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;

 MyControl := 0;  { default }

 CASE message OF
 doDrawCntl(theCntl, varCode, param);
 MyControl := doTestCntl(theCntl, param);
 doInitCntl(theCntl, varCode);
 doDispCntl(theCntl, varCode);
 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));

 ; { 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);

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

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


Community Search:
MacTech Search:

Software Updates via MacUpdate

BetterTouchTool 2.412 - Customize multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
Tor Browser Bundle 7.5.2 - Anonymize Web...
The Tor Browser Bundle is an easy-to-use portable package of Tor, Vidalia, Torbutton, and a Firefox fork preconfigured to work together out of the box. It contains a modified copy of Firefox that... Read more
Monosnap 3.4.11 - Versatile screenshot u...
Monosnap lets you capture screenshots, share files, and record video and .gifs! Features Capture Capture full screen, just part of the screen, or a selected window Make your crop area pixel... Read more
Yummy FTP Pro 2.0.3 - $29.99
Yummy FTP Pro is an advanced Mac file transfer app which provides a full-featured professional toolkit combined with blazing speeds and impeccable reliability, so whether you want to transfer a few... Read more
Smultron 10.1.3 - Easy-to-use, powerful...
Smultron 10 is an elegant and powerful text editor that is easy to use. You can use Smultron 10 to create or edit any text document. Everything from a web page, a note or a script to any single piece... Read more
Time Out 2.4 - Break reminder tool with...
Time Out helps remind you to take work breaks throughout the day. It has two kinds of breaks: a "Normal" break, typically for 10 minutes after 50 minutes of work, so you can move about and relax,... Read more
Iridient Developer 3.2.2 - 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
DesktopLyrics 2.6.13 - Displays current...
DesktopLyrics is an application that displays the lyrics of the song currently playing in "iTunes" right on your desktop. The lyrics for the song have to be set in iTunes; DesktopLyrics does nothing... Read more
BusyContacts 1.2.8 - 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
iClock 4.2.5 - Customizable menu bar clo...
iClock replaces the old Apple's default menu bar clock with more features, customization and increases your productivity. Features: Have your Apple or Google calendar instantly available from the... Read more

Latest Forum Discussions

See All

How PUBG, Fortnite, and the battle royal...
The history of the battle royale genre isn't a long one. While the nascent parts of the experience have existed ever since players first started killing one another online, it's really only in the past six years that the genre has coalesced into... | Read more »
Around the Empire: What have you missed...
Oh hi nice reader, and thanks for popping in to check out our weekly round-up of all the stuff that you might have missed across the Steel Media network. Yeah, that's right, it's a big ol' network. Obviously 148Apps is the best, but there are some... | Read more »
All the best games on sale for iPhone an...
It might not have been the greatest week for new releases on the App Store, but don't let that get you down, because there are some truly incredible games on sale for iPhone and iPad right now. Seriously, you could buy anything on this list and I... | Read more »
Everything You Need to Know About The Fo...
In just over a week, Epic Games has made a flurry of announcements. First, they revealed that Fortnite—their ultra-popular PUBG competitor—is coming to mobile. This was followed by brief sign-up period for interested beta testers before sending out... | Read more »
The best games that came out for iPhone...
It's not been the best week for games on the App Store. There are a few decent ones here and there, but nothing that's really going to make you throw down what you're doing and run to the nearest WiFi hotspot in order to download it. That's not to... | Read more »
Death Coming (Games)
Death Coming Device: iOS Universal Category: Games Price: $1.99, Version: (iTunes) Description: --- Background Story ---You Died. Pure and simple, but death was not the end. You have become an agent of Death: a... | Read more »
Hints, tips, and tricks for Empires and...
Empires and Puzzles is a slick match-stuff RPG that mixes in a bunch of city-building aspects to keep things fresh. And it's currently the Game of the Day over on the App Store. So, if you're picking it up for the first time today, we thought it'd... | Read more »
What You Need to Know About Sam Barlow’s...
Sam Barlow’s follow up to Her Story is #WarGames, an interactive video series that reimagines the 1983 film WarGames in a more present day context. It’s not exactly a game, but it’s definitely still interesting. Here are the top things you should... | Read more »
Pixel Plex Guide - How to Build Better T...
Pixel Plex is the latest city builder that has come to the App Store, and it takes a pretty different tact than the ones that came before it. Instead of being in charge of your own city by yourself, you have to work together with other players to... | Read more »
Fortnite Will Be Better Than PUBG on Mob...
Before last week, if you asked me which game I prefer between Fortnite Battle Royale and PlayerUnknown’s Battlegrounds (PUBG), I’d choose the latter just about 100% of the time. Now that we know that both games are primed to hit our mobile screens... | Read more »

Price Scanner via

MacBook Pro sale! B&H drops prices on new...
B&H Photo has dropped prices on new 2017 13″ MacBook Pros, with models now on sale for up to $200 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only. Their... Read more
13″ MacBook Airs on sale for $100-$150 off MS...
B&H Photo has 13″ MacBook Airs on sale for $100-$150 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 13″ 1.8GHz/128GB MacBook Air (MQD32LL/A): $899, $... Read more
Huge iMac sale! Apple reseller now offering 2...
B&H Photo has new 2017 21″ & 27″ iMacs on sale today for up to $300 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 27″ 3.8GHz iMac (MNED2LL/A): $... Read more
Sale! 1.4GHz Mac mini for $399, $100 off MSRP
B&H Photo has the 1.4GHz Mac mini on sale for $399 for a limited time. Their price is $100 off MSRP, and it’s the lowest price available for a mini from any Apple reseller: – 1.4GHz Mac mini (... Read more
Sale of the year continues as Apple resellers...
Adorama has new 2017 15″ MacBook Pros on sale for $250-$300 off MSRP. Shipping is free, and Adorama charges sales tax in NJ and NY only: – 15″ 2.8GHz Touch Bar MacBook Pro Space Gray (MPTR2LL/A): $... Read more
iPad sale continues! 9″ WiFi iPads for $50-$8...
Walmart has 9.7″ Apple iPads on sale for $50-$80 off MSRP for a limited time. Sale prices are for online orders only, in-store prices may vary: – 9″ 32GB iPad: $249.99 $80 off – 9″ 128GB iPad: $379 $... Read more
Apple resellers offer 27″ 3.4GHz 5K iMac for...
B&H Photo has new 2017 27″ 3.4GHz iMacs on sale for $200 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 27″ 3.4GHz iMac (MNE92LL/A): $1599.99 $200 off... Read more
Certified Refurbished 21″ & 27″ iMacs ava...
Apple has a full line of Certified Refurbished iMacs available for up to $350 off original MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are available: – 27... Read more
Sunday Sales: $200 off 13″ Touch Bar MacBook...
Amazon has new 2017 13″ 3.1GHz Touch Bar MacBook Pros on sale this weekend for $200 off MSRP, each including free shipping: – 13″ 3.1GHz/256GB Space Gray MacBook Pro (MPXV2LL/A): $1599.99 $200 off... Read more
B&H drops prices on 15″ MacBook Pros up t...
B&H Photo has dropped prices on new 2017 15″ MacBook Pros, now up to $300 off MSRP and matching Adorama’s price drop yesterday. Shipping is free, and B&H charges sales tax for NY & NJ... Read more

Jobs Board

Firmware Engineer - *Apple* Accessories - A...
# Firmware Engineer - Apple Accessories Job Number: 113452350 Santa Clara Valley, California, United States Posted: 28-Feb-2018 Weekly Hours: 40.00 **Job Summary** Read more
Automation and Performance Engineer, *Apple*...
# Automation and Performance Engineer, Apple Pay Job Number: 113557967 Santa Clara Valley, California, United States Posted: 09-Mar-2018 Weekly Hours: 40.00 **Job Read more
Hardware Systems Architect - *Apple* Watch...
# Hardware Systems Architect - Apple Watch Job Number: 113565323 Santa Clara Valley, California, United States Posted: 05-Mar-2018 Weekly Hours: 40.00 **Job Read more
Lead *Apple* Solution Consultant - Apple (U...
# Lead Apple Solution Consultant Chicago IL Job Number: 113560644 Chicago, Illinois, United States Posted: 10-Mar-2018 Weekly Hours: 40.00 **Job Summary** As a Lead Read more
Art Director, *Apple* Music + Beats1 Market...
# Art Director, Apple Music + Beats1 Marketing Design Job Number: 113258081 Culver City, California, United States Posted: 07-Mar-2018 Weekly Hours: 40.00 **Job Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.