TweetFollow Us on Twitter

Cursor Wrap
Volume Number:5
Issue Number:0
Column Tag:Pascal Procedures

Related Info: Control Panel OS Utilities

Writing INITs in Pascal

By Steve Kiene, Lincoln, NE

Why Inits: Trap Patching, etc

INITs are pretty hot items these days. I have at least six in my System Folder and I know people that have fifteen or more. INITs do anything from making it easier to move through SFGetFiles (SFScrollINIT by Andy Hertzfeld) to creating large virtual desktops (SteppingOUT II). INITs are used to customize the Macintosh. They are very simple to install and remove (dragging them into or out of the System Folder).

The majority of INITs trap patches. Patch trapping is simply the rewriting of the Macintosh’s internal routines or the modification of these routines for special situations. This is done by using the traps GetTrapAddress,SetTrapAddress, NSetTrapAddress, and NGetTrapAddress. Usually the programmer calls GetTrapAddress and saves the address for later use; the programmer then puts this address somewhere,usually in his/her code so that his/her code can check for the special situation, do whatever-taken that it is the special situation, and then call the original trap address. All trap patches should call the original trap address; this allows traps to be patched more than one time and is the best bet for compatibility insurance.

I would guess that 90% of all INITs are written in assembly. I’m sure they probably say that INITs are much easier to write in assembly. Well, it’s probably true, if you know assembly, but, if you don’t know assembly, I would say that it isn’t all that easy. This article, since it is in the Pascal section, demonstrates how to write an INIT in Pascal, includes full source to an INIT that allows the cursor to wrap around the screen, and gives a couple of hints on writing INITs in general.

Having the INIT install our patch.

INITs must load their code into the system heap so that the code will stay around as application’s are launched (the application heap is flushed every launch or return to the Finder). The INIT part of the code should put the trap patch or whatever code into the system heap. In CursorWrap, the included INIT, we create a pointer in the system heap that is four bytes greater than the size of our VBL task code; we then BlockMove the code into the pointer starting at the location of the pointer plus four. We store the pointer to our VBL task in the four bytes before our code so that we have easy access to it. The code is written in MPW Pascal, but should be easy to convert to any other development system.

{1}

Unit CursorWrap;
Interface
Uses
 {$LOAD MAC.Dump}
 MemTypes,QuickDraw,OSIntf,Toolintf,PackIntf,Script;
Procedure SetUpVBL;
Procedure Wrap;

Implementation
Procedure SetUpVBL;
var
 theVBL : VBLTask;
 myQElem: QElemPtr;
 myErr  : OSErr;
 SaveZone : THz;
 SizeNeeded : Longint;
 PatchPtr : Ptr;
 theCode: Handle;
 thePtr : ^LongInt;
 dummyErr : OSErr;
Begin
 { * Get handle to our code *}
 theCode:=Get1Resource(‘INIT’,1);
 { * Use the system’s Heap * }
 SaveZone:=GetZone;
 SetZone(SystemZone);
 { * Get size of our patch code and our QElem ptr * }
 SizeNeeded:=SizeResource(theCode)-(LongInt(@SetUpVBL)-LongInt(theCode^))+sizeof(QElem);
 ResrvMem(SizeNeeded);
 If MemError<>NoErr then
 begin
 { * If not enough room in system heap then get out * }
 SysBeep(1);
 SetZone(SaveZone);
 exit(SetUpVBL);
 end;
 { * Get new ptr for our code * }
 PatchPtr:=NewPtr(SizeNeeded+4);
 { * blockmove our code in * }
 BlockMove(@Wrap,Pointer(Ord(PatchPtr)+4),SizeNeeded);
 { * get new ptr for our VBL task * }
 myQElem:=QElemPtr(NewPtr(sizeof(QElem)));
 { * restore zone * }
 SetZone(SaveZone);
 { * put our vbl task ptr’s address into the ptr where our patch code 
will be * }
 thePtr:=Pointer(PatchPtr);
 thePtr^:=LongInt(myQElem);
 { * set up VBL and install * }
 with theVBL do
 begin
 qType:=Ord(vType);
 vblAddr:=Pointer(Ord(PatchPtr)+4);
 vblCount:=6;
 vblPhase:=0;
 end;
 myQElem^.vblQElem:=theVBL;
 dummyErr:=VInstall(myQElem);
End;
{------------------------------------------------------}
Procedure Wrap;
{**
This code allows the cursor to seemly wrap around the screen when the 
<Option> key is held down.  It checks the low level interupt mouse location 
(mTemp) and if it is on one edge of the screen it moves it to the the 
other edge.  It puts the new cursor cooridinate into mTemp and then puts 
$FF into cursorNew--this tells the cursor routines that the cursor has 
moved 
**}
const
 CurrentA5= $904;
var
 myQElem: QElemPtr;
 thePtr : ^LongInt;
 CursorCoordPtr  : ^Point;
 ChangedPtr : ^Byte;
 changed: Boolean;
 theMap : KeyMap;
 currGDevice: GDHandle;
 mouseRect: Rect;
 myRectPtr: ^Rect;
 myPtr,myPtr2    : ^longint;
 myRect : Rect;
Begin
 { * Get the keymap and check if option down; if is not then do not allow 
wrap * }
 GetKeys(theMap);
 If theMap[58] then
 Begin
 { * set up ptr to low memory global of cursor location * }
 CursorCoordPtr:=Pointer($828);
 changed:=false;
 { * get rectangle of screen * }
 currGDevice:=GetGDevice;
 If currGDevice<>Nil then
 mouseRect:=currGDevice^^.gdRect
 else
 begin
 { * Use currentA5 to get offset to screenBits.bounds * }
 myPtr:=pointer(CurrentA5);
 myPtr2:=pointer(myPtr^);
 myRectPtr:=Pointer(myPtr2^-116);
 mouseRect:=myRectPtr^;
 end;
 InsetRect(mouseRect,1,1);
 { * check cursor location and change it if wrapping * }
 With CursorCoordPtr^,mouseRect do
 Begin
 if v<=top then
 Begin
 v:=bottom-1;
 changed:=true;
 End
 else if v>=bottom then
 Begin
 v:=top+1;
 changed:=true;
 End;
 if h<=left then
 Begin
 h:=right-1;
 changed:=true;
 End
 else if h>=right then
 Begin
 h:=left+1;
 changed:=true;
 End;
 End;
 { * if we changed the cursor location then set the low memory global 
cursorNew * }
 If changed then
 Begin
 changedPtr:=Pointer($8CE);
 { * this tells the cursor drawing routines that the cursor is moved 
* }
 changedPtr^:=$FF;
 End;
 End;
 { * get ptr to VBL taks from where we originally put it * }
 thePtr:=Pointer(Ord(@Wrap)-4);
 { * reset the vblcount so that we are executed again * }
 myQElem:=QElemPtr(thePtr^);
 myQElem^.vblQElem.vblCount:=6;
End;
End.

Another Way

There is another way to store variables. In our example INIT this would be the VBL pointer address. This way involves using a header file that is written in assembler. The header file does nothing but branch over instructions that take up space. The header would look something like the following in MPW assembly:

Header  MAIN EXPORT

Header1
 BRA.S  @1
 DC.L 0
 DC.L 0
 DC.L 0
@1
 END

This header would leave room for twelve bytes, three handles, or whatever. To use this you would have to link the Header.a.o in first and reference it in you pascal code. A little help:

{3}

Procedure Header; EXTERNAL;{must be after Implementation }
myPtr:=Ptr(Ord(@Header)+2); { myPtr points to the first byte of storage 
}

The above statement returns a pointer to the address of the header plus two bytes, so that we skip over the branch statement.

You would use this type of code when you are writing a WDEF, CDEF, etc. and you want to have some type of communication between your patches and your custom definition. We used this type of code when we wrote Tear-Off Menus and wanted our custom WDEF and MDEF to be able to access globals that our Menu and Window Manager traps used.

Added tips for coping with problems.

When writing INITs that are a little heavier than a ‘one trap patch’ INIT or a simple VBL installation, then you are most likely going to run into problems with certain programs. Maybe it will be because the guys at Microsoft didn’t quite follow all of the rules or perhaps it’s some other reason. Regardless the problem, the answer is to not install when you know you are not compatible. The easiest way to do this is to try and load the resource type of the creator type (ie. MSWD for Microsoft Word) when the application is launched.

{4}

theType:=Get1Resource(‘MSWD’,0);
If theType<>Nil then { the application exists }

Since some users can and do rename their applications, one can not just check for application names. Creator types should be unique (if they are registered with Apple) and no problems should be encountered this way.

Good luck with your INITs.

 
AAPL
$107.62
Apple Inc.
+0.64
MSFT
$46.73
Microsoft Corpora
+0.68
GOOG
$557.33
Google Inc.
+7.02

MacTech Search:
Community Search:

Software Updates via MacUpdate

Vitamin-R 2.20b1 - Personal productivity...
Vitamin-R creates the optimal conditions for your brain to work at its best by structuring your work into short bursts of distraction-free, highly focused activity alternating with opportunities for... Read more
Dropbox 2.10.44 - Cloud synchronization...
Dropbox is an application that creates a special Finder folder that automatically syncs online and between your computers. It allows you to both backup files and keep them up-to-date between systems... Read more
Sandvox 2.9.2 - Easily build eye-catchin...
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
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

Latest Forum Discussions

See All

Retry Review
Retry Review By Rob Thomas on October 31st, 2014 Our Rating: :: SOARING HIGHUniversal App - Designed for iPhone and iPad Flappy who? Let Retry wash all those bad bird-related memories away on a cool retro-flavored flight… right... | Read more »
Dementia: Book of the Dead Review
Dementia: Book of the Dead Review By Lee Hamlet on October 31st, 2014 Our Rating: :: A TOUGH READUniversal App - Designed for iPhone and iPad A witch hunter is sent after a demonic book in the spooky but short-lived Dementia: Book... | Read more »
Card Dungeon, the Semi-Board Game Roguel...
Card Dungeon, the Semi-Board Game Roguelike, Has Been Renovated Posted by Jessica Fisher on October 31st, 2014 [ permalink ] | Read more »
Logitech Protection + Power iPhone5/5S C...
Made by: Logitech Price: $99.99 Hardware/iOS Integration Rating: 3 out of 5 stars Usability Rating: 0.5 out of 5 stars Reuse Value Rating: 0.75 out of 5 stars Build Quality Rating: 0.75 out of 5 stars Overall Rating: 1.25 out of 5 stars | Read more »
This Is Not a Test Goes Free, Permanentl...
This Is Not a Test Goes Free, Permanently Posted by Jessica Fisher on October 31st, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Swap Heroes Review
Swap Heroes Review By Campbell Bird on October 31st, 2014 Our Rating: :: STRATEGIC SWAPPINGUniversal App - Designed for iPhone and iPad Rotate a cast of heroes to fend of waves of monsters in this difficult, puzzle rpg.   | Read more »
Night Sky Pro™ (Reference)
Night Sky Pro™ 3.0.1 Device: iOS Universal Category: Reference Price: $2.99, Version: 3.0.1 (iTunes) Description: Night Sky Pro™Wonder No More™ Night Sky Pro™ is the ultimate stargazing experience. From the creators of the original... | Read more »
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 »

Price Scanner via MacPrices.net

Apple now offering refurbished 2014 13-inch R...
The Apple Store is now offering Apple Certified Refurbished 2014 13″ Retina MacBook Pros for up to $270 off the cost of new models. An Apple one-year warranty is included with each model, and... Read more
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

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.