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/.

 
AAPL
$519.01
Apple Inc.
+1.05
MSFT
$40.40
Microsoft Corpora
+0.65
GOOG
$556.54
Google Inc.
+20.10

MacTech Search:
Community Search:

Software Updates via MacUpdate

PDFpenPro 6.2 - Advanced PDF toolkit for...
PDFpenPro allows users to edit PDF's easily. Add text, images and signatures. Fill out PDF forms. Merge or split PDF documents. Reorder and delete pages. Even correct text and edit graphics! Create... Read more
PDFpen 6.2 - Edit and annotate PDFs with...
PDFpen allows users to easily edit PDF's. Add text, images and signatures. Fill out PDF forms. Merge or split PDF documents. Reorder and delete pages. Even correct text and edit graphics! Features... Read more
Monolingual 1.5.9 - Remove unwanted OS X...
Monolingual is a program for removing unnecesary language resources from OS X, in order to reclaim several hundred megabytes of disk space. It requires a 64-bit capable Intel-based Mac and at least... Read more
Maya 2015 - Professional 3D modeling and...
Maya is an award-winning software and powerful, integrated 3D modeling, animation, visual effects, and rendering solution. Because Maya is based on an open architecture, all your work can be scripted... Read more
Starcraft II: Wings of Liberty 1.1.1.180...
Download the patch by launching the Starcraft II game and downloading it through the Battle.net connection within the app. Starcraft II: Wings of Liberty is a strategy game played in real-time. You... Read more
Sibelius 7.5.0 - Music notation solution...
Sibelius is the world's best-selling music notation software for Mac. It is as intuitive to use as a pen, yet so powerful that it does most things in less than the blink of an eye. The demo includes... Read more
Typinator 5.9 - Speedy and reliable text...
Typinator turbo-charges your typing productivity. Type a little. Typinator does the rest. We've all faced projects that require repetitive typing tasks. With Typinator, you can store commonly used... Read more
MYStuff Pro 2.0.16 - Create inventories...
MYStuff Pro is the most flexible way to create detail-rich inventories for your home or small business. Add items to MYStuff by dragging and dropping existing information, uploading new images, or... Read more
TurboTax 2013.r17.002 - Manage your 2013...
TurboTax guides you through your tax return step by step, does all the calculations, and checks your return for errors and overlooked deductions. It lets you file your return electronically to get... Read more
TrailRunner 3.8.769 - Route planning for...
Note: While the software is classified as freeware, it is actually donationware. Please consider making a donation to help support development. TrailRunner is the perfect companion for runners,... Read more

Latest Forum Discussions

See All

Hearthstone: Heroes of Warcraft is Avail...
Hearthstone: Heroes of Warcraft is Available on the U.S. App Store Right Now – Gogogogo! Posted by Rob Rich on April 16th, 2014 [ permalink ] | Read more »
Groundskeeper2 Review
Groundskeeper2 Review By Nadia Oxford on April 16th, 2014 Our Rating: :: SLICE THOSE ALIEN SLIMEUniversal App - Designed for iPhone and iPad Putting aside some minor control issues, Groundskeeper2 is a fun and furious action/... | Read more »
Pinnacle Studio for iPhone (Photography...
Pinnacle Studio for iPhone 5.0 Device: iOS iPhone Category: Photography Price: $9.99, Version: 5.0 (iTunes) Description: | Read more »
Season 3 of Zombies, Run! Starts Right N...
Season 3 of Zombies, Run! | Read more »
Snupps Review
Snupps Review By Jennifer Allen on April 16th, 2014 Our Rating: :: USEFUL LISTINGUniversal App - Designed for iPhone and iPad Got a huge collection that you need to organize, or just want to share with others? Snupps has it covered... | Read more »
Toad Rider Goes Free for a Limited Time,...
Toad Rider Goes Free for a Limited Time, Starting This Week Posted by Tre Lawrence on April 16th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Knights of Pen & Paper is Free for a...
Knights of Pen & Paper is Free for a Limited Time – Don’t Wait for a Natural 20, Get it Now! Posted by Rob Rich on April 16th, 2014 [ permalink ] | Read more »
R.B.I. Baseball 14 Review
R.B.I. Baseball 14 Review By Blake Grundman on April 16th, 2014 Our Rating: :: RETRO REVIVEDUniversal App - Designed for iPhone and iPad What was old is new again, as the MLB attempts to taking baseball gaming back to its retro... | Read more »
Noodlecake Studios Places Mikey Hooks on...
Noodlecake Studios Places Mikey Hooks on Sale, Releases Sneak Peek Trailer for Upcoming Sequel Mikey Boots Posted by Tre Lawrence on April 16th, 2014 [ | Read more »
Cosmic Mechanic Review
Cosmic Mechanic Review By Blake Grundman on April 16th, 2014 Our Rating: :: SLIGHTLY CREDIBLE MACHINEUniversal App - Designed for iPhone and iPad Creatives folks love the opportunity to have their wits tested, but there isn’t... | Read more »

Price Scanner via MacPrices.net

Microsoft Blinks – Drops Microsoft Office 365...
Microsoft has dropped the annual subscription fee for Microsoft Office 365 Personal – which is needed in order to create and edit documents in Microsoft Office for iPad. However, Apple’s iOS and OS X... Read more
New AVG Vault Apps for iOS and Android Help K...
AVG Technologies N.V. an online security company for 177 million active users, has announced the launch of its latest mobile application, AVG Vault. The free app introduces an innovative user... Read more
Free Local Carrot iPhone App Helps Find Fresh...
I love fresh vegetables. I’m not a vegan, although I was for several years in the 1980s, but fresh vegetables and other whole foods are still my dietary mainstays as a matter of taste rather than... Read more
Apple refurbished iPad Airs available startin...
Apple is now offering Certified Refurbished iPad Airs for up to $140 off MSRP. Apple’s one-year warranty is included with each model, and shipping is free. The following Airs are available today: -... Read more
21-inch 2.7GHz iMac on sale for $1179, save $...
B&H Photo has the 21″ 2.7GHz iMac on sale for $1179 including free shipping plus NY sales tax only. Their price is $120 off MSRP. Add an iMac to your shopping cart, and B&H will offer an... Read more
Download our app, iTracx, for iOS and Android
MacPrices is proud to offer readers a free iOS app (iPhones, iPads, & iPod touch) and Android app (Google Play and Amazon App Store) called iTracx, which allows you to glance at today’s lowest... Read more
Education discounts shave up to $300 off the...
Purchase a new Mac at The Apple Store for Education and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free, and all... Read more
Save $50 on Mac mini Server
B&H Photo has the 2012 Mac mini Server on sale for $949 including free shipping plus NY sales tax only. Their price is $50 off MSRP. Read more
PhatWare’s “Ultimate Writing App For iOS” Ren...
PhatWare Corp. has announced it has renamed its new WritePro word processing app for iPhone and iPad: WritePad Pro. The decision to change the app’s name to leverages the strong brand awareness and... Read more
Full Resolution Photo Editor Tint Mint 1.0 Re...
California based independent developer, Jeffrey Sun, creator of the iOS app Modern Editor, has released Tint Mint, a new photography app for editing enthusiasts. The app costs a dollar, and it packs... Read more

Jobs Board

*Apple* Retail - Manager - Apple (United Sta...
Job SummaryKeeping an Apple Store thriving requires a diverse set of leadership skills, and as a Manager, you're a master of them all. In the store's fast-paced, dynamic Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Retail - Market Leader - Cincinnati...
…challenges of developing individuals, building teams, and affecting growth across Apple Stores. You demonstrate successful leadership ability - focusing on excellence Read more
*Apple* Retail - Manager - SoHo - Apple (Uni...
Job SummaryKeeping an Apple Store thriving requires a diverse set of leadership skills, and as a Manager, you're a master of them all. In the store's fast-paced, dynamic Read more
Position Opening at *Apple* - Apple (United...
**Job Summary** Every day, business customers come to the Apple Store to discover what powerful, easy-to-use Apple products can do for them. As a Business Leader, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.