Mac OS X Leopard - ARCAism

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CHAPTER 25 MAC OS X DEVELOPMENT: THE TOOLS
car would then play back your drive exactly as it occurred. The mechanic could rewind and fast
forward, or even pause and disassemble parts of the car frozen in time at the exact moment of
the problem.
Once the problem is diagnosed and fixed, it could be played back to confirm that the problem
no longer occurs. This is exactly what Instruments does for your applications. Whether
you’re the programmer who wrote the application, or a user who finds a bug in it, Instruments
is very exciting.
Under the hood, Instruments runs on DTrace, an OpenSolaris project included in Leopard
that provides probes in the very lowest levels of the machine. Thousands of these probes sit idle,
causing no performance drain, waiting for the moment they are activated by masters of the
arcane arts wishing to see the details of any process.
While using Instruments fortunately doesn’t require grimoires, sacrifices, or learning the D
scripting language, this open source engine means that the aforementioned arcane masters can
create new instruments and share them with the community. As a further testament to the power
of Instruments, several developer tools in Apple’s toolbox have been replaced with Instruments
templates.
Quartz Composer
Another tool that seems to have been designed by musicians, Quartz Composer is a visual environment
for creating code-free graphical programs using a patch metaphor that should be most
familiar to aficionados of the electric guitar. Instead of functions, Quartz Composer uses modules
called patches. Patches take one or more inputs, change them in some way, and produce one
or more outputs.
Patches are connected by dragging and dropping virtual cables, not unlike Interface Builder.
By connecting the different inputs and outputs, users can create complex compositions, as shown
in Figure 25-22. Quartz Composer compositions can be rolled into freestanding programs, used
as screen savers, or incorporated into other, larger programs. It’s also just a fun way to spend an
afternoon.
Figure 25-22. Visual programming in Quartz Composer