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Brief Tutorial on Reverse Engineering Mac OS X
rjw57 writes "There is an article on OSNews I wrote about how the guy behind Desktop Manager goes about reverse engineering APIs from Mac OS X with a brand new example not revealed anywhere else. From the article: 'I am often asked in email how I uncovered the API calls I use in Desktop Manager which are, unfortunately, undocumented. This article aims to give a little insight into the techniques I use to reverse engineer Mac OS X in order to provide extra functionality to users and extra information to third-party developers. In this article all the utilities I use are a standard part of Mac OS X's developer tools which are freely available.'"
All credit to the author; it looks like quite a feat of reverse engineering and some genius coding has probably gone into it. Apologies for the subsequent inflammatory opinion.
... try having a real discussion instead).
However, Apple have already come up with a perfect way of handling large groups of windows on one screen; it's called expose. I used to use virtual desktops on Linux, which was adequate, but when I got a Mac I settled in nicely with Expose; OS X has a near perfect user interface designed by actual HID experts. The only reason I can think of for using virtual desktops is if you're some kind of Linux zealot.
(Don't mod me down just because you're an anti-Mac zealot mod
Great example of apples practice of breaking API's leaving developers out of the loop
It's an undocumented, unsupported API; that's what the article is about. What broken APIs were you thinking of? Carbon took over most of the OS 9 ones (apart from some clearly documented exceptions).
If you had read the article you might actually have had something useful to say.
It's an undocumented API.
That's one of the many reasons why some APIs are left undocumented: because they are expected to be unstable.
Can't really blame Apple on this one. They didn't publish the API, and changed it in Tiger to a more flexible three-part solution. Eventually they may decide the design's a good one and publish the API.
Until then, use it at your own risk.
In this example, Apple broke undocumented APIs. Anyone writing or using an application that takes advantage of undocumented APIs should be prepared to discover that they've been changed, moved, or deleted entirely.
The APIs that DesktopManager uses were probably left undocumented precisely because Apple knew they were going to be subject to change.
Apple is good, and we are going to talk to talk about it.
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I myself have found that by really learning how to manage windows the "apple way" I don't really feel the need to use virtual desktops much (I used to use DesktopManager).
For me, this means using Hide (Command-H), Swich app (Alt-Tab), Focus on window (active) or next window (a custom key binding like Alt-Tab), and Expose.
But that doesn't mean there isn't a place for virtual desktops.
One thing that expose relies on is that the conceptual groupings of "All app windows" and "All of this apps windows" are all you need. The problem is if you have a large number of similar looking windows from different applications it can be difficult to manage even with Expose.
Virtual desktops can give you custom Expose groups - which can narrow the search for a particular window. This can be useful if you are working on several complex tasks that use multiple windows from multiple apps (each task can get its own desktop), and also have a bunch of side apps - like your calendar, email, instant messenger etc.
So Expose solves the window management problem to an extent, but it can be combined with virtual desktops when things become even more complex.
The story you linked to is about copyright infringement, not reverse engineering. It has nothing to do with TFA. Apple is not encrypting their undocumented code, so it has nothing to do with the DMCA. Reverse engineering is not necessarily banned by the DMCA; in fact, reverse engineering for interoperability is specifically exempt from it.
English is easier said than done.
I think people mean: this is a great example a post by someone who doesn't read the article. :-)
Personally, I'm all for adding cool new features to Mac OS. They will likely document them at some point.
I don't know, but it works for me.
So now we find out that Apple has used - and is using - undocumented API calls.
Sounds like something Microsoft would pull.
Oh, wait, this is Slashdot. I forgot.
Well, then Apple's just trying to protect its intellectual property. No harm.
I don't think there's anything wrong with Microsoft having undocumented (call them secret if you want) APIs. You're making the "all Slashdot posters share the same opinion" mistake.
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all API's are documented, well, API's that are written in a company the size of apple anyways and in any other software project done by pro's(hopefully anyways).
they're just some that some committee or workgroup decided that they shouldn't be used.. all closed os's have those.. hell, I'm frustrated at the moment at symbian because of precisely this(well, nokia to be more specific but anyways..). it bugs the hell out of me that there's a bunch of things in there that aren't open.. but that are in and usable and you need to use them for certain projects(and the api, including them, changes between versions anyways).
everything is subject to change. just that when it's undocumented you'll never know about it untill it just doesn't work anymore.
world was created 5 seconds before this post as it is.
So now we find out that Apple has used - and is using - undocumented API calls.
Um, no Apple has no applications that use the virtual desktop APIs to compete unfairly with third party apps. In fact Apple has no competing application in this area at all, and two of the three applications that DO exist are open source.
On Solaris there is a command truss that is the king of all truss-like commands. Unlike strace, ktrace, and BSD truss this tool can print a trace of all function calls made by an application as it runs (among many other useful things). Does anyone here know of an analogous tool for MacOS X? If not I wonder if an awk/perl script munging the output of nm to generate tracepoints for gdb where each trace point creates a new tracepoint at the instruction where the function call returns, prints out the funtion name and the contents of r2-r10 or so, then continues on or something like this would be something someone has already written.
"He who would learn astronomy, and other recondite arts, let him go elsewhere. " -- John Calvin, commenting on Genesis 1
Actually, these are undocumented SPIs, Systems Programming Interfaces. SPIs exist in many layered systems, and are intended to provide functionality used to implement higher level mechanisms.
In Mac OS X, for example, the CGS SPIs provide functionality used by the Carbon, Cocoa, and Java environments. (You didn't really think Carbon and Cocoa somehow each implemented their own window systems, did you?) The SPIs are private because, simply, the functionality they provide is pretty raw, low level stuff. Using the private SPIs behind the back of an application could readily lead ti inconsistent state in an application, leading to exciting events such as the Spontaneous Program Logic Application Termination (SPLAT).
"Documentation' for some of these really low level SPIs may consist of sophisticated mechanisms along the lines of "Hey! Andrew! How's this supposed to work?" (Yes, everything should be documented, and preferably folded into a CASE system that won't let you compile anything until the documentation is written. After all, that's how the LINUX kernel is managed, right?)
No doubt an Appleista will be along in due course to make clear the path to enlightenment.
You called?
The answer to your difficulty is obvious: follow the money. What strategic advantage does Apple gain by not publicly documenting these APIs? A corner on the windows management market? I'm sure is worth a whole lot because you can see how much Apple charges for it at the Apple Store. Oh, wait, you can't, cause there is no such separate competing product that Apple profits by leveraging their OS.
vs. Windows, where, let's see, they made a substantial amount of their $50 Billion on by selling Office--which required that they kill their competition in Office applications.
"But what of IE?", I hear you plaintively cry. "Doesn't Microsoft give that away for free?" Certainly. But their clear strategy was to use the product to own the web, and IE was the platform to do it.
When Apple sells a virtual desktop management tool, besides the OS, and doesn't document the APIs, you'd have an argument. For example, I imagine QT has access to things that WMP doesn't, but proving that is an exercise for the reader. As it is, you're just trolling. Speaking of simplistic arguments.
--
$tar -xvf
...what I really want is to be able to hit (for example) control-alt-F1 and get a full-screen command line. Every so often I've got a lot of crap open and I just want nothing but a big, empty, command window.
Dear Slashdot: next time you want to mess with the site, add a rich-text editor for comments.
I think the difference is this: does Apple use undocumented API's to purposely cripple, outright break, or unfairly compete with third party vendors. The list is long when dealing with microsoft, all the way back to dr. dos. if Apple did this, say a photo-manipulation app that competed with say, adobe, then there'd be room to bitch if if they used undocumented and secret API's to speed up rendering. or perhaps they have a secret network protocol that is used to connect os x clients to os x servers only. it sounds like their desktop features are designed to compete with windows, which makes the API's not relevant. and unlike windows, there really is a mac way to do things, which apple really wants to enforce. they don't care if someone is screwing around with xcode and comes up with some neato little $5 shareware app, they are concerned with big commercial apps and they want them to do things a certain way, the mac experience. like it or not, that's what they do. if it's to enforce application uniformity than that's hardly a sin.
My problem? I was perfectly gruntled, until some numbnuts came by and dissed me.
The functions in question are not API at all, by definition. Since they are explicitly not supported, they are not part of the Application Program Interface, and not documented (of course).
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
I know that it's fun to pick apart the framework code, make guesses as to what it's doing and how, and write code that exploits it in some way, but don't, don't, don't write a commercial product that depends on what you discover by this kind of spelunking, unless you are fully prepared to deal with the consequences of it breaking at any software update.
If your users call Apple because your program broke, Applecare will tell them to talk to you about it. If you ask Apple for help with an undocumented API, your request will be declined.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
Try reading the DMCA.
Reverse Engineering for interoperability is explicitly permitted.
I needed more workspace, so I went multihead. Some apps lend themselves well to virts - web browsing, email, a pile of xterms... but when you're running something like photoshop and you need more "room to maneuver". adding extra heads is the way to go.
:-(
:-|
I seem to be the only OS X user that neither uses no likes Expose much. Part of it's the fact that a few apps I use bind to F11-13, though my BIG gripe is that F14-F16 ARE NOT MAPPING OPTIONS. Why can't I put the shortcuts for Expose onto the three keys that I NEVER use for ANYTHING?
That aside, I've noticed that virts are something the "I used to use freenix but the desktop sucks so I switched" crowd complains about, as well as sloppy focus and the fact that portables have one button trackpads (something of an annoyance if you're using X11 applications). As a whole, the freenix imports seem to be so used to doing things Their Way that the mere notion of a UNIX not having $feature makes them positively apoplectic.
Undocumented because they are not "public" apis, and not guaranteed to be supported in the next release of OSX. As long as that part is clear, go ahead.
But please, let's not complain about apple not documenting function calls.. apple is very clear about which APIs are official and supported.
Why can't I put the shortcuts for Expose onto the three keys that I NEVER use for ANYTHING? :-(
What I want to know is why Apple hasn't put a general purpose input or hotkey manager in Preferences that would let you map any key combo to any hotkey-using application.
Plus, every second keyboard these days has half a dozen extra "Multimedia" or "Internet" buttons. Why can't I map those to actions?
Why would anyone pay for a newsreader when Google Groups exists?
Um, because Google could arbitrarily change Google Groups at any moment and remove features that you depend on?
Oh, wait, Doctor Evil, that already happened.
(yes, it's their code, their hardware, they have a right to do it, the point is they can and do, and that's one good reason to do Usenet yourself instead of depending on the kindness of strangers)
So what you're doing it coming from a Windows perspective and trying to make intelligent and topical assertions about the mac development platform.
This is a mistake. Disabuse yourself of such notions. They will get you nowhere. Apple has a very different policy towards its developers. They give as much power as they can do their developers, and the tools are so good that often applications do not need to go outside the standard APIs.
You might not believe me, because of the perspective you bring to the table. Let me try and illustrate why Apple approaches this differently:
Microsoft views third party developers as competition. Microsoft is a software company, so you compete directly with them when you write a Windows app that fufils a function they want to control. Therefore, they create hidden "advantages" in the OS that only select MS developers can access correctly.
Apple, on the other hand, is a hardware company. While OS X is a serious product for them, ultimately it's leverage to sell more computers. Therefore, they make their development tools very good, and encourage 3rd party developers. If a 3rd party developer makes a killer app, they get a direct benefit from it. This is in sharp contrast to Microsoft, who would actually lose business.
Apple's "hidden" APIs are only hidden because one one of two reasons:
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