TweetFollow Us on Twitter

Winter 92 - BE OUR GUEST

BE OUR GUEST

BACKGROUND-ONLY APPLICATIONS IN SYSTEM 7

C. K. HAUN


One of the least heralded new features of System 7, but nonetheless a very important one, is full support for faceless background applications (FBAs). An FBA is a full-fledged application that's invisible to the user. It has its own event loop, and it receives time and some events like any other application, but it doesn't have a menu bar, windows, dialogs, or other graphic components. An FBA is a normal file of type 'APPL'.

FBAs are, by a stretch of the imagination, similar to UNIX® daemons. The purpose of an FBA is to provide services to other applications or to monitor the system. For instance, an application that periodically checks your hard drive for files that haven't been backed up lately is a perfect candidate for FBA status. Thus, an FBA can be a silent partner to your application, INIT, cdev, desk accessory, or driver.

An FBA is the best way to provide certain services. For example, an FBA paired with a desk accessory can enable the DA to send Apple events, something a DA cannot usually do. (See the AECDEV/AEDAEMON sample in the snippets provided with the DTS Sample Code on theDeveloper CD Series disc.) An FBA can replace an INIT that patches traps to get time and provides services, or it can replace a driver that depended on periodic run messages to operate. Converting to an FBA not only frees you from having to patch to get the time you need, but also gives you a fully supported and documented interface and design. You get all the advantages of a full application, without the overhead of a user interface.

An FBA can also be an application manager for a suite of applications. With an FBA, you can control the launching of and communication between applications, using LaunchApplication and Apple events.

Writing an FBA is simple. An FBA is a subset of a standard Macintosh application, consisting of a minimal event loop and the code to handle two types of events, null events and high-level events. No other events are sent to an FBA. This makes a great deal of sense, since every other event (keystroke, mouse click, and such) is designed for foreground applications.

The SmallDaemon backgrounder shell included on theDeveloper CD Series disc shows just how simple the basics of an FBA are:

Boolean         gQuit = false;
EventRecord     gERecord;
unsigned long   gMySleep = 50000; /* A long, long time */
main()
{
    /* Routine for installing my Apple event handlers. 
       Need to install the four required
       handlers, plus handlers for any other events
       I want to accept. */
    InitAEStuff();
    while (gQuit == false) {
        /* A normal call to WaitNextEvent. I want
           only highLevelEvents, since all other
           events relate to interface actions, and I
           have no interface. */
        if (WaitNextEvent(highLevelEventMask, &gERecord, gMySleep,
               0)) {
            /* I'll get only null and high-level events. */
            switch (gERecord.what) {
            case nullEvent:
            /* No null processing in this sample. */
            break;
            
            case kHighLevelEvent:
            /* Get a high-level event (an Apple event) and process */
            /* it. */
            DoHighLevel(&gERecord);
            break;
            }
        }
    }
}

As you can see, there's not much there. The first thing you'll notice is that an FBA doesn't start up any managers. All the managers you normally start are based on user interface actions. Thus, they should not  be called in an FBA--in fact, calling them will cause your FBA to crash. There's one exception to this rule: you can initialize QuickDraw, butonly to provide yourself with off-screen grafPorts or to use some QuickDraw functions. Do not do any actual screen drawing from an FBA.

You'll also notice that you don't pass a mouse region to WaitNextEvent. That's obvious, since you're never in the foreground and have no windows or mouse control to track. And the only events you'll be handling are null events and high-level events (Apple events).

The next step is to make sure the system knows that you're a background-only application. You do this with a SIZE resource, by setting the canBackground and onlyBackground bits to true. When the Finder launches your FBA, it checks these bits and finds that you're a background-only application.

Some tips and techniques to keep in mind:

  • Always remember that an FBA is invisible to the user. An FBA doesnot  show up in the Process menu or in the Finder About window. Also, its heap memory is added to the system size thermometer bar in the Finder About window, even though it has its own application heap. The user often will have no idea that it's running, so be friendly.
  • Being friendly means yielding time. Have a very large sleep time when you're not actually doing some processing. If you don't, users will think that their machine has slowed down inexplicably. You can always use the new Process Manager call WakeUpProcess to get yourself back into fast processing when you need to.
  • Being friendly also means making sure you're occupying thesmallest  heap size you can possibly run in. Again, users may never know that your FBA exists, so if you eat up a bunch of memory in your FBA, users will not understand why they've lost so much memory. Be conservative.
  • Putting your FBA in the Startup Items folder in the System Folder is also a good idea. That will ensure that your FBA is launched right after Finder startup and will put the FBA high in the Process Manager's heap, preventing fragmentation of application memory space.
  • Use WakeUpProcess to get your FBA running. Keep your sleep time at maximum normally, and when you need to start doing null processing (in response to an Apple event or PPC completion routine, for example) use the Process Manager to wake yourself up. WakeUpProcess can be called at interrupt time. Then, when you've finished processing, drop back to a maximum sleep time.

For further information and help with writing an FBA, refer to the Process Manager chapter ofInside Macintosh Volume VI. Then try it--you'll like it!

C. K. HAUN has been programming Apple computers since 1979, writing commercial education, utility, and game applications for the Apple II, IIGS, and Macintosh, with some occasional dark forays into the Big Blue world. (It paid the rent.) He currently works in Developer Technical Support and focuses mainly on Apple events and the Edition Manager. Besides working to provide the best possible support to developers, he's been trying to organize the Silicon Valley chapter of Heck's Moofers, a motorcycle club devoted to the precept that computer nerds on bikes can raise heck too, darn it. And yes, that really is  his mustache.*

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

NetShade 6.3.1 - Browse privately using...
NetShade is an anonymous proxy and VPN app+service for Mac. Unblock your Internet through NetShade's high-speed proxy and VPN servers spanning seven countries. NetShade masks your IP address as you... Read more
Dragon Dictate 4.0.7 - Premium voice-rec...
With Dragon Dictate speech recognition software, you can use your voice to create and edit text or interact with your favorite Mac applications. Far more than just speech-to-text, Dragon Dictate lets... Read more
Persecond 1.0.2 - Timelapse video made e...
Persecond is the easy, fun way to create a beautiful timelapse video. Import an image sequence from any camera, trim the length of your video, adjust the speed and playback direction, and you’re done... Read more
GIMP 2.8.14p2 - Powerful, free image edi...
GIMP is a multi-platform photo manipulation tool. GIMP is an acronym for GNU Image Manipulation Program. The GIMP is suitable for a variety of image manipulation tasks, including photo retouching,... Read more
Sandvox 2.10.2 - Easily build eye-catchi...
Sandvox is for Mac users who want to create a professional looking website quickly and easily. With Sandvox, you don't need to be a Web genius to build a stylish, feature-rich, standards-compliant... Read more
LibreOffice 5.0.1.2 - Free, open-source...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
f.lux 36.1 - Adjusts the color of your d...
f.lux makes the color of your computer's display adapt to the time of day, warm at night and like sunlight during the day. Ever notice how people texting at night have that eerie blue glow? Or wake... Read more
VirtualBox 5.0.2 - x86 virtualization so...
VirtualBox is a family of powerful x86 virtualization products for enterprise as well as home use. Not only is VirtualBox an extremely feature rich, high performance product for enterprise customers... Read more
File Juicer 4.43 - Extract images, video...
File Juicer is a drag-and-drop can opener and data archaeologist. Its specialty is to find and extract images, video, audio, or text from files which are hard to open in other ways. In computer... Read more
Apple MainStage 3.2 - Live performance t...
MainStage 3 makes it easy to bring to the stage all the same instruments and effects that you love in your recording. Everything from the Sound Library and Smart Controls you're familiar with from... Read more

ReBoard: Revolutionary Keyboard (Utilit...
ReBoard: Revolutionary Keyboard 1.0 Device: iOS Universal Category: Utilities Price: $1.99, Version: 1.0 (iTunes) Description: Do everything within the keyboard without switching apps! If you are in WhatsApp, how do you schedule a... | Read more »
Tiny Empire (Games)
Tiny Empire 1.1.3 Device: iOS Universal Category: Games Price: $2.99, Version: 1.1.3 (iTunes) Description: Launch cannonballs and blow tiny orcs into thousands of pieces in this intuitive fantasy-themed puzzle shooter! Embark on an... | Read more »
Astropad Mini (Productivity)
Astropad Mini 1.0 Device: iOS iPhone Category: Productivity Price: $4.99, Version: 1.0 (iTunes) Description: *** 50% off introductory price! ​*** Get the high-end experience of a Wacom tablet at a fraction of the price with Astropad... | Read more »
Emo Chorus (Music)
Emo Chorus 1.0.0 Device: iOS Universal Category: Music Price: $1.99, Version: 1.0.0 (iTunes) Description: Realistic Choir simulator ranging from simple Chorus emulation to full ensemble Choir with 128 members. ### introductory offer... | Read more »
Forest Spirit (Games)
Forest Spirit 1.0.5 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.5 (iTunes) Description: | Read more »
Ski Safari 2 (Games)
Ski Safari 2 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: The world's most fantastical, fun, family-friendly skiing game is back and better than ever! Play as Sven's sister Evana, share... | Read more »
Lara Croft GO (Games)
Lara Croft GO 1.0.47768 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.47768 (iTunes) Description: Lara Croft GO is a turn based puzzle-adventure set in a long-forgotten world. Explore the ruins of an ancient... | Read more »
Whispering Willows (Games)
Whispering Willows 1.23 Device: iOS Universal Category: Games Price: $4.99, Version: 1.23 (iTunes) Description: **LAUNCH SALE 50% OFF** - Whispering Willows is on sale for 50% off ($4.99) until September 9th. | Read more »
Calvino Noir (Games)
Calvino Noir 1.1 Device: iOS iPhone Category: Games Price: $3.99, Version: 1.1 (iTunes) Description: The film noir stealth game. Calvino Noir is the exploratory, sneaking adventure through the 1930s European criminal underworld.... | Read more »
Angel Sword (Games)
Angel Sword 1.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.0 (iTunes) Description: Prepare to adventure in the most epic full scale multiplayer 3D RPG for mobile! Experience amazing detailed graphics in full HD.... | Read more »

Price Scanner via MacPrices.net

Big Grips Lift Handle For iPad Air and iPad A...
KEM Ventures, Inc. which pioneered the extra-large, super-protective iPad case market with the introduction of Big Grips Frame and Stand in 2011, is launching Big Grips Lift featuring a new super-... Read more
Samsung Launches Galaxy Tab S2, Its Most Powe...
Samsung Electronics America, Inc. has announced the U.S. release of the Galaxy Tab S2, its thinnest, lightest, ultra-fast tablet. Blending form and function, elegant design and multitasking power,... Read more
Tablet Screen Sizes Expanding as iPad Pro App...
Larger screen sizes are gaining favor as the tablet transforms into a productivity device, with shipments growing 185 percent year-over-year in 2015. According to a new Strategy Analytics’ Tablet... Read more
Today Only: Save US$50 on Adobe Elements 13;...
Keep the memories. lose the distractions. Summer’s winding down and it’s time to turn almost perfect shots into picture perfect memories with Elements 13. And get the power to edit both photos and... Read more
1.4GHz Mac mini on sale for $449, save $50
Best Buy has the 1.4GHz Mac mini on sale for $50 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Price for online orders only, in-store price may vary... Read more
12-inch 1.1GHz Gold MacBook on sale for $1149...
B&H Photo has the 12″ 1.1GHz Gold Retina MacBook on sale for $1149.99 including free shipping plus NY sales tax only. Their price is $150 off MSRP, and it’s the lowest price available for this... Read more
27-inch 3.3GHz 5K iMac on sale for $1849, sav...
Best Buy has the 27″ 3.3GHz 5K iMac on sale for $1849.99. Their price is $150 off MSRP, and it’s the lowest price available for this model. Choose free shipping or free local store pickup (if... Read more
Worldwide Tablet Shipments Expected to Declin...
Does Apple badly need a touchscreen convertible/hybrid laptop MacBook? Yes, judging from a new market forecast from the International Data Corporation (IDC) Worldwide Quarterly Tablet Tracker, which... Read more
Continued PC Shipment Shrinkage Expected Thro...
Worldwide PC shipments are expected to fall by -8.7 percent in 2015 and not stabilize until 2017, according to the latest International Data Corporation (IDC) Worldwide Quarterly PC Tracker data. The... Read more
Imminent iPhone 6s Announcement Leads To 103%...
NextWorth Solutions, with its online and in-store electronics trade-in programs including http://NextWorth.com, reports that it has experienced a 103 percent surge in quoted trade-in values over the... Read more

Jobs Board

*Apple* Retail Online Store: Customer Insigh...
**Job Summary** Apple Retail (Online Store) is seeking an experienced e-commerce analytics professional to join the Customer Insights Team. The Web e-Commerce Analyst Read more
*Apple* Music, Business Operations - Apple I...
Changing the world is all in a day039s work at Apple . If you love innovation, here039s your chance to make a career of it. You039ll work hard. But the job comes with Read more
WW *Apple* Retail Online Store: Customer In...
**Job Summary** The Apple Retail - Online Store is seeking an experienced web merchandising analytics professional to join the Customer Insights Team. The Web Read more
Senior Payments Security Manager - *Apple*...
**Job Summary** Apple , Inc. is looking for a highly motivated, innovative and hands-on senior payments security manager to join the Apple Pay security team. You will Read more
Software QA Engineer, *Apple* Pay Security...
**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.