TweetFollow Us on Twitter

Feb 00 Factory Floor

Volume Number: 16 (2000)
Issue Number: 2
Column Tag: From the Factory Floor

Carbon and PowerPlant

By Gregory Dow ©2000 Gregory Dow. All rights reserved.

Web apps with Lasso and FileMaker Pro

Gregory Dow is the senior architect and original author of PowerPlant, which he started writing for Metrowerks in 1993. Greg works from his home in Berkeley, Calif., where he has been leading a discussion group of Mac programmers for 12 years. The group meets every other week in a local restaurant, sharing industry gossip and technical tips. Greg enjoys helping fellow programmers and he is a regular contributor to the comp.sys.mac.oop.powerplant newsgroup.

Biography

Gregory Dow is the original author of PowerPlant, which he started writing in 1993. Greg works from his home in Berkeley, California, where he has been leading a discussion group of Mac programmers for 12 years. The group meets every other week in a local restaurant, sharing industry gossip and technical tips. Greg enjoys helping fellow programmers and he is a regular contributor to the comp.sys.mac.oop.powerplant newsgroup.

What is your overall opinion of Carbon?

Greg: I think that Carbon is not only a wonderful technology, but also a great name. Carbon. It's the sixth element in the Periodic Table. It's the basis of all organic life. As graphite, Carbon is the softest substance. As diamond,

Carbon is the hardest substance. In terms of puns and metaphors, Carbon puts the Mac Toolbox at the same level as Java.

On the technical side, I think there are two important facets of Carbon. First, Carbon will run on the upcoming Mac OS X as well as on all systems back to Mac OS 8.1. Programmers don't have to choose between developing for the cutting edge systems and being compatible with a large installed base of machines - they can do both.

Second, Carbon extends the life of existing source code because it includes a large subset of the classic Mac OS 8 Toolbox. Over the years, Apple has been very good about maintaining backward compatibility. When new OS versions come out, existing programs usually continue to work, or require only minor modifications. You don't need to rewrite from scratch. Carbon continues this important tradition, although the required changes are more substantial.

What factors should someone consider before adopting Carbon?

Greg: Moving to a new technology always entails some risks. Remembering ill-fated technologies as QuickDraw GX, OpenDoc, and Copland, some developers are naturally skeptical about Apple's commitment to Carbon.

However, Apple has a good track record with Carbon. The Carbon message was consistent at the Worldwide Developers Conferences in 1998 and 1999. Carbon 1.0 shipped with Mac OS 9, and Carbon is included in the Developer Preview 2 version of Mac OS X. Also, by the time you read this article, Carbon 1.0.2, which runs on Mac OS 8.1 or later, will be out.

One potential problem is that Carbon does not ship with Mac OS 8. Developers can license Carbon from Apple for distribution with their products, but this is an extra hassle that might deter hobbyists. Furthermore, the Carbon library is about 1 MB in size, considerably large to bundle with a small program.

Another problem is that Carbon does not run on systems prior to Mac OS 8.1 and supports only PowerPC machines. There is no workaround for this. If you need to support 68K machines, System 7, or even earlier systems, you cannot use Carbon. You would need to decide if it is worth the development effort to produce both Carbon and Classic versions.

Developers with existing programs also need to make that same decision. They should ask themselves, "do the benefits of Carbon outweigh the costs of porting the source code?" Carbon is not a runtime feature. It is not like the Appearance Manager where you are able to weak link a library, then decide at runtime whether to use one set of routines or another. You cannot gradually Carbonize. It's all or nothing.

In Mac OS 8 and 9, there are not any significant advantages to using Carbon, and Classic programs will still run on Mac OS X. The advantages come from Carbon on Mac OS X, where the three major benefits are protected memory, dynamic heap sizes, and pre-emptive multitasking. The value of these benefits depends greatly on what a program does, although all programs are better off with protected memory because it helps insulate a program from bugs in other programs.

Dynamic heap sizes will help programs that use a variable amount of memory. This includes programs that open multiple documents or otherwise deal with indeterminate amounts of data. Pre-emptive multitasking can make the entire system feel more responsive and is very good for programs that perform lengthy computations or otherwise need regular processing time.

What kinds of changes will people need to make to support Carbon?

Greg: I classify the differences between the Carbon and Classic Toolboxes into three categories: syntactic, interface modification, and feature replacement.

Syntactic changes usually require only one or two line changes to source code. The simplest are name changes, where Apple has renamed a symbol in order to be more consistent with naming conventions. Such changes are not new to Carbon, as they occur with almost every new version of Apple's Universal Interfaces.

Other syntactic changes result from many Carbon Toolbox data structures being opaque, meaning that their format is private and not directly accessible. You need to use an accessor function. For example, in Classic, you can access the font for the current port as follows:

	GrafPtr	currentPort;
	GetPort(&currentPort);
	short		currentFont = currentPort->txFont;

Referring to currentPort->txFont depends on the exact size and layout of the GrafPort struct. Any change to that struct and the above code breaks. In Carbon, you must call a function to get a port's font:

	short		currentFont = GetPortTextFont(currentPort);

The GrafPort struct is opaque, and not even defined in the header files for Carbon. As long as the function GetPortTextFont() continues to return the font for a port, Apple can change how GrafPorts are implemented without breaking existing programs. This makes it much easier for Apple to enhance the system software.

Interface modification describes cases where Carbon and Classic have different ways for accomplishing the same task. A very simple example is initializing the Toolbox managers. With Classic, you need to call functions such as InitGraf(), InitWindows(), and InitMenus(). With Carbon, you do not call any of these functions. Carbon initializes the Toolbox automatically.

Another example of different interfaces is the Scrap Manager for dealing with clipboard data. For Classic, you use the functions GetScrap(), PutScrap(), and ZeroScrap(). For Carbon, you use the functions GetScrapFlavorData(), PutScrapFlavor(), and ClearCurrentScrap(). There are small differences in how you use the functions, but it's mostly a one-to-one correspondence.

The Printing Manager also has a different interface in Carbon. There are new data structures and functions. However, there are routines for converting between the Classic and Carbon data structures. This is very convenient, as a lot of Classic printing code relies on directly accessing and storing the information in a PrintRecord.

The changes that will probably be the most difficult are feature replacements. Carbon removes support for some system features such as Standard File, MacTCP, and balloon help. Developers must convert code to use alternate features that are supported. For the aforementioned features, suitable replacements are Navigation Services, Open Transport, and MacHelp. If your programs rely heavily on an unsupported feature, you will have a lot of work to do.

How have you implemented Carbon support in PowerPlant?

Greg: PowerPlant 2.0, the version in CodeWarrior Professional Edition, Version 5.0, is being enhanced so that it can be used to build both Carbon and Classic programs. Carbon is another possible target for a project, along with PowerPC and 68K.

Since Classic and Carbon have different interfaces, there is a lot of conditional compilation. Universal Interfaces 3.3 and later include Carbon support, controlled by the preprocessor symbol TARGET_API_MAC_CARBON. PowerPlant defines its own PP_Target_Carbon and PP_Target_Classic symbols.

For the most part, I have tried to avoid having code within functions that looks like:

	#if PP_Target_Carbon
		// Carbon code here
	#else
		// Classic code here
	#endif

Such code is hard to read and maintain.

In cases where Carbon has new accessor functions, I use inline functions with the same name that are defined only for Classic. For example, using the accessor for the font of a port previously mentioned, I have defined:

	inline short GetPortTextFont ( GrafPtr port )
	{
		return port->txFont;
	}

This definition, along with all the other accessor functions that PowerPlant uses, is within a single header file and bracketed by an #if so that it is not only defined for Classic targets. The PowerPlant sources always call the accessor function. For Carbon, this is an actual function call. For Classic, the inline function becomes a direct access of the data value.

In cases where Carbon and Classic have different interfaces, I define a common interface with separate implementations. For example, I have defined a UScrap namespace with the functions GetData(), SetData() and ClearData(). There are two implementations of each of these functions, one for Carbon and one for Classic. Client code then makes calls such as UScrap::GetData(), with the setting of the conditional compilation flags determining which function is used.

PowerPlant already has support for both Standard File and Navigation Services using the same interface. There are three options: always use Standard File, always use Navigation Services, and use Navigation Services if it is available at runtime (otherwise use Standard File). For Classic, you can use any of these options. For Carbon, you must always use Navigation Services.

Likewise, the PowerPlant networking classes have always provided an abstraction layer that supports both Open Transport and MacTCP. Under Carbon, you must use Open Transport.

How much work is required to Carbonize PowerPlant programs?

Greg: That really depends on what the programs do. People will need to do the same kinds of things that I did with the PowerPlant sources. For simple programs, that will mostly be the syntactic changes of using accessor functions.

Printing is the biggest change. PowerPlant will handle printing the built-in panes and views. But people will need to update custom views with non-trivial printing features (anything that accesses the PrintRecord).

Otherwise, updating an existing project requires minimal changes. You need to create a new target, remove some old files and add some new ones, and set up a prefix file with the correct options.
 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Parallels Desktop 10.2.0 - Run Windows a...
Parallels Desktop is simply the world's bestselling, top-rated, and most trusted solution for running Windows applications on your Mac. With Parallels Desktop for Mac, you can seamlessly run both... Read more
LaunchBar 6.2 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
Firefox 37.0 - Fast, safe Web browser. (...
Firefox offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals and casual... Read more
Arq 4.11 - Online backup to Google Drive...
Arq is super-easy online backup for the Mac. Back up to your own Google Drive storage (15GB free storage), your own Amazon Glacier ($.01/GB per month storage) or S3, or any SFTP server. Arq backs up... Read more
MacFamilyTree 7.3.4 - Create and explore...
MacFamilyTree gives genealogy a facelift: it's modern, interactive, incredibly fast, and easy to use. We're convinced that generations of chroniclers would have loved to trade in their genealogy... Read more
Yummy FTP 1.10.2 - FTP/SFTP/FTPS client...
Yummy FTP is an FTP + SFTP + FTPS file transfer client which focuses on speed, reliability and productivity. Whether you need to transfer a few files or a few thousand, schedule automatic backups, or... Read more
VueScan 9.5.08 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Iridient Developer 3.0.1 - Powerful imag...
Iridient Developer (was RAW Developer) is a powerful image conversion application designed specifically for OS X. Iridient Developer gives advanced photographers total control over every aspect of... Read more
Monodraw 0.8.4.1 - Powerful ASCII art ed...
Monodraw allows you to easily create text-based art (like diagrams, layouts, flow charts) and visually represent algorithms, data structures, binary formats and more. Because it's all just text, it... Read more
Air Video Server HD 2.1.0 - Stream video...
Air Video Server HD streams videos instantly from your computer on your iPhone, iPad, iPod touch or Apple TV. No need to worry about converting or transferring files. We took everything that was... Read more

Marvel Mighty Heroes, the Ultimate Marve...
DeNA and Marvel Entertainment have brought us a new action-packed brawler: Marvel Mighty Heroes. You can play with up to four of your friends as you favorite marvel heroes like Iron Man, Thor, Spider-Man, Captain America, Star-Lord, Hulk, and... | Read more »
Take Note - The Jot Script 2 Evernote Ed...
Adonit's Jot Script 2 sylus has an all-new edition that's meant to be Evernote's BFF. The sylus has been redesigned to work better with iPads and give you faster stroke tracking, smoother line rendering, and better tip-to-line accuracy. | Read more »
INFINIT Lets Mobile Users Send Files of...
Infinit  is a file sharing app that ignores file size limits. It maintains the original quality of your photos and videos so you can be sure they look awesome after sending. You can move entire albums of photos or full HD films from your iPhone to... | Read more »
Serious Sam Double D Developer is Making...
There's nothing like the thrill of watching a horse race, especially when the horses are drunk.  | Read more »
2K Announces WWE 2K, Mobile's First...
It seems like this month has been pretty big for wrestling. First Wrestlemania, then 2K has announces that they're releasing  WWE 2K for iOS. It's a simulation-based WWE game where you'll get to play with several WWE superstars such as John Cena, ... | Read more »
How the Apple Watch Could Change the Fac...
The Apple Watch is still a ways out, but my previous musings on the wearable’s various features got me thinking: what might it be like a year after launch? Two years? Five years? What if it becomes a symbiotic part of the iOS framework to the point... | Read more »
You Can Start Challenging Your Friends t...
Last year we reported that Sebastian Gosztyla's new game, Dual, was theorized to be released sometime during the summer of 2014. Sadly that did not become a reality, but the good news it there is now an official release date. | Read more »
Forgotten Memories : Alternate Realities...
Forgotten Memories : Alternate Realities, from Psychoz Interactive, is planned for release on April 23. The Resident Evil, Silent Hill, and Alone in the Dark inspired horror game puts you in the shoes of Rose Hawkins as she searches for a missing... | Read more »
Pie In The Sky: A Pizza Odyssey (Games)
Pie In The Sky: A Pizza Odyssey 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: A game about delivering pizza. In space. | Read more »
Chosen Gives Hopeful Singers, Songwriter...
If YouTube videos and reality TV shows like The Voice have taught us one thing, it’s that there are a lot of people out there who are anxious to show the world their talents. And if they’ve taught us a second thing, it’s that there’s an almost... | Read more »

Price Scanner via MacPrices.net

Will Microsoft’s Surface 3 Give The 12-inch M...
The more I ruminate over the new 12-inch MacBook, the more it occurs that it’s probably going to be more of a cannibalization threat to high-end iPads (including a new 12-inch ‘Pad when/if that... Read more
13-inch 2.4GHz Retina MacBook Pro available f...
MacMall has the 2013 13″ 2.4GHz/128GB Retina MacBook Pro available for $949.99 for a limited time. Shipping is free. Their price is $350 off original MSRP, and it’s the only sub-$1000 new Retina... Read more
Adobe Brings Powerful Layout-Design Capabilit...
Adobe today announced the availability of Adobe Comp CC, a free iPad app that enables rapid creation of layout concepts for mobile, Web and print projects. With Comp CC, designers can rough out and... Read more
13-inch 2.6GHz/256GB Retina MacBook Pro avail...
Best Buy has clearance 2014 13″ 2.6GHz/256GB Retina MacBook Pros available for $1199.99 including free shipping. Their price is $300 off original MSRP, and it’s the lowest price for this model.... Read more
Updated Mac Price Trackers
We’ve updated our Mac Price Trackers with the latest information on prices, bundles, and availability on systems from Apple’s authorized internet/catalog resellers: - 15″ MacBook Pros - 13″ MacBook... Read more
21-inch 1.4GHz iMac on sale for $999, save $1...
Best Buy has the 21″ 1.4GHz iMac on sale for $999.99 on their online store. Choose free shipping or free local store pick up. Price is for online orders only, in-store prices may vary. Their price is... Read more
2.6GHz Mac mini on sale for $649, save $50
Amazon has the 2.6GHz Mac mini on sale for $649.99 including free shipping. Their price is $50 off MSRP, and it’s the lowest price available for this model. Read more
Textkraft Professional 3.2 Powerful iPad Text...
Finally it’s springtime, at least theoretically in my neck of the woods, where we’re still navigating canyons between towering snowbanks with temperatures well below freezing in winter weather that... Read more
Apple offering refurbished 27-inch 5K iMacs f...
The Apple Store is offering Apple Certified Refurbished 27″ 3.5GHz 5K iMacs for $2119 including free shipping. Their price is $380 off the price of new models, and it’s the lowest price available for... Read more
16GB iPad mini on sale for $199, save $50
Walmart has 16GB iPad minis (1st generation) available for $199.99 on their online store, including free shipping. Their price is $50 off MSRP. Online orders only. Read more

Jobs Board

DevOps Software Engineer - *Apple* Pay, iOS...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Sr. Technical Services Consultant, *Apple*...
**Job Summary** Apple Professional Services (APS) has an opening for a senior technical position that contributes to Apple 's efforts for strategic and transactional Read more
Lead *Apple* Solutions Consultant - Retail...
**Job Summary** Job Summary The Lead ASC is an Apple employee who serves as the Apple business manager and influencer in a hyper-business critical Reseller's store Read more
*Apple* Pay - Site Reliability Engineer - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.