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}

INTERFACE

USES
 MemTypes,QuickDraw,OSIntf,ToolIntf;

PROCEDURE SETUPVBL;
PROCEDURE Wrap;

IMPLEMENTATION

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

BEGIN
 theCode:= Get1Resource(‘INIT’,1);
 SaveZone := GetZone;
 SetZone(SystemZone);
 
 SizeNeeded := SizeResource(theCode) - (LongInt(@SetUpVBL) - LongInt(theCode^)) 
+ SizeOf(QElem);
 ResrvMem(SizeNeeded);
 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)));
 SetZone(SaveZone);
 
 {put vbl task ptr addr into ptr where our patch will be}
 thePtr := Pointer(PatchPtr);
 thePtr^ := LongInt(myQElem);
 
 WITH theVBL DO BEGIN
 qType  := ORD(vType);
 vblAddr  := Pointer(ORD(PatchPtr)+4);
 vblCount := 6;
 vblPhase := 0;
 END;
 myQElem^.vblQElem := theVBL;
 myErr := VInstall(myQElem);
END;

PROCEDURE Wrap;
{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.
}

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

TYPE
 LPtr = ^LongInt;

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

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

END.

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.

 
AAPL
$106.98
Apple Inc.
-0.36
MSFT
$46.05
Microsoft Corpora
-0.57
GOOG
$550.31
Google Inc.
+0.98

MacTech Search:
Community Search:

Software Updates via MacUpdate

Cocktail 8.0.1 - General maintenance and...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
LibreOffice 4.3.3.2 - Free Open Source o...
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
VMware Fusion 7.0.1 - Run Windows apps a...
VMware Fusion allows you to create a Virtual Machine on your Mac and run Windows (including Windows 8.1) and Windows software on your Mac. Run your favorite Windows applications alongside Mac... Read more
OneNote 15.3.2 - Free digital notebook f...
OneNote is your very own digital notebook. With OneNote, you can capture that flash of genius, that moment of inspiration, or that list of errands that's too important to forget. Whether you're at... Read more
Audio Hijack Pro 2.11.4 - Record and enh...
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 with Audio Hijack... Read more
Iridient Developer 3.0.0 beta 3 - Powerf...
Iridient Developer (was RAW Developer) is a powerful image conversion application designed specifically for OS X. Iridient Developer gives advanced photographers total control over every aspect of... Read more
TextWrangler 4.5.11 - Free general purpo...
TextWrangler is the powerful general purpose text editor, and Unix and server administrator's tool. Oh, and also, like the best things in life, it's free. TextWrangler is the "little brother" to... Read more
NeoFinder 6.6 - 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
Chromium 38.0.2125.111 - 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. FreeSMUG-Free OpenSource Mac User Group build is... Read more
Default Folder X 4.6.11 - Enhances Open...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click... Read more

Latest Forum Discussions

See All

Audio Defence : Zombie Arena (Games)
Audio Defence : Zombie Arena 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: A zombie shooter audio game. Made from gut-wrenching 3D binaural sound, for a new kind of weird immersion. You... | Read more »
RPG Asdivine Hearts (Games)
RPG Asdivine Hearts 1.1.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.1.0 (iTunes) Description: SPECIAL PRICE50% OFF (USD 7.99 -> USD 3.99)!!! Travel alongside four companions and a cat in the adventure of a... | Read more »
Haunt the House: Terrortown (Games)
Haunt the House: Terrortown 1.0.1 Device: iOS Universal Category: Games Price: $.99, Version: 1.0.1 (iTunes) Description: 66.6% OFF! SPECIAL SPOOKY HALLOWEEN LAUNCH PRICE! 66.6% OFF! ...What was that sound? Is somebody there? | Read more »
SAS: Zombie Assault 4 Review
SAS: Zombie Assault 4 Review By Jennifer Allen on October 30th, 2014 Our Rating: :: FLAWED SHOOTERUniversal App - Designed for iPhone and iPad Shoot everything that moves in this fun, if flawed, twin-stick shooter.   | Read more »
Naailde the Witch Review
Naailde the Witch Review By Amy Solomon on October 30th, 2014 Our Rating: :: PITCH-PERFECT STORYTELLINGUniversal App - Designed for iPhone and iPad Marvelous storytelling, narration, and moving illustrations make this storybook... | Read more »
1st & Goal Review
1st & Goal Review By Andrew Fisher on October 30th, 2014 Our Rating: :: FOR THE D&D LOVING QBUniversal App - Designed for iPhone and iPad 1st & Goal is a board gamer’s football game, a football fan’s board game, and... | Read more »
French Developer Pated Unveils Seashine
French Developer Pated Unveils Seashine Posted by Ellis Spice on October 30th, 2014 [ permalink ] French one-man studio Pated has unveiled Seashine, “a poetic journey into the abyss.” Players take on the role of a jellyfish strugglin | Read more »
Agents of Storm: Tips, Tricks, and Strat...
Calling all agents: Would you like to see what we thought of this rather pretty base builder? Check out our Agents of Storm review! Have you downloaded Agents of Storm, been bowled over by the graphics, and aren’t quite sure what to do next? Never... | Read more »
Any.DO 2.0 Hopes to Help Manage Producti...
Any.DO 2.0 Hopes to Help Manage Productivity Posted by Ellis Spice on October 30th, 2014 [ permalink ] iPhone App - Designed for the iPhone, compatible with the iPad | Read more »
Base Busters Review
Base Busters Review By Jennifer Allen on October 30th, 2014 Our Rating: :: FUN BUT RESTRICTED MIXUniversal App - Designed for iPhone and iPad Mixing up two forms of tower defense gaming and collectible cards, Base Busters is a fun... | Read more »

Price Scanner via MacPrices.net

Apple Regains Momentum As Windows Stutters An...
The latest smartphone sales data from Kantar Worldpanel ComTech, for the three months to March 2014, shows Apple performing strongly in the first quarter of the year, with sales bouncing back in... Read more
Worldwide Smartphone Shipments Increase 25.2%...
New smartphone releases and an increased emphasis on emerging markets drove global smartphone shipments above 300 million units for the second consecutive quarter, according to preliminary data from... Read more
Apple now offering refurbished 2014 15-inch M...
The Apple Store is now offering Apple Certified Refurbished 2014 15″ Retina MacBook Pros for up to $400 off the cost of new models. An Apple one-year warranty is included with each model, and... Read more
Apple drops prices on refurbished 2013 Retina...
The Apple Store has dropped prices on 2013 Apple Certified Refurbished 13″ and 15″ Retina MacBook Pros, with Retina models now available starting at $999. Apple’s one-year warranty is standard, and... Read more
New 2.8GHz Mac mini on sale for $949, save $5...
Abt Electronics has the new 2.8GHz Mac mini in stock and on sale for $949.05 including free shipping. Their price is $50 off MSRP, and it’s the lowest price available for this model from any reseller... Read more
Sale! 3.7GHz Quad Core Mac Pro available for...
 B&H Photo has the 3.7GHz Quad Core Mac Pro on sale for $2649 including free shipping plus NY sales tax only. Their price is $350 off MSRP, and it’s the lowest price for this model from any... Read more
Mujjo Steps Up The Game With Refined Touchscr...
Netherlands based Mujjo have just launched their Refined Touchscreen Gloves, stepping up their game. The gloves feature a updated elegant design that takes these knitted gloves to the next level. A... Read more
Sale! Preorder the new 27-inch 5K iMac for $2...
 Abt Electronics has the new 27″ 3.5GHz 5K iMac on sale and available for preorder for $2374.05 including free shipping. Their price is $125 off MSRP, and it’s the lowest price available for this... Read more
Simplex Solutions Inc. Brings Secure Web Surf...
New York based Simplex Solutions Inc. has announced the release and immediate availability of Private Browser 1.0, its revolutionary new secure web browser developed for iPhone, iPad and iPod touch... Read more
Save up to $180 off MSRP with an Apple refurb...
The Apple Store has Apple Certified Refurbished 2014 MacBook Airs available for up to $180 off the cost of new models. An Apple one-year warranty is included with each MacBook, and shipping is free.... Read more

Jobs Board

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
Sr. Manager, *Apple* Deployment Programs fo...
**Job Summary** Apple is seeking candidates for a new position on the Education Content and Technology team. iPad and Mac is in the hands of millions of teachers and Read more
*Apple* Solutions Consultant (ASC) - Apple I...
…important role that the ASC serves is that of providing an excellent Apple Customer Experience. Responsibilities include: * Promoting Apple products and solutions Read more
*Apple* Solutions Consultant (ASC) - Apple I...
…important role that the ASC serves is that of providing an excellent Apple Customer Experience. Responsibilities include: * Promoting Apple products and solutions Read more
*Apple* Solutions Consultant (ASC) - Apple I...
…important role that the ASC serves is that of providing an excellent Apple Customer Experience. Responsibilities include: * Promoting Apple products and solutions Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.