TweetFollow Us on Twitter

Jun 98 Online

Volume Number: 14 (1998)
Issue Number: 6
Column Tag: MacTech Online

Plug In and Reach Out

by Jeff Clites, online@mactech.com

A plug-in architecture can be a clever way to add power and value to your application. It allows third parties to extend the capabilities of your product, and allows you to do the same without the need to redistribute the entire application to end users, and without the danger of adding bugs to the core code as you add features.

The Component Manager

It is natural to think of an application plug-in as analogous to a system extension, but there is a crucial difference: extensible applications are specifically designed to work with plug-ins, and have a well-defined interface through which the plug-ins operate, while INITs usually do their work despite the lack of such an interface, relying on low-level mechanisms such as trap patching. As a result, plug-ins don't bring the instability often associated with system extensions, and they tend to provide an application with a specific service or capability, rather than modifying global behavior.

Despite this distinction, certain parts of the Mac OS are designed to accommodate plug-ins, and they do so using a powerful tool that you can use to give your own applications a plug-in architecture: the Component Manager. Apple likens the Component Manager to a Resource Manager which acts on function objects rather than data objects. If you have ever executed a compiled script from within an application, you have used the Component Manager. Many parts of the Mac OS are implemented via components - AppleScript and Frontier are Scripting Components, QuickTime uses components for image decompression and for video effects, and the Translation Manager uses components to enable Mac OS Easy Open to covert files between formats.

You can write components which will only be used by your application, or which will provide their services globally, to any application which requests them. Start learning about the Component Manager from its chapter in Inside Macintosh: More Macintosh Toolbox, and then visit the QuickTime 3.0 documentation for recent changes. Also be sure to look at the sample code which Apple has provided. There is older code, which shows you how to write a simple component, and newer code on the QuickTime 3.0 web site which demonstrates how you can write components which apply video effects or allow applications to import images stored in a new format. To round things out, there is a Technote describing how the Component Manager handles PowerPC native components.

Inside Macintosh: More Macintosh Toolbox
http://devworld.apple.com/dev/techsupport/insidemac/MoreToolbox/MoreToolbox-2.html
Inside Macintosh: QuickTime Components
http://devworld.apple.com/dev/techsupport/insidemac/QTComponents/QTComponents-2.html
QuickTime 3.0 Developer Index
http://www.apple.com/quicktime/preview/develop/index.htm
Component Manager Sample Code
ftp://dev.apple.com/devworld/./Sample_Code/QuickTime/Component_Manager.sit.hqx
QuickTime 3.0 Sample Code
http://www.apple.com/quicktime/preview/develop/samplecode.html
Technote 1004: On QuickTime Component Manager 3.0 & PowerPC Native Components
http://devworld.apple.com/dev/technotes/tn/tn1004.html

The most expansive example of using a component to supply services to multiple applications is Internet Config, the source to which is in the public domain. Internet Config has become indispensable as more and more applications become internet-savvy, and it's a great example of using a component to save programmers from the need to code in the same functionality over and over. The author's ftp site has the source, which you can use as an example of good component design, and a programmer's kit which shows you how to use Internet Config from within your application. Dan Crevier has also written IC++, a C++ wrapper class for Internet Config, which illustrates how you can make it even easier for you (or others) to call your component from inside an application.

Internet Config FTP Site
ftp://ftp.quinn.echidna.id.au/Others/Quinn/Config/
IC++ Wrapper Class for Internet Config
http://www.boingo.com/dan/software/Programming.html
Using the Internet Configuration System
www.mactech.com/articles/mactech/Vol.11/11.04/Internet-Config/index.html
Implementing Shared Internet Preferences With Internet Config
www.mactech.com/articles/develop/issue_23/quinn.html

Photoshop Plug-Ins

Probably the most well-known type of application plug-ins are Photoshop plug-ins; in fact, and entire industry has been built around them. You can get in on the fun by downloading the Photoshop SDK from Adobe, which also has SDKs for plug-ins to their other applications, including Illustrator and Acrobat. There are actually several different types of Photoshop plug-ins - the most common are filters, which directly manipulate images, but there are also image acquisition plug-ins, which let you drives devices such as scanners from within the application, and import and export plug-ins.

It's possible to support Photoshop plug-ins in your own application, and many third parties do this to increase, for instance, the image-manipulation power of their applications. NIH Image is one example. It is an image processing and analysis application developed by the National Institutes of Health and is widely used for scientific imaging. Not only is it free, but its source code is in the public domain. It supports some Photoshop plug-ins, so it can serve as a test bed for those developers who want to experiment but don't own Photoshop, or who are designing their plug-ins for the widest range of compatibility. The source code, of course, can help those looking to support Photoshop plug-ins in their own application, or who want a model for a plug-in architecture in general. The NIH Image ftp site also has a directory full of plug-ins, some with source code, to serve as examples to developers and to augment Adobe's SDK.

Adobe Developers Relations SDKs
http://www.adobe.com/supportservice/devrelations/sdks.html
NIH Image Home Page
http://rsb.info.nih.gov/nih-image/
NIH Image Mailing List
http://www.soils.agri.umn.edu/infoserv/lists/nih-image/

Last, But Not Least

A plug-in architecture is a Good Thing. It can reduce the size of your application, decrease its memory footprint, and promote good design by encouraging you to factor your application into functionally independent pieces and prepare it for future enhancements. While implementing a new design strategy, it's always good to have some printed material on hand. Plug-ins are code fragments at heart, and the definitive text on these is A Fragment of Your Imagination, by Joe Zobkiw. It has chapters on the Component Manager and on Photoshop filters, as well as covering system extensions and most other related topics, and there is even an accompanying web site.

A Fragment of Your Imagination
http://www.triplesoft.com/fragment/

These and other links are available from the MacTech Online web pages at www.mactech.com/online/.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

iDefrag 5.0.0 - Disk defragmentation and...
iDefrag helps defragment and optimize your disk for improved performance. Features include: Supports HFS and HFS+ (Mac OS Extended). Supports case sensitive and journaled filesystems. Supports... Read more
PCalc 4.2 - Full-featured scientific cal...
PCalc is a full-featured, scriptable scientific calculator with support for hexadecimal, octal, and binary calculations, as well as an RPN mode, programmable functions, and an extensive set of unit... Read more
FileZilla 3.10.2 - Fast and reliable FTP...
FileZilla (ported from Windows) is a fast and reliable FTP client and server with lots of useful features and an intuitive interface. Version 3.10.2: Note: Now requires a 64-bit Intel processor.... Read more
The Hit List 1.1.11 - Advanced reminder...
The Hit List manages the daily chaos of your modern life. It's easy to learn - it's as easy as making lists. And it's powerful enough to let you plan, then forget, then act when the time is right.... Read more
Bartender 1.2.32 - Organize your menu ba...
Bartender lets you organize your menu bar apps. Features: Lets you tidy your menu bar apps how you want. See your menu bar apps when you want. Hide the apps you need to run, but do not need to... Read more
ClamXav 2.7.5 - Free virus checker, base...
ClamXav is a free virus checker for OS X. It uses the tried, tested, and very popular ClamAV open source antivirus engine as a back end. I hope you like and use ClamXav a lot and that it helps keep... Read more
xScope 4.1.2 - Onscreen graphic measurem...
xScope is powerful set of tools that are ideal for measuring, inspecting, and testing on-screen graphics and layouts. Its tools float above your desktop windows and can be accessed via a toolbar,... Read more
MacFamilyTree 7.3.3 - 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
Skype 7.5.0.738 - Voice-over-internet ph...
Skype allows you to talk to friends, family and co-workers across the Internet without the inconvenience of long distance telephone charges. Using peer-to-peer data transmission technology, Skype... Read more
PushPal 3.0 - Mirror Android notificatio...
PushPal is a client for Pushbullet, which automatically shows you all of your phone's notifications right on your computer. This means you can see who's calling or read text messages even if your... Read more

It Came From Canada: Jurojin: Immortal N...
At this point it’s pretty safe to say that no MOBA is going to dethrone Dota 2 and League of Legends anytime soon. After all, if Batman can’t do it, nobody can. However, with a genre as popular and profitable as this one, there’s still room for... | Read more »
Tiny Farm – Animals, Tractors and Advent...
Tiny Farm – Animals, Tractors and Adventures! Review By Amy Solomon on March 3rd, 2015 Our Rating: :: LIVELY LANDSCAPESUniversal App - Designed for iPhone and iPad Tiny Farm – Animals, Tractors and Adventures! includes farm-related... | Read more »
This Week at 148Apps: February 23-27, 20...
Final February Fun at 148Apps   How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you’re looking for. The ones we love become Editor’s Choice, standing out... | Read more »
GDC 2015 – Does Not Commute is Definitel...
GDC 2015 – Does Not Commute is Definitely a Game You Should Keep an Eye on Posted by Rob Rich on March 2nd, 2015 [ permalink ] We were teased about Mediocre Games’ (Smash Hit, | Read more »
F84 Games & POW! Announce Stan Lee V...
F84 Games has announced that it is working with legendary comic creator Stan Lee and POW! Entertainment to produce Stan Lee’s Hero Command. The game will be a action adventure of heroic proportions. | Read more »
Setlyst Keeps Your Set Straight So You C...
Setlyst Keeps Your Set Straight So You Can Focus On Rocking Out. Posted by Jessica Fisher on March 2nd, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Space is Vast, So Space Agency Has a Vas...
Space is Vast, So Space Agency Has a Vast New Update! Posted by Jessica Fisher on March 2nd, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Size DOES Matter Review
Size DOES Matter Review By Campbell Bird on March 2nd, 2015 Our Rating: :: HARD TO BEATUniversal App - Designed for iPhone and iPad This rhythm game has a unique control scheme and performance system that make it feel like a true... | Read more »
The first ever action 3D card battler Al...
On the other hand, you probably haven’t played an action 3D card battler – until now. Step forward, All Star Legion. All Star Legion is a 3D QTE-based action RPG card battler, but fear not – the game itself isn’t as convoluted as its description.... | Read more »
Travel Back to the 1980s With the Making...
Headup Games has released a hilarious making of video for its upcoming title, Pixel Heroes: Byte & Magic. The game is a RPG/Roguelike where you control three heroes set to save the township of Pixton from an evil cult called The Sons of Dawn.... | Read more »

Price Scanner via MacPrices.net

Sale! 15-inch 2.2GHz Retina MacBook Pro for $...
 Best Buy has the 15″ 2.2GHz Retina MacBook Pro on sale for $1774.99 $1799.99, or $225 off MSRP. Choose free home shipping or free local store pickup (if available). Price valid for online orders... Read more
27-inch 3.5GHz 5K iMac in stock today and on...
 B&H Photo has the 27″ 3.5GHz 5K iMac in stock today and on sale for $2299 including free shipping plus NY sales tax only. Their price is $200 off MSRP, and it’s the lowest price available for... Read more
Apple Launches Free Web-Based Pages and Other...
Apple’s new Web-only access to iWork productivity apps is a free level of iCloud service available to anyone, including people who don’t own or use Apple devices. The service includes access to Apple... Read more
Survey Reveals Solid State Disk (SSD) Technol...
In a recent SSD technology use survey, Kroll Ontrack, a firm specializing in data recovery, found that while nearly 90 percent of respondents leverage the performance and reliability benefits of SSD... Read more
Save up to $600 with Apple refurbished Mac Pr...
The Apple Store is offering Apple Certified Refurbished Mac Pros for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The... 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
Apple CEO Tim Cook to Deliver 2015 George Was...
Apple CEO Tim Cook will deliver the George Washington University’s Commencement address to GWU grads on May 17, at which time he will also be awarded an honorary doctorate of public service from the... Read more
Apple restocks refurbished Mac minis for up t...
The Apple Store has restocked Apple Certified Refurbished 2014 Mac minis, with models available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: - 1.4GHz... Read more
Save up to $50 on iPad Air 2s, NY tax only, f...
 B&H Photo has iPad Air 2s on sale for $50 off MSRP including free shipping plus NY sales tax only: - 16GB iPad Air 2 WiFi: $469.99 $30 off - 64GB iPad Air 2 WiFi: $549 $50 off - 128GB iPad Air 2... Read more
16GB iPad Air 2 on sale for $447, save $52
Walmart has the 16GB iPad Air 2 WiFi on sale for $446.99 on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale price for online orders only,... Read more

Jobs Board

*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
*Apple* Pay Automation Engineer - iOS System...
**Job Summary** At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring passion and dedication to your job 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
Event Director, *Apple* Retail Marketing -...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global engagement strategy and team. Delivering an overarching brand 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.