TweetFollow Us on Twitter

Mar 94 Tips
Volume Number:10
Issue Number:3
Column Tag:Tips & Tidbits

Tips & Tidbits

Using GWorlds and the Pallette Manager

Edited by Scott Boyd and Neil Ticktin

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

Tip Of The Month

Studies have shown that anyone who has to focus visual attention in one place for a long time (like a computer user), will blink less often. This makes your eyes dry, and is the main cause of eyestrain. Even though blinking is a reflex action and usually outside of conscious control, there’s an easy way to increase your blink-rate.

Write the word “Blink!” on a small piece of paper. Then stick it someplace on your computer monitor where you will always be able to see it. Put one on every monitor you have. Every time you notice it, follow the instruction: Blink a couple of times, and look away from your monitor to focus on some distant object for a few seconds. Then get back to work before your boss catches you staring off into space.

You’ll notice the paper a lot at first, eventually less often. The initial effect is just to make you think about it. But even after you stop noticing it consciously, leave the note there. It has a subliminal “training” effect that makes you blink more often. It’s like tying a string around your finger to help you remember something. This really works to reduce eyestrain. But it’s so simple and inexpensive that most people don’t believe it until they’ve used it for a while.

- Lee David Rimar, Absoft Corporation

[As with all tips, consult your physician before trying this at home! - Ed. nst]

This column is your opportunity to spread the word about little bits of information that you find out about. These tidbits can be programming related or they can be user tips that are particularly useful to programmers.

MacTech Magazine will pay $25 for every tip used, and $50 for the Tip of the Month. Or you can take your award in orders or subscriptions.

To submit a tip, send in a letter to the magazine. E-mail is our preferred method, but feel free to send something via the US Mail. See page two for all addresses. If you do send snail mail, enclose a printed copy and a disk copy of the letter so that it does not have to be retyped.

Down and dirty

The following two MOVE instructions will load a zero into lower D0 on a 68000 processor and a one on 68020 or better.


/* 1 */
; Get offset to be scaled
303C 0001  Move.W  #1,D0

; Get one of the two bytes 00 or 01!
103B 02FB  Move.B  *-3(PC,D0.W*2),D0 

This is a much cheaper way than _Gestalt to find out if the 32x32 => 64 multiply instructions are available, etc. To see why this works, first consider 68020 or better hardware. After the Move.W instruction lower D0 will contain the value one. The *-3(PC) part of the Move.B addresses the 3C byte of the Move.W instruction, but indexing by D0 is also specified. Since the scaling field is two, the effective index is two times one or two. Thus the Move.B fetches the byte two down from the 3C byte, which is the 01 byte. Thus on 68020 or better hardware we get a one.

Now consider 68000 hardware. It does not implement index scaling, nor does it notice it being called for! Thus a 68000 will execute the Move.B instruction as if it were the instruction:


/* 2 */
 Move.B  *-3(PC,D0.W),D0

Now the effective index is one (not two) and the zero byte that is one down from the 3C byte is loaded. Thus on 68000 hardware we get a zero. Note also that the Zero toggle will be set on 68000 and cleared on 68020 or better hardware. This allows an immediate BZ/BEq or BNZ/BNE to be used.

The information that the 68000 processor fully decodes all 16384 possible opcode words but does not fully decode the addressing modes in extension words can be found in the Advanced Topics appendix of Motorola's MC68020 32-Bit Microprocessor User's Manual (Second Edition).

- Charles Cranston

zben@ni.umd.edu

Starting an init

I always the following code for the entry point for an INIT, WDEF or any other code resource. This template can only be used with Think C, as it uses assembly and it relies on A4 to reference globals. The 'Custom Header' must be checked in the 'Set Project Type '-dialog.


/* 3 */
void main (void) ;
void header (void) ;

void header (void)
{
  asm {
    BRA.S  @next   ; jump over the following data
    DC.L   'TMON'  ;   tell TMON todo label-searching
    DC.L   'INIT'  ;   use this and the next 4 bytes to label
    DC.L   'SPPS'  ;   this code resouce
 next:
    LEAheader, A0  ; load the address of the code resource in A0
    JMP    main  ; jump to main
  }
}

#include <SetUpA4.h>   // We need this if we have globals

void main (void)
{ Ptr  mySelf ;  // pointer to this code resource

  asm {
    move.l A0, mySelf
  }

  RememberA0()   ;  // put A0 in a save spot
  SetUpA4() ;  // and use it to set up A4
        
  RestoreA4() ;

The low-level debugger TMON looks for MacsBug labels in code resources that it knows about. If it doesn’t know the type of a resource to be code, or if it is detached and no longer a resource, TMON will not show labels in the code. The TMON User Area 'AddRange/TMON.fixed' looks for the string 'TMON' two bytes into every block it finds, and then asks TMON to scan it for labels. It was written by Ken Schalk and it is available on bulletin boards.

The following two strings mark what the block is about. This is great for debugging. If I want to set a breakpoint, I simply search for these strings in memory,

After the 'next' label, I load the address of the start of the code resource in register A0. This is required by Think C so that it can retrieve it to set A4 for accessing globals. The statements RememberA0() and SetUpA4() do the trick. Always be sure to call RestoreA4() before leaving the routine. A0 contains a pointer to the start of the block, and I save it in the variable 'mySelf'. If I want to keep the code in memory afterwards, I simply have to execute 'DetachResource(RecoverHandle(mySelf))'.

- Jan Bruyndonckx

Wave Research, Belgium

Tiny MPWScript

Here’s a tiny MPW script I find indispensible when collaborating on an MPW project. It lets you instantly open the files that your coworkers have changed.

The CheckOut command does have a -open option, but with this script you can choose which files to open and in what order, and you can wait until later to do it. Of course, once you have a file open you can use CompareRevisions to see what changed. Put this script in your MPW:Scripts folder and call it “Checked”. Opens the file referenced in the output of a projector CheckOut -p command:


/* 4 */
Checked out "HD:Blah:Blah.c,9" from "Blah ".

You can execute lines of this form directly from your worksheet (in groups or individually). This is an amazingly complicated script...not! It ignores its first argument, which is always “out”, its third argument, which is always “from”, and its fourth argument, which is the project pathname. All we care about is the second argument, which is almost the filename that we want the trick is ignoring the comma and digits at the end, which we do by matching the argument against a regular expression (see “help patterns”).


/* 5 */
(evaluate "{2}" =~ /( )®1,[0-9.]+/ ) > Dev:Null
open "{®1}"

Yes, it’s a two-line script.

- Dave Lyons

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Carbon Copy Cloner 4.1.16 - Easy-to-use...
Carbon Copy Cloner backups are better than ordinary backups. Suppose the unthinkable happens while you're under deadline to finish a project: your Mac is unresponsive and all you hear is an ominous,... Read more
Sketch 45 - Design app for UX/UI for iOS...
Sketch is an innovative and fresh look at vector drawing. Its intentionally minimalist design is based upon a drawing space of unlimited size and layers, free of palettes, panels, menus, windows, and... Read more
NeoFinder 7.1 - Catalog your external me...
NeoFinder (formerly CDFinder) rapidly organizes your data, either on external or internal disks, or any other volumes. It catalogs all your data, so you stay in control of your data archive or disk... Read more
TunnelBear 3.0.15 - Subscription-based p...
TunnelBear is a subscription-based virtual private network (VPN) service and companion app, enabling you to browse the internet privately and securely. Features Browse privately - Secure your data... Read more
Hopper Disassembler 4.2.5- - Binary disa...
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32-bit and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about... Read more
BetterTouchTool 2.261 - Customize Multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
Sketch 44.1 - Design app for UX/UI for i...
Sketch is an innovative and fresh look at vector drawing. Its intentionally minimalist design is based upon a drawing space of unlimited size and layers, free of palettes, panels, menus, windows, and... Read more
BetterTouchTool 2.260 - Customize Multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
Chromium 59.0.3071.115 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. Version 59.0.3071.115: This update has no Flash plug... Read more
SyncTwoFolders 2.2.3 - Syncs two user-sp...
SyncTwoFolders simply synchronizes two folders. It supports synchronization across mounted network drives and it is a possibility to run a simulation showing in a log what will be done. Please visit... Read more

Latest Forum Discussions

See All

Dive into epic summer adventure with Oce...
Summer may be the best time to enjoy ocean adventures, and now you don’t even have to leave the comfort of your own home, thanks to the folks at Joycity, creators of Oceans & Empires. The old-timey naval MMO is getting a sizable new June Grand... | Read more »
Missile Cards (Games)
Missile Cards 1.0.9 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.9 (iTunes) Description: "Missile Command meets Solitaire...only with more doomlasers, death, and explosions." | Read more »
Collect mini assassins in 'Assassin...
Assassin's Creed is traveling back in time to the Spanish Inquisition for its latest mobile entry, Assassin's Creed Rebellion. The game is giving the series a look that's a huge departure from its past design, recreating classic characters in a... | Read more »
Animal Crossing is still coming to mobil...
Animal Crossing is still coming to mobile in 2017, according to aWaypointinterview with Nintendo. Announced in 2016, the game was delayed without a defined release window. However, fans of Nintendo's fantasy slice of life game won't have to wait... | Read more »
Ravenscroft 275 Piano (Music)
Ravenscroft 275 Piano 1.0.0 Device: iOS Universal Category: Music Price: $35.99, Version: 1.0.0 (iTunes) Description: Experience the splendor of a Ravenscroft Grand with the most realistic sounding piano ever created for iOS. Launch... | Read more »
This War of Mine gets a new ending and m...
This War of Mine just got a big new update, featuring free DLC that adds a new ending to the game, among other exciting changes. The update is celebrating the game's two-year release anniversary. Apart from the new ending, which will be quite... | Read more »
Summon eight new heroes in Fire Emblem H...
Nintendo keeps coming at us with Fire Emblem Heroes updates, and it doesn't look like that trend is stopping anytime soon. The folks behind the game have just announced the new War of the Clerics Voting Gauntlet, expected to start next Tuesday. [... | Read more »
The best deals on the App Store this wee...
iOS publishers are pulling out all the stops this week -- there's a huge number of seriously great games at discounted prices this week. Let's not waste any time and get right down to business. [Read more] | Read more »
The House of da Vinci (Games)
The House of da Vinci 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: Enter The House of Da Vinci, a new must-try 3D puzzle adventure game. Solve mechanical puzzles, discover hidden... | Read more »
Solve the disappearance of history’s gre...
Blue Brain Games invites you to indulge in an immersive hands-on 3D puzzle adventure in similar vein to The Room series, with its debut release The House of Da Vinci. Set during the historic period of the Italian Renaissance (when Leonardo himself... | Read more »

Price Scanner via MacPrices.net

Will iPad Running iOS 11 Be The ‘Ute’ Of The...
Steve Jobs’ analogy comparing iPads and PCs to cars and trucks respectively is seven years old but still stimulates discussion and debate. Appearing on an All Things D panel in 2010 shortly after the... Read more
Free CarePassport App gives Patients control...
Boston based CarePassport is on a mission to enable patients to take control of their medical records by allowing patients to aggregate, store, share and manage all their medical data including... Read more
Western Digital Launches New My Passport Ultr...
Western Digital Corporation has expanded its WD brand My Passport portable drive line with the redesigned My Passport Ultra drive. In addition to a new metallic look, the drive offers intuitive WD... Read more
Clearance 2016 13-inch MacBook Pros available...
B&H Photo has clearance 2016 13″ MacBook Pros in stock today for up to $210 off original MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: - 13″ 2.9GHz/512GB Touch Bar... Read more
Apple Releases iOS 11 Public Beta; How To Get...
The official release of Apple’s latest mobile operating system iOS 11 is vaguely slated for the fall, but as of June 26, ordinary users can download an iOS 11 public beta. To download the iOS 11... Read more
Extend Life of MacBook Pro Retina 2.0TB With...
MacSales.com/Other World Computing has announced availability of the new OWC 2.0TB Aura Pro Solid State Drive for mid-2012 to early 2013 Apple MacBook Pro with Retina display. One of the fastest... Read more
BBEdit SummerFest 2017 Discount Ends Friday,...
You can get 20% off BBEdit for a limited time in Bare Bones Software’s http://www.eastgate.com/Tinderbox/Specials/SummerFest.html?mc_cid=f2101ca260&mc_eid=[UNIQID]SummerFest 2017 sale and... Read more
Use Apple’s Education discount to save up to...
Purchase a new Mac using Apple’s Education discount, and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free: - 15″ 2... Read more
Clearance 27-inch 3.3GHz 5K iMac available fo...
Amazon clearance 27″ 3.3GHz 5K iMacs (MK482LL/A) available for $1799.90 including free shipping. Their price is $500 off original MSRP, and it’s the lowest price available for this model from any... Read more
13-inch 1.8GHz/256GB MacBook Air on sale for...
B&H Photo has the updated 2017 13″ 1.8GHz/256GB MacBook Air (MQD42LL/A) in stock and on sale for $1129 including free shipping plus NY & NJ tax only. Their price is $70 off MSRP. Read more

Jobs Board

*Apple* News Product Marketing Mgr., Publish...
…organizational consensus on strategy and vision for publisher tools, authoring, and Apple News Format.Carries this strategy and vision across the organization to Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Security Data Analyst - *Apple* Information...
…data sources need to be collected to allow Information Security to better protect Apple employees and customers from a wide range of threats.Act as the subject matter Read more
Lead *Apple* Solutions Consultant - Apple I...
…integrity, and trust.Success Metrics/Key Performance Indicators:Quantitative* Year over Year growth in Apple Product and Beyond the Box sales in the assigned Point of Read more
*Apple* Solutions Consultant till v%u00E5r...
…ethics, integrity, and trust.Success Metrics/Key Performance Indicators:QuantitativeYear over Year growth in Apple Product and Beyond the Box sales in the assigned Point Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.