many people have my address on their computers :-). What baffles me is how careless my friends can be in preventing their computers from being attack. Mind you, some of them are people knowledgeable in computer science, like CS professors!

If this thing continues, it'll be quite easy to write a tool to automatically screen the messages at my POP account before fetching them. In the mean time, I'm using a modified version of this little Python script to do that manually.

To edit the script in Emacs, I used this Python mode.

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