TweetFollow Us on Twitter

June 1994 - Graphical Truffles

Graphical Truffles

The Debugging Version of QuickDraw GX

Pete ("Luke") Alexander

By now, many of you have installed one of the beta versions of QuickDraw GX onto your Macintosh -- and possibly by the time you read this, QuickDraw GX Software Developer's Kit version 1.0 will be available from APDA. Maybe you've played with the various sample applications and are now ready to work on your first QuickDraw GX application. Perhaps you've even read my article in develop; Issue 15, "Getting Started With QuickDraw GX." In this column, I'll talk about something I referred to briefly in that article: the two versions of QuickDraw GX's combined graphics and layout portions, and how to take advantage of the debugging version during the development of your QuickDraw GX-based application. Along the way I'll update you on a few changes since I wrote the article.

THE EXTENSIONS OF QUICKDRAW GX
The QuickDraw GX system extension comes in two flavors: a nondebugging and a debugging version. When you run the QuickDraw GX installer script, the nondebugging version is installed, including the complete QuickDraw GX system. The nondebugging version is lean and mean, so it's significantly faster than the debugging version; it performs quite a bit less error checking than the debugging version.

The debugging version of the extension provides extensive error checking and other debugging amenities. When developing a QuickDraw GX application, you should use this version to shake out the bugs. The debugging extension is in the DEBUG Init folder and is named "GXGraphics (debug)" in version 1.0 (it used to be named aSecretGraphics.debug); just drag it into your System Folder and reboot. As your system starts up you'll see the debugging extension's icon displayed before the QuickDraw GX icon.

An explanation of what's really going on here may help clarify things (and it has changed): There are actually three extensions within the QuickDraw GX extension -- one for graphics and layout, one for printing, and one for the Finder printing extension. The QuickDraw GX extension knows, if "GXGraphics (debug)" has already loaded, to use that extension instead of the nondebugging version of the graphics and layout extension. (Note that since the debugging extension must load before the nondebugging version, you should not change the debugging extension's name.)

THE ADVANTAGES OF THE DEBUGGING VERSION DURING DEVELOPMENT
Let's look at some differences between the two extensions, and specifically how to take advantage of the debugging version during the development of your QuickDraw GX application.

Notices, warnings, and errors. With the debugging version of the extension, you can get three types of information about drawing problems: notices, warnings, and errors. For a complete list of these, look at the graphics errors.h interface file. The many notices, warnings, and errors defined between #ifdef debugging and #endif in that file are available only with the debugging version. You'll need to #define debugging in your application to take advantage of them. (Make sure debugging is not defined when you build your final version.)

With the nondebugging version, notices aren't available at all, and the list of errors and warnings you need to respond to in your application consists only of those relatively few that lie outside #ifdef debugging and #endif in the graphics errors.h file. Your application must be set up to handle these errors and warnings, which in general indicate that the QuickDraw GX system could not honor your application's request. For example:

shape_is_nil
size_of_path_exceeds_implementation_limit
picture_index_out_of_range

The debugging version checks for errors that you're likely to run into while developing your application, such as passing a negative pen size to GXSetShapePen or a curve to GXGetGlyphMetrics. The nondebugging version doesn't check for these types of errors; it assumes you've already shaken them out of the code.

Validation routines. The GXSetValidation and GXValidateShape routines are available only in the debugging version. These routines allow your application to tell whether it's passing valid parameters into a QuickDraw GX function, to validate the contents of all QuickDraw GX objects (such as a shape, style, and ink) before their use, and to validate the QuickDraw GX memory your application is using.

Speed optimizations. The nondebugging version has optimizations for speed built in -- not only fewer error checks but also inline functions. The debugging version doesn't optimize for speed. This shouldn't have any impact on your application development except that there's not a one-to-one correspondence between stack crawls using the debugging and nondebugging versions. A performance analysis of your QuickDraw GX application should only be donewithout the "GXGraphics (debug)" file in your Extensions folder.

GraphicsBug. The GraphicsBug debugging tool allows you to explore the contents of any QuickDraw GX object to make sure it contains the correct information. Another change from before is that GraphicsBug is available in both the debugging and nondebugging versions. This ability to spy on an object's contents is important to your application development because otherwise you could only access information in objects by making API calls, which would be very tedious during debugging.

There's a slight advantage when using GraphicsBug with the debugging version: heaps are listed by name rather than by hex address in the Heaps menu.

Memory. The debugging version's memory blocks in the QuickDraw GX heap are a bit bigger to help detect errors when your application writes over the end of a block: all the blocks end with the same signature, 'grfx'.

Special MacsBug messages. The debugging version generates MacsBug messages that are intended solely for the consumption of the Apple engineers in unusual circumstances. (One of my favorites is "Curious if this ever happens.") If we did our jobs right, you should never see one of these messages. In case you do, however, we're really interested in hearing what caused you to receive it; please let us know at AppleLink APPLE.BUGS.

CLEANING UP
You should design your application to take advantage of the extensive capabilities of the debugging extension, but turn those capabilities off when you create your final shipping application, to improve its performance. For example, calling GXValidateShape with the nondebugging extension installed will only result in a jump and return (that is, it will be a no-op). This is a wonderful method for testing the QuickDraw GX dispatcher, but it doesn't help the performance of your application.

In the final compile of your shipping application, you'll most likely want to remove all calls to validation routines, posting of notices, and extra warnings and errors available only in the debugging version. One approach would be to have various compilation flags associated with pairs of #ifdef and #endif to turn these features on and off.

For more information, see my article in Issue 15 if you haven't already -- or just dig into the QuickDraw GX documentation. Enjoy your journey into the QuickDraw GX world!

RELATED READING

  • "Getting Started With QuickDraw GX" by Pete ("Luke") Alexander, develop  Issue 15.
  • "Print Hints: Looking Ahead to QuickDraw GX" by Pete ("Luke") Alexander, develop  Issue 13.

PETE ("LUKE") ALEXANDER has been providing developer support for QuickDraw GX ever since it was way up in the air. He's happy it's making its final approach, and he's hoping it lands smack dab in the middle of your software. As a glider pilot, Luke knows how important control is -- and with QuickDraw GX, you'll be able to maneuver your software into spaces you never thought possible. Since QuickDraw GX can help you do lots of great graphics stunts that you used to have to ask him about, Luke is about to soar off into the wild blue yonder and do some stunts of his own. Soon he'll be ready for the preflight check that will launch his sabbatical faster than QuickDraw GX handles two-byte text. For many weeks he'll be thinking about nothing but white sand beaches, white puffy clouds, and white-capped mountains. He'll lie on his back and watch the sway of the trees until they stop reminding him of the swashes of L's. So if you see him somewhere in Montana, Utah, Nevada, California, or Idaho, be sure to say hello -- but try not to use any words that have a G and an X in them. *

Thanks to Hugo Ayala, Cary Clark, and Herb Derby for reviewing this column. *

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

How to get coins faster in Rodeo Stamped...
There comes a time in a cowboy or cowgirl's life when all the riding and lassoing skills in the world aren't enough. You're going to need some cold, hard cash to keep your sky zoo expanding in Rodeo Stampede. [Read more] | Read more »
Artik Games releases Splashy Cats for An...
Splashy Cats had us hooked from the title alone, and when we found out the game was literally just zig-zagging one of our favourite pop-culture references, guised as a playable cat character, down a river – our appetites were whetted to say the... | Read more »
Battle Cars (Games)
Battle Cars 1.1 Device: iOS Universal Category: Games Price: $1.99, Version: 1.1 (iTunes) Description: Welcome to the world of Battle Cars. Battle Cars is a classic arcade top-down racing game with fast mini cars and funny weapons to... | Read more »
How to get started with live.ly
One could be forgiven for thinking that there are already plenty of streaming video apps out there. It's just that the App Store charts would insist that you're mistaken. [Read more] | Read more »
Rodeo Stampede: Guide to all Savannah an...
A "gotta catch 'em all" joke seems appropriate here, even though we're talking animals in Rodeo Stampede and not pocket monsters. By now you've probably had plenty of rides, tamed some animals and built yourself a pretty nice zoo | Read more »
Is there cross-platform play in slither....
So you've sunken plenty of hours into crawling around in slither.io on your iPhone or iPad. You've got your stories of tragedy and triumph, the times you coiled four snakes at one time balanced out by the others when you had a length of more than... | Read more »
Rodeo Stampede guide to running a better...
In Rodeo Stampede, honing your skills so you can jump from animal to animal and outrun the herd as long as possible is only half the fun. Once you've tamed a few animals, you can bring them home with you. [Read more] | Read more »
VoxSyn (Music)
VoxSyn 1.0 Device: iOS Universal Category: Music Price: $6.99, Version: 1.0 (iTunes) Description: VoxSyn turns your voice into the most flexible vocal sound generator ever. Instantly following even subtle modulations of pitch and... | Read more »
Catch Battleplans on Google Play from Ju...
Real-time strategy title Battleplans is due for release on Google Play on June 30th, following its release for iOS systems last month. With its simple interface and pretty graphics, the crowd-pleaser brings a formerly overlooked genre out for the... | Read more »
iDoyle: The interactive Adventures of Sh...
iDoyle: The interactive Adventures of Sherlock Holmes - A Scandal in Bohemia 1.0 Device: iOS Universal Category: Books Price: $1.99, Version: 1.0 (iTunes) Description: Special Release Price $1.99 (Normally $3.99) | Read more »

Price Scanner via MacPrices.net

MacBook Airs on sale for up to $50-$100 off M...
B&H Photo has 13″ and 11″ MacBook Airs on sale for up to $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 1.6GHz/128GB MacBook Air: $849 $50 off list price - 11″ 1.... Read more
Brexit Vote Result Forecast To Slash UK 2016...
Uncertainty and economic volatility can be expected to increase over the next nine months, as the Brexit and concerns over the future of the EU hit IT investment, say Canalys market analysts, with... Read more
13-inch 256GB MacBook Air on sale for $1149,...
Amazon has the 2016 13″ 1.6GHz/256GB MacBook Air (model MMGG2LL/A) on sale for $1149.99 including free shipping. Their price is also $50 off MSRP. Read more
Haven App Launches New Age Of Wirless 911 Eme...
Haven from RapidSOS represents a transformation in access to emergency services from a phone call solely dependent on voice to a robust data connection for voice, text, medical/demographic data.... Read more
Cu Parachute 1.1 Retirement Success PLanning...
Tucson, Arizona based Indie developer Bradley McCarthy has announce the release of Cu (Copper) Parachute 1.1 for iPhone, iPad, and iPod touch devices — a tool with which users can continuously... Read more
Research and Markets Releases iPhone 6s Plus...
A new analysis report from Dublin-based Research and Markets observes that with the iPhone 6s Plus, Apple introduced a new rear camera module. The new device has similar structure and technology than... Read more
Apple refurbished Retina MacBook Pros availab...
Apple has Certified Refurbished 2015 13″ and 15″ Retina MacBook Pros available for up to $380 off the cost of new models. An Apple one-year warranty is included with each model, and shipping is free... Read more
Apple refurbished 11-inch MacBook Airs availa...
Apple has Certified Refurbished 11″ MacBook Airs (the latest models), available for up to $170 off the cost of new models. An Apple one-year warranty is included with each MacBook, and shipping is... Read more
Apple price trackers, updated continuously
Scan our Apple Price Trackers for the latest information on sales, bundles, and availability on systems from Apple’s authorized internet/catalog resellers. We update the trackers continuously: - 15″... Read more
12-inch 32GB and 128GB WiFi iPad Pros on sale...
B&H Photo has 12″ 32GB & 128GB WiFi iPad Pros on sale for up to $80 off MSRP, each including free shipping. B&H charges sales tax in NY only: - 12″ Space Gray 32GB WiFi iPad Pro: $749 $50... Read more

Jobs Board

*Apple* Retail - Multiple Positions, Willow...
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* iPhone 6s and New Products Tester Ne...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, Read more
*Apple* iPhone 6s and New Products Tester Ne...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, Read more
*Apple* iPhone 6s and New Products Tester Ne...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, Read more
*Apple* Retail - Multiple Positions, Towson...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.