TweetFollow Us on Twitter

Jan 90 Letters
Volume Number:6
Issue Number:1
Column Tag:Letters

INITs First

By David E. Smith, Editor & Publisher, MacTutor

INITs in Pascal or C

Steve Brecher

Sunnyvale, CA

There are some problems in the advice and code provided in the October 1989 issue’s Pascal Procedures and C Workshop, which discuss writing INITs in the respective languages.

The VBL task shown in Pascal Procedures calls GetGDevice without checking whether Color QuickDraw is available. It assumes that the current GDevice is the monitor the mouse is on. Multiple-monitor users may be surprised to find the mouse jumping from the middle of one monitor to the opposite edge of another when they press Option for some application purpose. The code also assumes, in its reference to QuickDraw globals through CurrentA5, that QuickDraw has been initialized for the currently executing application. This is not necessarily true.

The following comments apply to the C Workshop article.

The author does not understand the function of the ioNamePtr field in File Manager parameter blocks. This field contains either a pointer to a caller- allocated string buffer or nil if the caller chooses not to pass or receive a filename string. The File Manager does not allocate a string buffer for the caller.

INIT 31 does not necessarily expand the system heap by the amount specified in your ‘sysz’ 0 resource, and it certainly does not “collapse” the heap to undo any previous expansions--CompactMem collects free blocks together; it does not shrink a heap. What INIT 31 does is expand the system heap if necessary to assure that a contiguous block of the size specified in the ‘sysz’ 0 resource is available at the time the first (and usually only) INIT resource in an INIT/

cdev/RDEV is executed. Any space gained by heap expansion that is not used by the INIT will remain free when the INIT exits--but may be sopped up by subsequent INITs or system activity.

The author unduly discounts the dangers of tail patching. A tail patch is a trap patch that calls (JSRs to) the original patch instead of JMPing to it. A tail patch may nullify an Apple-supplied ROM code patch. Such Apple patches operate by comparing their return address on the stack with certain hard-coded ROM addresses. By JSRing to the original trap code, one assures that such a comparison will always fail since the Apple patch will see one’s own return address rather than that of the original trap caller. In some cases tail patching is necessary; my own products do it. But one should at least check the latest System release to make sure that one’s tail patches do not nullify ROM code patches. And in some cases one can eat one’s cake and have it too by JSRing to the original trap code, doing necessary post-processing, and then JMPing to the original code. The original code will be executed twice, and the second execution will invoke any ROM patch code that may be installed. The JMP requires assembly language.

The example INIT ignores the fact that Resource Manager traps preserve all registers except D0/A0 (except LoadResource, which preserves all including D0/A0)--IM I-113. It also uses the Dialog Manager with no assurance that it has been intialized, not to mention QuickDraw, etc.

Writing Inits in Pascal

Roland van Straten

Dutch Macintosh Developer

Perhaps this is not the right way to inform you about bugs, but sending a letter takes a while and it has no way to send real program listings. So if this is not the way you prefer, let me know.

I’ve read the article about “Writing INITs in Pascal”, MacTutor Oct 89, Page 51, and after some study of the source code I noticed two bugs. Maybe Steve Kiene’s system and/or compiler do something special or he forgot to test it, I don’t know.

1. The MTemp location has a counterpart: RawMouse. It’s the next LongInt in Low Memory. If RawMouse is equal to MTemp the mouse handler will think the move has to be made absolute. Otherwise the move will be treated as relative (Steve Kiene’s program).

2. The CrsrNew location is a Byte value. Steve Kiene’s program declares a pointer to a Byte (^Byte). This is a two byte value. Look at IM vol1, pag 86. In order to fix this I used a standard type Ptr (^SignedByte) and exchanged $FF for -1.

Apart from these little bugs I enjoyed the article very much and found it useful. The article appeared at the time I was writing a VBL task that moves the mouse “outside” the screen (don’t ask me for the reason of this).

UNIT CursorWrap;

{MacTutor ©1989, issue October 1989, page 51, “Writing INITs in Pascal” 
by Steve Kiene}

{MPW 3.0 version - October 1989 - ROLAnd van Straten - ALink HOL0027}





 theVBL : VBLTask;
 myQElem: QElemPtr;
 myErr  : OSErr;
 SaveZone : THz;
 PatchPtr : Ptr;
 theCode: Handle;
 thePtr : ^LongInt;

 theCode:= Get1Resource(‘INIT’,1);
 SaveZone := GetZone;
 SizeNeeded := SizeResource(theCode) - (LongInt(@SetUpVBL) - LongInt(theCode^)) 
+ SizeOf(QElem);
 IF MemError <> NoErr THEN BEGIN
 SysBeep(1); SetZone(SaveZone); Exit(SetUpVBL); END;
 PatchPtr := NewPtr(SizeNeeded + 4) ;{get ptr for our code}
 BlockMove(@Wrap, Pointer(ORD(PatchPtr)+4), SizeNeeded);
 myQElem := QElemPtr(NewPtr(SizeOf(QElem)));
 {put vbl task ptr addr into ptr where our patch will be}
 thePtr := Pointer(PatchPtr);
 thePtr^ := LongInt(myQElem);
 qType  := ORD(vType);
 vblAddr  := Pointer(ORD(PatchPtr)+4);
 vblCount := 6;
 vblPhase := 0;
 myQElem^.vblQElem := theVBL;
 myErr := VInstall(myQElem);

{Wrap cursor when option key is down

 MTemp  has latest mouse value
 RawMouse has the un-jerked mouse value
 CrsrNew  must be set to “-1” to indentify “moved”
 If MTemp and RawMouse are different there only will be a relative change 
of the mouse position. This looks like unstable moves on the screen. 
 Fixed this bug by moving RawMouse into the arena.
 CrsrNew is a byte. The used pointer type was a ^Byte. This is in fact 
a two byte value (WRONG). Look in IM.1 pag 68 for details on this. So 
in order to fix this use the standard Ptr type and put the value -1 into 
the addressed byte.

 CurrentA5 = $904;
 MTemp  = $828;  {Low-level interrupt mouse location [long]}
 RawMouse = $82C; {un-jerked mouse coordinates [long]}
 CrsrNew= $8CE; {Cursor changed? [byte]}
 OptionKey= 58;

 LPtr = ^LongInt;

 myQElem: QElemPtr;
 currGDevice: GDHandle;
 theMap : KeyMap;
 changed: Boolean;
 myRectPtr: ^Rect;
 mouseRect, myRect : Rect;
 myPtr,myPtr2    : LPtr;
 PPtr,P2Ptr : ^Point;

 IF theMap[OptionKey] THEN BEGIN
 changed := FALSE;
 currGDevice :=GetGDevice;
 IF currGDevice <> NIL THEN
 mouseRect := currGDevice^^.gdRect
 BEGIN {use A5 to get offset to screenbits.bounds}
 myPtr  := Pointer(CurrentA5);
 myPtr2 := Pointer(myPtr^);
 myRectPtr := Pointer(myPtr2^-116);
 mouseRect := myRectPtr^;
 PPtr := Pointer(MTemp); P2Ptr := Pointer(RawMouse);
 IF PPtr^.v <= THEN BEGIN {check cursor pos for wrap}
 PPtr^.v  := mouseRect.bottom -1;
 P2Ptr^.v := mouseRect.bottom -1;
 changed  := TRUE; END
 IF PPtr^.v >= mouseRect.bottom THEN BEGIN
 PPtr^.v  := +1;
 P2Ptr^.v := +1;
 changed  := TRUE; END
 IF PPtr^.h <= mouseRect.left THEN BEGIN
 PPtr^.h  := mouseRect.right -1;
 P2Ptr^.h := mouseRect.right -1;
 changed  := TRUE; END
 IF PPtr^.h >= mouseRect.right THEN BEGIN
 PPtr^.h  := mouseRect.left +1;
 P2Ptr^.h := mouseRect.left +1;
 changed:= TRUE; END;
 IF changed THEN 
 Ptr(CrsrNew)^ := -1;{cursor has changed}
 myQElem := QElemPtr(LPtr(Pointer(ORD(@Wrap)-4))^);      {get ptr to 
vbl task, and reset it}
 myQElem^.vblQElem.vblCount := 6;


INIT Inhibition

David Dunham

Seattle, WA

Just a quick note about Peter Hoddie’s article on INITs. He suggests that INITs not install themselves when the mouse button is down.

In fact, there is a fairly standard method of inhibiting INITs: the shift key. Not all INITs use this, but probably half the ones I’m familiar with do. My own INITs also disable themselves when their initial letter (e.g. ‘f’ for Findswell) is held at boot time.

The problem with using the mouse button is that it instructs the Mac to eject the internal disk at boot time. Disabling INITs shouldn’t be a matter of timing just when to click the mouse.


Community Search:
MacTech Search:

Software Updates via MacUpdate

ForeverSave 2.1.4 - Universal auto-save...
ForeverSave auto-saves all documents you're working on while simultaneously doing backup versioning in the background. Lost data can be quickly restored at any time. Losing data, caused by... Read more
AirPort Utility 6.3.6 - Set up and manag...
Note: Most recent release available only within OS X 10.11 El Capitan update. Use AirPort Utility to set up and manage your Wi-Fi network and AirPort base stations, including AirPort Express, AirPort... Read more
Quicksilver 1.3.1 - Application launcher...
Quicksilver is a light, fast and free Mac application that gives you the power to control your Mac with keystrokes alone. Quicksilver allows you to find what you need quickly and easily, then act... Read more
Tidy Up (Five Users) 4.1.5 - Find duplic...
Tidy Up is a complete duplicate finder and disk-tidiness utility. With Tidy Up you can search for duplicate files and packages by the owner application, content, type, creator, extension, time... Read more
Mellel 3.4.3 - The word processor of cho...
Mellel is the leading word processor for OS X and has been widely considered the industry standard since its inception. Mellel focuses on writers and scholars for technical writing and multilingual... Read more
Skype - Voice-over-internet p...
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
Bookends 12.6.0 - 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
Apple iBooks Author 2.4 - Create and pub...
Apple iBooks Author helps you create and publish amazing Multi-Touch books for iPad. Now anyone can create stunning iBooks textbooks, cookbooks, history books, picture books, and more for iPad. All... Read more
Web Snapper 3.3.9 - Capture entire Web p...
Web Snapper lets you capture Web pages exactly as they appear in your browser. You can send them to a file as images or vector-based, multi-page PDFs. It captures the whole Web page - eliminating the... Read more
Tunnelblick 3.6beta10 - GUI for OpenVPN...
Tunnelblick is a free, open source graphic user interface for OpenVPN on OS X. It provides easy control of OpenVPN client and/or server connections. It comes as a ready-to-use application with all... Read more

Camel Up (Games)
Camel Up 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: | Read more »
The Martian: Bring Him Home (Games)
The Martian: Bring Him Home 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Based on the best selling novel and critically acclaimed film, THE MARTIAN tells the story of Astronaut Mark... | Read more »
This Week at 148Apps: September 21-30, 2...
Leap Into Fall With 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 above... | Read more »
Tweetbot 4 for Twitter (Social Networki...
Tweetbot 4 for Twitter 4.0 Device: iOS Universal Category: Social Networking Price: $4.99, Version: 4.0 (iTunes) Description: *** 50% off for a limited time. *** | Read more »
Mori (Games)
Mori 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Stop, rewind and unwind with Mori. Time is always running, take a moment to take control. Mori is an action puzzle game about infinitely... | Read more »
100 Years' War (Games)
100 Years' War 1.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: | Read more »
Tower in the Sky (Games)
Tower in the Sky 0.0.60 Device: iOS Universal Category: Games Price: $1.99, Version: 0.0.60 (iTunes) Description: | Read more »
hocus. (Games)
hocus. 1.0.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0.0 (iTunes) Description: New, polished, mind-bending, minimal puzzle game with dozens of levels and extra-ordinary design Features:- Beautifully crafted... | Read more »
Mos Speedrun 2 (Games)
Mos Speedrun 2 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Mos is back, in her biggest and most exciting adventure ever! Wall-jump to victory through 30 mysterious, action packed levels... | Read more »
3D Touch could be a game-changer, but it...
Were you one of the lucky/financially secure enough ones to buy a new iPhone 6s or iPhone 6s Plus over the weekend? Yup, me too (I’m not convinced I was either of those two things, but let’s go with lucky for now), so I thought I’d delve into just... | Read more »

Price Scanner via

Apple offering refurbished 2015 13-inch Retin...
Apple is offering Certified Refurbished 2015 13″ Retina MacBook Pros for up to $270 (15%) off the cost of new models. An Apple one-year warranty is included with each model, and shipping is free: -... Read more
Apple refurbished 2015 MacBook Airs available...
Apple has Certified Refurbished 2015 11″ and 13″ MacBook Airs (the latest models), available for up to $180 off the cost of new models. An Apple one-year warranty is included with each MacBook, and... Read more
Adobe Photoshop Elements 14 Gets Haze Removal...
The latest iteration of Adobe’s powerful consumer image editing appliction Photoshop Elements 14 analyzes your photo and removes background haze, so your shot looks sharp all the way to the horizon... Read more
Apple refurbished 15-inch Retina MacBook Pros...
Apple has Certified Refurbished 2015 15″ Retina MacBook Pros available for up to $380 off the cost of new models. An Apple one-year warranty is included with each model, and shipping is free: - 15″ 2... Read more
21-inch iMacs on sale for up to $120 off MSRP
B&H Photo has 21″ iMacs on sale for up to $100 off MSRP including free shipping plus NY sales tax only: - 21″ 1.4GHz iMac: $1029.99 $70 off - 21″ 2.7GHz iMac: $1229 $70 off - 21″ 2.9GHz iMac: $... Read more
Bare Bones Software Releases TextWrangler 5.0...
Bare Bones Software has announced the release and immediate availability of TextWrangler 5.0, a major upgrade to its free, high performance, general purpose text editor for Mac OS X. Built on a new,... Read more
Apple refurbished iPad Air 2s available for u...
Apple has 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 Wi-Fi iPad Air 2... Read more
Save up to $100 on Mac AppleCare Protection P...
Adorama has 3-Year AppleCare Warranties on sale for up to $100 off MSRP including free shipping plus NY & NJ sales tax only: - Mac Laptops 15″ and Above: $249 $100 off MSRP - Mac Laptops 13″ and... 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
27-inch 3.5GHz 5K iMac on sale for $81 off MS...
Adorama has the 27″ 3.5GHz 5K iMac on sale for $2218.99, $81 off MSRP, including a free copy of Apple’s 3-Year AppleCare Protection Plan, plus a free external DVD/CD drive, and a copy of Corel... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, you're Read more
Senior Payments Architect - *Apple* Pay - A...
**Job Summary** Apple , Inc. is looking for a highly motivated, innovative and hands-on senior payments architect to join the Apple Pay Engineering team. You will Read more
SW QA Engineer - *Apple* TV - Apple (United...
**Job Summary** The Apple TV team is looking for experienced Quality Assurance Engineers with a passion for delivering first in class home entertainment solutions. **Key Read more
Finance Manager, *Apple* Online Store - App...
…successful global retailer. Innovate and think creatively as a finance partner for the Apple Online Store team. Look ahead and anticipate the needs of your business. Read more
*Apple* Retail for Business Support Supervis...
…is looking for a motivated, outgoing, and creative individual who wants to offer Apple Business Customers an unparalleled customer experience. The Apple Retail for Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.