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.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

MacFamilyTree 7.3.4 - Create and explore...
MacFamilyTree gives genealogy a facelift: it's modern, interactive, incredibly fast, and easy to use. We're convinced that generations of chroniclers would have loved to trade in their genealogy... Read more
Yummy FTP 1.10.2 - FTP/SFTP/FTPS client...
Yummy FTP is an FTP + SFTP + FTPS file transfer client which focuses on speed, reliability and productivity. Whether you need to transfer a few files or a few thousand, schedule automatic backups, or... Read more
VueScan 9.5.08 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Iridient Developer 3.0.1 - Powerful imag...
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
Air Video Server HD 2.1.0 - Stream video...
Air Video Server HD streams videos instantly from your computer on your iPhone, iPad, iPod touch or Apple TV. No need to worry about converting or transferring files. We took everything that was... Read more
Duplicate Annihilator 5.7.5 - Find and d...
Duplicate Annihilator takes on the time-consuming task of comparing the images in your iPhoto library using effective algorithms to make sure that no duplicate escapes. Duplicate Annihilator... Read more
BusyContacts 1.0.2 - Fast, efficient con...
BusyContacts is a contact manager for OS X that makes creating, finding, and managing contacts faster and more efficient. It brings to contact management the same power, flexibility, and sharing... Read more
Capture One Pro 8.2.0.82 - RAW workflow...
Capture One Pro 8 is a professional RAW converter offering you ultimate image quality with accurate colors and incredible detail from more than 300 high-end cameras -- straight out of the box. It... Read more
Backblaze 4.0.0.872 - Online backup serv...
Backblaze is an online backup service designed from the ground-up for the Mac.With unlimited storage available for $5 per month, as well as a free 15-day trial, peace of mind is within reach with... Read more
Little Snitch 3.5.2 - Alerts you about o...
Little Snitch gives you control over your private outgoing data. Track background activity As soon as your computer connects to the Internet, applications often have permission to send any... Read more

2K Announces WWE 2K, Mobile's First...
It seems like this month has been pretty big for wrestling. First Wrestlemania, then 2K has announces that they're releasing  WWE 2K for iOS. It's a simulation-based WWE game where you'll get to play with several WWE superstars such as John Cena, ... | Read more »
How the Apple Watch Could Change the Fac...
The Apple Watch is still a ways out, but my previous musings on the wearable’s various features got me thinking: what might it be like a year after launch? Two years? Five years? What if it becomes a symbiotic part of the iOS framework to the point... | Read more »
Pie In The Sky: A Pizza Odyssey (Games)
Pie In The Sky: A Pizza Odyssey 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: A game about delivering pizza. In space. | Read more »
Chosen Gives Hopeful Singers, Songwriter...
If YouTube videos and reality TV shows like The Voice have taught us one thing, it’s that there are a lot of people out there who are anxious to show the world their talents. And if they’ve taught us a second thing, it’s that there’s an almost... | Read more »
Android's Popular OfficeSuite Now A...
Once only available for Android devices, OfficeSuite has finally landed on the app store. The Mobile Systems app lets you view, edit, create, and share Word, Excel, and PowerPoint documents as well as convert them to/from PDFs. It's touted as being... | Read more »
Warhammer: Arcane Magic is Coming Soon,...
Turbo Tape Games has announced that they're joining forces with Games Workshop to bring the turn-based strategy board game, Warhammer: Arcane Magic, to life on the iOS. | Read more »
Fast & Furious: Legacy's Creati...
| Read more »
N-Fusion and 505's Ember is Totally...
| Read more »
These are All the Apple Watch Apps and G...
The Apple Watch is less than a month from hitting store shelves, and once you get your hands on it you're probably going to want some apps and games to install. Fear not! We've compiled a list of all the Apple Watch apps and games we've been able to... | Read more »
Appy to Have Known You - Lee Hamlet Look...
Being at 148Apps these past 2 years has been an awesome experience that has taught me a great deal, and working with such a great team has been a privilege. Thank you to Rob Rich, and to both Rob LeFebvre and Jeff Scott before him, for helping me... | Read more »

Price Scanner via MacPrices.net

Adobe Brings Powerful Layout-Design Capabilit...
Adobe today announced the availability of Adobe Comp CC, a free iPad app that enables rapid creation of layout concepts for mobile, Web and print projects. With Comp CC, designers can rough out and... Read more
Apple offering refurbished 27-inch 5K iMacs f...
The Apple Store is offering Apple Certified Refurbished 27″ 3.5GHz 5K iMacs for $2119 including free shipping. Their price is $380 off the price of new models, and it’s the lowest price available for... Read more
16GB iPad mini on sale for $199, save $50
Walmart has 16GB iPad minis (1st generation) available for $199.99 on their online store, including free shipping. Their price is $50 off MSRP. Online orders only. Read more
New 128GB MacBook Airs on sale for $50 off MS...
 B&H Photo has 128GB 11″ and 13″ 2015 MacBook Airs on sale today for $50 off MSRP including free shipping plus NY sales tax only: - 11″ 1.6GHz/128GB MacBook Air (Model #MJVM2LL/A): $849 $50 off... Read more
13-inch 2.6GHz Retina MacBook Pro (refurbishe...
The Apple Store has Apple Certified Refurbished 13″ 2.6GHz/128GB Retina MacBook Pros available for $979 including free shipping. Original MSRP for this model was $1299. Read more
Save up to $600 with Apple refurbished Mac Pr...
The Apple Store is offering Apple Certified Refurbished Mac Pros for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The... Read more
Samsung Galaxy S 6 and Galaxy S 6 edge U.S. P...
Samsung Electronics America, Inc. has announced the Galaxy S 6 and Galaxy S 6 edge will be available in the U.S. beginning April 10, with pre-orders being accepted now. “We have completely reimagined... Read more
13-inch 2.5GHz MacBook Pro (refurbished) avai...
The Apple Store has Apple Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.... Read more
Save up to $80 on iPad Air 2s, NY tax only, f...
 B&H Photo has iPad Air 2s on sale for $80 off MSRP including free shipping plus NY sales tax only: - 16GB iPad Air 2 WiFi: $469.99 $30 off - 64GB iPad Air 2 WiFi: $549.99 $50 off - 128GB iPad... Read more
iMacs on sale for up to $205 off MSRP
B&H Photo has 21″ and 27″ iMacs on sale for up to $205 off MSRP including free shipping plus NY sales tax only: - 21″ 1.4GHz iMac: $1019 $80 off - 21″ 2.7GHz iMac: $1189 $110 off - 21″ 2.9GHz... Read more

Jobs Board

DevOps Software Engineer - *Apple* Pay, iOS...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
*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
Sr. Technical Services Consultant, *Apple*...
**Job Summary** Apple Professional Services (APS) has an opening for a senior technical position that contributes to Apple 's efforts for strategic and transactional Read more
Lead *Apple* Solutions Consultant - Retail...
**Job Summary** Job Summary The Lead ASC is an Apple employee who serves as the Apple business manager and influencer in a hyper-business critical Reseller's store Read more
*Apple* Pay - Site Reliability Engineer - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.