from __future__ import * 23.2.2004

graphviz on the Mac, LaunchServices

For an excellent example of what it takes to do a great port of UNIX software to OS X, look no further than Glen Low's port of graphviz for OS X. For good reasons to take a look at graphviz, check out John Schull's Weblog, especially entries such as Outline to graphviz.

This port and GUI front-end adds features such as rendering via the native OS X APIs (finally, good fast PDFs!), and it can actually use kqueue on OS X 10.3 to automatically re-render when a file changes!

Not only does at add a slew of cool new features (most of which I didn't mention), but all of the CLI tools are wrapped up in a nice little application bundle; making installation and removal painless, and relocation no longer becomes a problem.

If all OS X with significant UNIX heritage were distributed this way, one might think it would become difficult to add them all to your PATH. Fortunately, that's just not true ¹. Here's a nice little snippet of LaunchServices ² code that will return the full path of an application by name regardless of where it happens to be or if it has moved ³:

#!/usr/bin/python
from LaunchServices.Launch import LSFindApplicationForInfo
from Carbon.CoreFoundation import kCFURLPOSIXPathStyle
# this would normally come from LaunchServices.LaunchServices
# but bgen isn't perfect, and doesn't make this constant a
# four char code.
kLSUnknownCreator = '\x00\x00\x00\x00'

def pathForName(appName):
    """
    Returns the file system path for an application by name.
    NOTE: You should include the suffix, as in "Python.app".
    """
    fsRef, cfURL = LSFindApplicationForInfo(kLSUnknownCreator, None, appName)
    return cfURL.CFURLCopyFileSystemPath(kCFURLPOSIXPathStyle).toPython()

if __name__ == '__main__':
    import sys
    if len(sys.argv) == 1:
        import os
        raise SystemExit, "Usage: %s SomeApplication.app" % (
            os.path.basename(sys.argv[0])
        )
    for appName in sys.argv[1:]:
        print pathForName(appName.decode('utf8')).encode('utf8')

Usage looks like this (note: I use tcsh not bash):

[crack:~/bin] bob% setenv PATH ${PATH}:`./findapp.py GraphViz.app`/Contents/MacOS
[crack:~/bin] bob% rehash
[crack:~/bin] bob% which dot
/Applications/GraphViz/Graphviz.app/Contents/MacOS/dot
[crack:~/bin] bob% dot --help
dot: option -- unrecognized

Usage: dot [-Vv?] [-(GNE)name=val] [-(Tlso)<val>] <dot files>
 -V          - Print version and exit
 -v          - Enable verbose mode 
 -Gname=val  - Set graph attribute 'name' to 'val'
 -Nname=val  - Set node attribute 'name' to 'val'
 -Ename=val  - Set edge attribute 'name' to 'val'
 -Tv         - Set output format to 'v'
 -lv         - Use external library 'v'
 -ofile      - Write output to 'file'
 -q[l]       - Set level of message suppression (=1)
 -s[v]       - Scale input by 'v' (=72)
 -y          - Invert y coordinate in output