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

WhiteCap 6.7.1 - Visual plug-in for iTun...
WhiteCap is a sleek and sophisticated music visualizer and screensaver that features futuristic, wireframe mesh visuals with dynamic backgrounds and colors. WhiteCap contains thousands of visual... Read more
DiskMaker X 6.0 rc5 - Make a bootable OS...
DiskMaker X (was Lion DiskMaker) helps you to build a bootable drive from the official OS X installer app (the one you download from the Mac App Store). It detects the OS X Install program with... Read more
Lyn 1.9 - Lightweight image browser and...
Lyn is a fast, lightweight image browser and viewer designed for photographers, graphic artists, and Web designers. Featuring an extremely versatile and aesthetically pleasing interface, it delivers... Read more
MacFamilyTree 8.2.1 - Create and explore...
MacFamilyTree gives genealogy a facelift: modern, interactive, convenient and fast. Explore your family tree and your family history in a way generations of chroniclers before you would have loved.... Read more
LaunchBar 6.9 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
LaunchBar 6.9 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
MacFamilyTree 8.2.1 - Create and explore...
MacFamilyTree gives genealogy a facelift: modern, interactive, convenient and fast. Explore your family tree and your family history in a way generations of chroniclers before you would have loved.... Read more
Spotify 1.0.57.474. - Stream music, crea...
Spotify is a streaming music service that gives you on-demand access to millions of songs. Whether you like driving rock, silky R&B, or grandiose classical music, Spotify's massive catalogue puts... Read more
VOX 2.8.26 - Music player that supports...
VOX just sounds better! The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all audio formats you should ever need.... Read more
beaTunes 5.0.1 - Organize your music col...
beaTunes is a full-featured music player and organizational tool for music collections. How well organized is your music library? Are your artists always spelled the same way? Any R.E.M. vs REM?... Read more

Latest Forum Discussions

See All

This War of Mine gets a new ending and m...
This War of Mine just got a big new update, featuring free DLC that adds a new ending to the game, among other exciting changes. The update is celebrating the game's two-year release anniversary. Apart from the new ending, which will be quite... | Read more »
Summon eight new heroes in Fire Emblem H...
Nintendo keeps coming at us with Fire Emblem Heroes updates, and it doesn't look like that trend is stopping anytime soon. The folks behind the game have just announced the new War of the Clerics Voting Gauntlet, expected to start next Tuesday. [... | Read more »
The best deals on the App Store this wee...
iOS publishers are pulling out all the stops this week -- there's a huge number of seriously great games at discounted prices this week. Let's not waste any time and get right down to business. [Read more] | Read more »
The House of da Vinci (Games)
The House of da Vinci 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: Enter The House of Da Vinci, a new must-try 3D puzzle adventure game. Solve mechanical puzzles, discover hidden... | Read more »
Solve the disappearance of history’s gre...
Blue Brain Games invites you to indulge in an immersive hands-on 3D puzzle adventure in similar vein to The Room series, with its debut release The House of Da Vinci. Set during the historic period of the Italian Renaissance (when Leonardo himself... | Read more »
Age of Rivals (Games)
Age of Rivals 3.3 Device: iOS Universal Category: Games Price: $.99, Version: 3.3 (iTunes) Description: Deep civilization-building strategy in a fast-paced card game! | Read more »
Panthera Frontier (Games)
Panthera Frontier 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: | Read more »
Angry Birds Evolution beginner's gu...
Angry Birds changes things up a fair bit in its latest iteration, Angry Birds Evolution. The familiar sling-shot physics mechanics are still there, but the game now features team-based gameplay, RPG elements, and a new top-down view. With all of... | Read more »
Sega Forever is for the retro game fans
Sega is launching a new retro games service titled Sega Forever, in a move that's sure to delight games enthusiasts with a bit of nostalgia. Sega's releasing five classic games for free. The titles include Sonic the Hedgehog, Phantasy Star II,... | Read more »
The Little Acre (Games)
The Little Acre 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »

Price Scanner via MacPrices.net

ABBYY TextGrabber 6 for iOS Implements Instan...
ABBYY has announced the release of TextGrabber 6.0.0, an important feature update to the company’s productivity app developed for iOS and Android devices. TextGrabber 6.0 now offers Real-Time... Read more
vPhone, First Smartphone That Can’t Be Lost,...
Austin, Texas based Hypori has introduced the vPhone, a virtual smartphone that affords every business user the benefits of separate work and personal phones, conveniently delivered on a single... Read more
Save this weekend with 2016 refurbished MacBo...
Apple has dropped prices on Certified Refurbished 2016 15″ and 13″ MacBook Pros by as much as $590 off original MSRP. An Apple one-year warranty is included with each model, and shipping is free: -... Read more
New 27-inch 3.4GHz iMac on sale for $1699, sa...
MacMall has the new 2017 27″ 3.4GHz iMac (MNE92LL/A) in stock and on sale for $1699 including free shipping. Their price is $100 off MSRP. Read more
Clearance 2016 MacBook Pros available for up...
B&H Photo has clearance 2016 13″ and 15″ MacBook Pros in stock today and on sale for up to $400 off original MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: - 15″ 2.7GHz... Read more
Apple Ranks 9th In comScore Top 50 U.S. Digit...
comScore, Inc. has released its monthly ranking of U.S. online activity at the top digital media properties for May 2017 based on data from comScore Media Metrix Multi-Platform. * Entity has... Read more
10.5-inch iPad Pros available for up to $20 o...
B&H Photo has the new 2017 10.5″ iPad Pros available for up to $20 off MSRP including free shipping plus NY & NJ sales tax only: - 64GB iPad Pro WiFi: $649 - 256GB iPad Pro WiFi: $749 - 512GB... Read more
Three Off-The-Beaten-Track iOS Apps That Dese...
One of the great things about using iPads and iPhones is the vast selection of apps available for most anything you want or need to do. The three outlined in this article have been in my core app... Read more
Apple No. 1 Spot In Gartner Top 100 Vendors i...
Gartner, Inc. has unveiled the top global 100 vendors in IT in 2016 based on their revenue across IT (excluding communication services) and component market segments. In the Gartner Global Top 100:... Read more
Clearance iMacs available for up to $300 off...
B&H Photo has clearance 21″ and 27″ Apple iMacs available starting at $949, each including free shipping plus NY & NJ sales tax only: - 27″ 3.3GHz iMac 5K: $1999 $300 off original MSRP - 27″... Read more

Jobs Board

*Apple* News Product Marketing Mgr., Publish...
…organizational consensus on strategy and vision for publisher tools, authoring, and Apple News Format.Carries this strategy and vision across the organization to Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Security Data Analyst - *Apple* Information...
…data sources need to be collected to allow Information Security to better protect Apple employees and customers from a wide range of threats.Act as the subject matter Read more
Lead *Apple* Solutions Consultant - Apple I...
…integrity, and trust.Success Metrics/Key Performance Indicators:Quantitative* Year over Year growth in Apple Product and Beyond the Box sales in the assigned Point of Read more
*Apple* Solutions Consultant till v%u00E5r...
…ethics, integrity, and trust.Success Metrics/Key Performance Indicators:QuantitativeYear over Year growth in Apple Product and Beyond the Box sales in the assigned Point Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.