If you were an OS 9 fiddler, tweaker, or deviant, there was one piece of software you simply had to have: ResEdit, Apple’s venerable, unsupported, use-at-your-own risk utility. ResEdit is no longer applicable under OS X, but package editing is.
In earlier versions of the Mac OS, files could have data forks and resource forks. The data fork was the gooey inside, and the resource fork was the fluffy outside — whether it be image thumbnails, saved editing data from applications like BBEdit, or application widgets, like window layouts, user interface images, and so forth. With Apple’s ResEdit, you could easily access this resource fork and change the fluff — it wasn’t easily possible to change the coding of an application, but it was certainly mindless to change interface elements.
In OS X, with its grounding in the BSD operating system, resource
forks are rarely used for applications, effectively making ResEdit
useless. Instead, we’ve got packages or, less
jargony, files that end in
.app files spread
all over your OS X system already — you just may not know it.
Take, for instance, Apple’s popular
Mail program. It sits
innocently in your
Applications folder, acting
as if it were a single file. Instead, it’s really
is hidden from view (you can confirm its existence by examining the
Get Info properties).
The magic of these
.app files is that
they’re really a special kind of
folder called a package; they contain
a good portion of the same fluff available in an OS 9
application’s resource fork. Even better, you
don’t need an extra utility like ResEdit to start
fiddling; simply Control-click on a file you know is an
.app and choose Show Package Contents, as shown
in Figure 1-21.
Once inside the package Contents folder,
you’ll see a subfolder called
Resources (see Figure 1-22). If
you needed yet another hint that this is similar to ResEdit hacking,
then this naming choice is it. In the case of
Apple’s Mail, we can see a decent number of image
files, representative of various visual elements you see during
normal use of Mail, as well as a few
The .tiff and
.icns files are obvious; modify them in your
preferred graphic editor, restart Mail, and you’ll
see your changes.
.plist files are the
equivalent of preferences; there are usually frontends to these
settings via the program itself (not always though — in
Mail’s case, you can edit
urlPrefixes.plist to add more clickable bits of
text in mail messages, or
Colors.plist to edit
two more levels of quote coloring).
English.lproj for English-speaking
users, are where you can find some user-interface aspects of the
program in question. You won’t see these for every
package you open (like iTunes), but in the case of Mail, you can go
nuts editing warning messages, like this one in
Prefs.strings (perhaps to the more ferocious
“Ya Screwed Up, Idiot!”):
/* Title of panel shown when the user tries to enter an empty hostname for an account */ "INVALID_SMTP_HOST_TITLE" = "Invalid SMTP Hostname";
On the other hand, if you know your way around
Apple’s Interface Builder (available if you have
the Apple Developer Tools [Hack #55] installed), you can open up one
of the many
.nib files and further tweak display
As with the typical warnings when using ResEdit, be sure to make a backup before doing anything more than exploring (and exploring is when the best discoveries are made, like the ability to peel the annoying chrome [Hack #47] from a shiny iApp, add new boards and pieces to Chess, or change the default search engine in Internet Explorer).