TweetFollow Us on Twitter

CDEF Messages
Volume Number:5
Issue Number:8
Column Tag:TechNotes

Related Info: Control Manager

New CDEF Messages

By James Plamondon, Berkeley, CA

System 7.0 will present all Macintosh programmers with new opportunities and new challenges. One of the challenges will be making your code 32-bit clean. This can be particularly difficult if your code uses parts of the Toolbox that are not 32-bit clean. Some of the routines in the Control Manager, for example, are at best only 31-bit clean -- that’s close, but not close enough for System 7.0. This article will answer the challenge by explaining both the problem with, and the solution to, the Control Manager’s unclean habits.

The specific problem that this article addresses lies in the calcCRgns CDEF message sent to all CDEFs. The message is sent to a control’s CDEF to calculate the control’s enclosing region, or the enclosing region of its indicator (if any). In Inside Macintosh [IM v1 p330], the calcCRgns CDEF message is explained as follows: “Param is a QuickDraw region handle . If the high-order bit of param is set, the region requested is that of the control’s indicator rather than the control as a whole. The definition function should clear the high byte (not just the high bit) of the region handle before attempting to update the region.”

You can see that it’s pretty hard to be 32-bit clean when you’re supposed to go around clearing bytes in handles. The handle could contain a perfectly valid 32-bit address; clearing the high byte would change the address to something entirely different -- and accessing or changing anything via that address would be a terrible mistake. Yet, it is required by the Control Manager, so what is a programmer to do?

First, one can at least improve the situation by not clearing the whole high byte, as directed. Instead, just interrogate the high bit to see what region needs to be calculated, and then clear it -- leaving the rest of the bits alone. This makes the code 31-bit clean; that’s not good enough for System 7.0, but it’ll do for the old systems.

For System 7.0, Apple has defined two new CDEF messages: calcCntlRgn (10) and calcThumbRgn (11). Instead of sending a calcCRgns message and having the CDEF figure out whether the system wants the control region or the indicator (thumb) region, the system will figure out which it wants, and send the CDEF the appropriate (new) message. The CDEF can then treat the region handle like a region handle, instead of like a secret message that has to be decoded.

To make sure the world is a happy place, and that backward compatibility is maintained, a CDEF should always implement both the calcCRgns message and the new CDEF messages. That way, whether the CDEF finds itself in use under either System 7.0 or a pre-7.0 system (which is pretty likely for the next year or two), it will respond in the manner the system expects.

There are a couple of related issues. First, a control’s variation code used to be stored in the high byte of the control record’s contrlDefProc field. To get the variation code, the programmer would mask it out of the high byte. This is unclean, since the contrlDefProc field may contain a valid 32-bit address. A new routine, GetCVariant(), was provided a couple of years ago (IM v5 p222) to return the control’s variation code. Be sure to use it.

Also, whenever writing custom CDEFs or/and other DEFs, remember that The Management Reserves the Right to Add New Messages at Any Time. Therefore, be sure that if your DEF receives a message it doesn’t recognize, it just returns what it was given without doing anything (and without blowing up).

Lastly, if you’re going to add any custom messages to your custom DEF, set the new message numbers to constants greater than 128. This gives Apple the freedom it needs to add new messages, without tromping on your custom messages.

That’s about all the discussion this issue will bear. See the revision to Tech Note #212 for the official version of this same information. Below, I have appended the old, unclean calcCRgns implementation, the new and improved 31-bit clean calcCRgns implementation, and a shell CDEF entry-point function that shows how all these messages should be handled. Note that the ‘param’ actual argument is a valid handle to an empty region, so the content of the region indicated by param needs to be changed, not the value of param itself. You couldn’t make any change to param stick anyway, since it’s not a ‘var’ parameter (i.e., the CDEF gets a copy of param’s value, not its address). Also, I’m assuming the existence of some routines, such as MyCalcThumbRgn() and MyCalcCtlRgn(), that are different for each different CDEF, and which are therefore not given here.

I’d like to thank Andrew Shebanow, Larry Tesler, Charlie Oppenheimer, and Steve Goldberg at Apple -- way to go, guys!

(*****************************************************
MyControl: Main entry point.  Call appropriate
 message-handling routine.
*****************************************************)

FUNCTION MyControl(varCode: INTEGER;
 theCntl: ControlHandle;
 message: INTEGER;
 param: LONGINT): LONGINT;

BEGIN
 MyControl := 0;  { default }

 CASE message OF
 drawCntl:
 doDrawCntl(theCntl, varCode, param);
 testCntl:
 MyControl := doTestCntl(theCntl, param);
 initCntl:
 doInitCntl(theCntl, varCode);
 dispCntl:
 doDispCntl(theCntl, varCode);
 autoTrack:
 doAutoTrack(theCntl, varCode, param);

 calcCRgns: { support for pre-7.0 }
 doCalcCRgnsNew(theCntl, param);
 calcCntlRgn:  { new in System 7.0 }
 MyCalcCtlRgn(theCntl, RgnHandle(param));
 calcThumbRgn:{ new in System 7.0 }
 MyCalcThumbRgn(theCntl, RgnHandle(param));

 OTHERWISE
 ; { ignore all other messages }
 END;  { case }
END;  { MyControl }

(*****************************************************
doCalcCRgnsOld: Calculate the region the
 control or its indicator occupies in its
 window.  Old method: Only 24-bit clean
 -- don’t use this method anymore; use 
 doCalcCRgnsNew(), below.
*****************************************************)

PROCEDURE doCalcCRgnsOld(theCntl: ControlHandle;
 param: LONGINT);

BEGIN
 if (param < 0) then  { high bit is sign bit }
 begin
 { clear high BYTE and set thumb rgn }
 param := BitAnd(param, $0FFFFFFF);
 MyCalcThumbRgn(theCntl, RgnHandle(param));
 end
 else
 begin
 { clear high BYTE and set control rgn }
 param := BitAnd(param, $0FFFFFFF);
 MyCalcCtlRgn(theCntl,
 RgnHandle(param));
 end;
END;  { doCalcCRgnsOld }

(*****************************************************
doCalcCRgnsNew: New method: Only 31-bit
 clean, but that’s the best we can do.
*****************************************************)
PROCEDURE doCalcCRgnsNew(theCntl: ControlHandle;
 param: LONGINT);
BEGIN
 if (param < 0) then  { high bit is sign bit }
 begin 
 { clear high BIT and set thumb rgn }
 param := BitAnd(param, $7FFFFFFF);
 MyCalcThumbRgn(theCntl, RgnHandle(param));
 end
 else
 begin
  { clear high BIT and set control’s rgn }
 param := BitAnd(param, $7FFFFFFF);
 MyCalcCtlRgn(theCntl, RgnHandle(param));
 end;
END;  { doCalcCRgnsNew }

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

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
Adobe Lightroom 6.1.1 - Import, develop,...
Adobe Lightroom is available as part of Adobe Creative Cloud for as little as $9.99/month bundled with Photoshop CC as part of the photography package. Lightroom 6 is also available for purchase as a... Read more
File Juicer 4.41 - Extract images, video...
File Juicer is a drag-and-drop can opener and data archaeologist. Its specialty is to find and extract images, video, audio, or text from files which are hard to open in other ways. It finds and... Read more
A Better Finder Rename 9.52 - File, phot...
A Better Finder Rename is the most complete renaming solution available on the market today. That's why, since 1996, tens of thousands of hobbyists, professionals and businesses depend on A Better... Read more
OmniFocus 2.2.3 - GTD task manager with...
OmniFocus helps you manage your tasks the way that you want, freeing you to focus your attention on the things that matter to you most. Capturing tasks and ideas is always a keyboard shortcut away in... Read more
TinkerTool 5.4 - Expanded preference set...
TinkerTool is an application that gives you access to additional preference settings Apple has built into Mac OS X. This allows to activate hidden features in the operating system and in some of the... Read more
Tinderbox 6.3.1 - Store and organize you...
Tinderbox is a personal content management assistant. It stores your notes, ideas, and plans. It can help you organize and understand them. And Tinderbox helps you share ideas through Web journals... Read more
Parallels Desktop 10.2.2 - Run Windows a...
Parallels Desktop is simply the world's bestselling, top-rated, and most trusted solution for running Windows applications on your Mac. With Parallels Desktop for Mac, you can seamlessly run both... Read more
Adobe Premiere Pro CC 2015 9.0.1 - Digit...
Premiere Pro CC 2015 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Premiere Pro customer). Premiere Pro CS6 is still available for... Read more
Adobe After Effects CC 2015 13.5.1 - Cre...
After Effects CC 2015 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous After Effects customer). After Effects CS6 is still available... 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 »
OPERATION DRACULA (Games)
OPERATION DRACULA 1.0.1 Device: iOS Universal Category: Games Price: $5.99, Version: 1.0.1 (iTunes) Description: 25% off launch sale!!! 'Could prove to be one of the most accurate representations of the Japanese bullet hell shmup... | Read more »
Race The Sun (Games)
Race The Sun 1.01 Device: iOS iPhone Category: Games Price: $4.99, Version: 1.01 (iTunes) Description: You are a solar craft. The sun is your death timer. Hurtle towards the sunset at breakneck speed in a futile race against time.... | Read more »
Tap Delay (Music)
Tap Delay 1.0.0 Device: iOS Universal Category: Music Price: $4.99, Version: 1.0.0 (iTunes) Description: Back in the “old days”, producers and engineers created delay and echo effects using tape machines. Tap Delay combines the warm... | Read more »
This Week at 148Apps: July 20-24, 2015
July is Heating Up 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... | Read more »
Red Game Without A Great Name (Games)
Red Game Without A Great Name 1.0.3 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.3 (iTunes) Description: The mechanical bird is flying through an unfriendly, Steampunk world. Help it avoid obstacles and deadly... | Read more »
Warhammer: Arcane Magic (Games)
Warhammer: Arcane Magic 1.0.2 Device: iOS Universal Category: Games Price: $9.99, Version: 1.0.2 (iTunes) Description: Engage in epic battles and tactical gameplay that challenge both novice and veteran in Warhammer: Arcane Magic, a... | Read more »
Mazes of Karradash (Games)
Mazes of Karradash 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: The city of Karradash is under attack: the monsters of the Shadow Realms are emerging from the depths.No adventurer is... | Read more »
Battle Golf is the Newest Game from the...
Wrassling was a pretty weird - and equally great - little wressling game. Now the developers, Folmer Kelly and Colin Lane, have turned their attention to a different sport: golfing. This is gonna be weird. [Read more] | Read more »
Qbert Rebooted has the App Store Going...
The weird little orange... whatever... is back, mostly thanks to that movie which shall remain nameless (you know the one). But anyway it's been "rebooted" and now you can play the fancy-looking Qbert Rebooted on iOS devices. [Read more] | Read more »

Price Scanner via MacPrices.net

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
12-inch MacBooks in stock for $20 off, save o...
Adorama has 12″ Retina MacBooks in stock for $20 off MSRP including free shipping plus NY & NJ sales tax only. For a limited time, Adorama will include a free Apple USB-C to USB Adapter, free 4-... Read more
College Student Deals: Additional $100 off Ma...
Take an additional $100 off all MacBooks and iMacs at Best Buy Online with their College Students Deals Savings, valid through August 8, 2015. Anyone with a valid .EDU email address can take... Read more
2015 13-inch 2.7GHz Retina MacBook Pro on sal...
B&H Photo has the new 2015 13″ 2.7GHz/128GB Retina MacBook Pro on sale today for $1199 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
2.8GHz Mac mini available for $988, includes...
Adorama has the 2.8GHz Mac mini available for $988, $11 off MSRP, including a free copy of Apple’s 3-Year AppleCare Protection Plan. Shipping is free, and Adorama charges sales tax in NY & NJ... 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
High-Precision Battery Fuel Gauge IC Extends...
Renesas Electronics Corporation has announced its new lithium-ion (Li-ion) battery fuel gauge IC, the RAJ240500, designed to extend battery life for connected mobile devices such as tablets, notebook... Read more
27-inch 3.3GHz 5K iMac on sale for $1799, $20...
B&H Photo has the 27″ 3.3GHz 5K iMac on sale for $1799 including free shipping plus NY tax only. Their price is $200 off MSRP, and it’s the lowest price available for this model from any Apple... Read more
Twelve South Free Dual Screen Backgrounds Co...
Twelve South has posted a second collection of travel Desktop photos, noting: For the Twelve South team, a vacation is never just a vacation. It’s a time to try out new prototypes on the road, visit... Read more
Apple Refurbished iMacs available for up to $...
The Apple Store has Apple Certified Refurbished iMacs available for up to $380 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 27″ 3.5GHz 5K iMac – $1949 $... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales. Specialist - Retail Customer Service and Sales. Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales. Specialist - Retail Customer Service and Sales. Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Customer Experience (ACE) Leader - A...
…management to deliver on business objectives Training partner store staff on Apple products, services, and merchandising guidelines Coaching partner store staff on Read more
Project Manager - *Apple* Pay Security - Ap...
**Job Summary** The Apple Pay Security team is seeking a highly organized, results-driven Project Manager to drive the development of Apple Pay Security. If you are Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.