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

Splash Cars guide - How to paint the tow...
Splash Cars is an arcade driving game that feels like a hybrid between Dawn of the Plow and Splatoon. In it, you'll need to drive a car around to repaint areas of a town that have lost all of their color. Check out these tips to help you perform... | Read more »
The best video player on mobile
We all know the stock video player on iOS is not particularly convenient, primarily because it asks us to hook a device up to iTunes to sync video in a world that has things like Netflix. [Read more] | Read more »
Four apps to help improve your Super Bow...
Super Bowl Sunday is upon us, and whether you’re a Panthers or a Broncos fan you’re no doubt gearing up for it. [Read more] | Read more »
LooperSonic (Music)
LooperSonic 1.0 Device: iOS Universal Category: Music Price: $4.99, Version: 1.0 (iTunes) Description: LooperSonic is a multi-track audio looper and recorder that will take your loops to the next level. Use it like a loop pedal to... | Read more »
Space Grunts guide - How to survive
Space Grunts is a fast-paced roguelike from popular iOS developer, Orange Pixel. While it taps into many of the typical roguelike sensibilities, you might still find yourself caught out by a few things. We delved further to find you some helpful... | Read more »
Dreii guide - How to play well with othe...
Dreii is a rather stylish and wonderful puzzle game that’s reminiscent of cooperative games like Journey. If that sounds immensely appealing, then you should immediately get cracking and give it a whirl. We can offer you some tips and tricks on... | Read more »
Kill the Plumber World guide - How to ou...
You already know how to hop around like Mario, but do you know how to defeat him? Those are your marching orders in Kill the Plumber, and it's not always as easy as it looks. Here are some tips to get you started. This is not a seasoned platform... | Read more »
Planar Conquest (Games)
Planar Conquest 1.0 Device: iOS Universal Category: Games Price: $12.99, Version: 1.0 (iTunes) Description: IMPORTANT: Planar Conquest is compatible only with iPad 3 & newer devices, iPhone 5 & newer. It’s NOT compatible with... | Read more »
We talk to Cheetah Mobile about its plan...
Piano Tiles 2 is a fast-paced rhythm action high score chaser out now on iOS and Android. You have to tap a series of black tiles that appear on the screen in time to the music, being careful not to accidentally hit anywhere else. Do that and it's... | Read more »
Ultimate Briefcase guide - How to dodge...
Ultimate Briefcase is a simple but tricky game that’s highly dependent on how fast you can react. We can still offer you a few tips and tricks on how to survive though. Guess what? That’s exactly what we’re going to do now. Take it easy [Read more... | Read more »

Price Scanner via MacPrices.net

12-inch 1.2GHz Silver Retina MacBook on sale...
B&H Photo has the 12″ 1.2GHz Silver Retina MacBook on sale for $1399 including free shipping plus NY sales tax only. Their price is $200 off MSRP, and it’s the lowest price for this model from... Read more
iPads on sale at Target: $100 off iPad Air 2,...
Target has WiFi iPad Air 2s and iPad mini 4s on sale for up to $100 off MSRP on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale prices for... Read more
Target offers Apple Watch for $100 off MSRP
Target has Apple Watches on sale for $100 for a limited time. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store prices may vary: - Apple... Read more
Apple refurbished 2014 13-inch Retina MacBook...
Apple has Certified Refurbished 2014 13″ Retina MacBook Pros available for up to $400 off original MSRP, starting at $979. An Apple one-year warranty is included with each model, and shipping is free... Read more
Macs available for up to $300 off MSRP, $20 o...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free, and... Read more
Watch Super Bowl 50 Live On Your iPad For Fre...
Watch Super Bowl 50 LIVE on the CBS Sports app for iPad and Apple TV. Get the app and then tune in Sunday, February 7, 2016 at 6:30 PM ET to catch every moment of the big game. The CBS Sports app is... Read more
Two-thirds Of All Smart Watches Shipped In 20...
Apple dominated the smart watch market in 2015, accounting for over 12 million units and two-thirds of all shipments according to Canalys market research analysts’ estimates. Samsung returned to... Read more
12-inch 1.2GHz Retina MacBooks on sale for up...
B&H Photo has 12″ 1.2GHz Retina MacBooks on sale for $180 off MSRP. Shipping is free, and B&H charges NY tax only: - 12″ 1.2GHz Gray Retina MacBook: $1499 $100 off MSRP - 12″ 1.2GHz Silver... Read more
12-inch 1.1GHz Gray Retina MacBook on sale fo...
B&H Photo has the 12″ 1.1GHz Gray Retina MacBook on sale for $1199 including free shipping plus NY sales tax only. Their price is $100 off MSRP, and it’s the lowest price available for this model... Read more
Apple now offering full line of Certified Ref...
Apple now has a full line of Certified Refurbished 2015 21″ & 27″ iMacs available for up to $350 off MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Subject Matter Expert - Experis (Uni...
This position is for an Apple Subject Matter Expert to assist in developing the architecture, support and services for integration of Apple devices into the domain. Read more
*Apple* Macintosh OSX - Net2Source Inc. (Uni...
…: * Work Authorization : * Contact Number(Best time to reach you) : Skills : Apple Macintosh OSX Location : New York, New York. Duartion : 6+ Months The associate would Read more
Computer Operations Technician ll - *Apple*...
# Web Announcement** Apple Technical Liaison**The George Mason University, Information Technology Services (ITS), Technology Support Services, Desktop Support Read more
Restaurant Manager - Apple Gilroy Inc./Apple...
…in every aspect of daily operation. WHY YOU'LL LIKE IT: You'll be the Big Apple . You'll solve problems. You'll get to show your ability to handle the stress and Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.