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

Vienna 3.0.6 :5eaf312: - RSS and Atom ne...
Vienna is a freeware and Open-Source RSS/Atom newsreader with article storage and management via a SQLite database, written in Objective-C and Cocoa, for the OS X operating system. It provides... Read more
Kodi 15.1.rc1 - Powerful media center to...
Kodi (was XBMC) is an award-winning free and open-source (GPL) software media player and entertainment hub that can be installed on Linux, OS X, Windows, iOS, and Android, featuring a 10-foot user... Read more
Bookends 12.5.8 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Access the power of Bookends directly from Mellel, Nisus Writer Pro, or MS Word (... Read more
Chromium 44.0.2403.125 - 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 44.0.2403.125: This release contains a number... Read more
iMazing 1.2.2 - Complete iOS device mana...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
Audio Hijack 3.2.0 - Record and enhance...
Audio Hijack (was Audio Hijack Pro) drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio... Read more
FontExplorer X Pro 5.0.1 - Font manageme...
FontExplorer X Pro is optimized for professional use; it's the solution that gives you the power you need to manage all your fonts. Now you can more easily manage, activate and organize your... Read more
Calcbot 1.0.2 - Intelligent calculator a...
Calcbot is an intelligent calculator and unit converter for the rest of us. Featuring an easy-to-read history tape, expression view, intuitive conversion, and much more! Features History Tape -... Read more
MTR 5.0.0.1 - The Mac's oldest and...
MTR (was MacTheRipper)--the Mac's oldest and smartest DVD-backup app--is now updated to version 5.001 MTR -- the complete toolbox, not a one-trick, point-and-click extractor. MTR is intended for... Read more
LibreOffice 4.4.5.2 - 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

Card King: Dragon Wars - Tips, Tricks an...
[Read more] | Read more »
Pac-Man Championship Edition DX has brou...
Bandai Namco has released Pac-Man Championship Edition DX on iOS and Android, which features the classic arcade gameplay that we've all grown to love. Pac-Man Championship Edition DX can be enjoyed in much shorter bursts than the arcade versions... | Read more »
Cosmonautica (Games)
Cosmonautica 1.1 Device: iOS Universal Category: Games Price: $6.99, Version: 1.1 (iTunes) Description: Cast off! Are you ready for some hilarious adventures in outer space? | Read more »
Rescue humanity from a Demon horde in An...
Angel Stone is Fincon's follow up to the massively successful Hello Hero and is out now on iOS and Android. You play as a member of The Resistance, a group of mighty human warriors who have risen up in defiance of the Demon horde threatening to... | Read more »
Gallery Doctor (Photography)
Gallery Doctor 1.0 Device: iOS iPhone Category: Photography Price: $2.99, Version: 1.0 (iTunes) Description: Free up valuable iCloud and iPhone storage with Gallery Doctor, the only iPhone cleaner that automatically identifies the... | Read more »
You Against Me (Games)
You Against Me 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: A simple game… You. Me. Claim, steal, lock, score, win! | Read more »
Yep, it's True - Angry Birds 2 is O...
The not exactly rumors were true and the birds are back. Angry Birds 2 has come to the App Store and the world will... well I suppose it'll still be the same, but now we have more bird-flinging options! [Read more] | Read more »
You Could Design Your Own Card for Chain...
If you've ever wanted to create your own item, weapon, trap, or even monster for Chainsaw Warrior: Lords of the Night, this is your chance. Auroch Digital is currently holding a contest so that fans can fight to the death (not really) to see which... | Read more »
Bitcoin Billionaire is Going Back in Tim...
If you thought you managed to buy everything there is to buy in Bitcoin Billionaire and make all the money, well you though wrong. Those of you who made it far enough might remember investing in time travel - and it looks like that investment is... | Read more »
Domino Drop (Games)
Domino Drop 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Domino Drop is a delightful new puzzle game with dominos and gravity!Learn how to play it in a minute, master it day by day.Your... | Read more »

Price Scanner via MacPrices.net

11-inch MacBook Airs on sale for $100 off MSR...
Best Buy has 11-inch MacBook Airs on sale for $100 off MSRP. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store prices may vary: - 11″ 1.6GHz... Read more
iPad Air 2 on sale for up to $100 off MSRP
Best Buy has iPad Air 2s 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 available for online... Read more
Sale! 13-inch MacBook Pros on sale for $100 o...
B&H Photo has 13″ MacBook Pros on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.5GHz/500GB MacBook Pro: $999.99 save $100 - 13″ 2.7GHz/128GB Retina... Read more
Sale! Save $100 on 13-inch MacBook Airs this...
B&H Photo has the 13″ 1.6GHz/128GB MacBook Air on sale for $899.99 including free shipping plus NY tax only. Their price is $100 off MSRP, and it’s the lowest price available for this model.... Read more
Worldwide Tablet Market Decline Continues, Ap...
The worldwide tablet market declined -7.0% year-over-year in the second quarter of 2015 (2Q15) with shipments totaling 44.7 million units according to preliminary data from the International Data... Read more
TP-LINK TL-PA8030P KIT Powerline Featuring Ho...
Consumer and business networking products provider TP-LINK is now shipping its TL-PA8030P KIT AV1200 3-Port Gigabit Passthrough Powerline Starter Kit that expands your home’s network over its... Read more
Apple refurbished iPad Air 2s available for u...
The Apple Store has Apple Certified Refurbished iPad Air 2s available for up to $140 off the price of new models. Apple’s one-year warranty is included with each model, and shipping is free: - 128GB... Read more
Updated Apple iPad Price Trackers
We’ve updated our iPad Air Price Tracker and our iPad mini Price Tracker with the latest information on prices and availability from Apple and other resellers. Read more
Apple refurbished 2014 13-inch 128GB MacBook...
The Apple Store has Apple Certified Refurbished 2014 13″ MacBook Airs available starting at $759. An Apple one-year warranty is included with each MacBook, and shipping is free: - 13″ 1.4GHz/128GB... Read more
Apple’s Education discount saves up to $300 o...
Purchase a new Mac or iPad 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,... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Infrastructure Engineer - *Apple* /Mac - Hil...
Infrastructure Engineer - Apple /Mac Job Code: 1608 # of openings: 1 Description Our fortune 500 client is looking to hire an experienced Infrastructure Engineer to join Read more
Executive Administrative Assistant, *Apple*...
…supporting presentation development for senior leadership. * User experience with Apple hardware and software is preferred. Additional Requirements The following list Read more
*Apple* Bus Company is now hirin - Apple Bus...
Apple Bus Company is now hiring school bus drivers in the Pettis County area. Class B CDL preferred. Free training provided. No nights or weekends required. Flexible Read more
*Apple* Certified Mac Technician - Updated 6...
…and friendly, hands-on technical support to customers troubleshooting and repairing Apple /Mac products with courtesy, speed and skill. Use your problem-solving skills Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.