TweetFollow Us on Twitter

Dec 95 Tips
Volume Number:11
Issue Number:12
Column Tag:Tips & Tidbits

Tips & Tidbits

By Steve Sisak, Contributing Editor

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

TIP OF THE MONTH

Arguments To “s” In MacsBug

In MacsBug, the s [step] command will take an argument which is either a count or a condition on which to stop. This can be very useful for unwinding a twisty bit of code. For example, if you keep crashing in a particular spot, but you can’t tell how you got there or what happened just before, you can break before everything goes wrong and type


  s (pc == <badspot>)

Where badspot is where you know things are wrong. Macsbug will step through all of the instructions in between here and there. You can then examine the path taken in the scrollback or, if you turn on the log first, look at it all offline with an editor. With the newest versions of MacsBug, you can even step over mixed mode. Note that it’s possible for find weirder problems, too:


 s (a0 == 0)

will step until a0 equals 0.

 

 s (<addr>^ != <current value>)

will step until the long at <addr> changes.

You can use this trick to find a really wide variety of problems. Should you use this tip, donate my fee to the American Red Cross.

- Tim Dierks

They Said I Couldn’t
Return Errors From Constructors

I have read several times that “you can’t return an error from a constructor”. This is not entirely true. See the following code example:

class exampleClass : parentClass
{
  exampleClass( int arg1, OSErr& errOut );
    // initialization constructor
...etc....
};

exampleClass::exampleClass( int arg1, OSErr& errOut )
 : parentClass()  // parent class constructor explicitly called
 , memberData() // instance variable's explict constructor
{
//  errOut = noErr;  see note #4 below
  errOut = someSystemCall( arg1 );
}

void main ( void )
{
   OSErr  err;
   exampleClass  aVar( 12, err );
   if ( err != noErr ) 
   {....etc....
}

This example “obviously” returns error information.

However, errOut will NOT have a known value if the following occurs:

1. parentClass’s explicit constructor throws an exception.

2. memberData’s explicit constructor throws an exception.

3. someSystemCall throws an exception. This example used explicit contructor calls, but the same is true for implicit constructor calls to parent classes and member data varables.

4. if the errOut = noErr line is uncommented, then at least errOut can have a known value in the absence of other exceptions.

Of course, since main isn’t doing try/catch, then the test of err != noErr is not going to happen when an exception occurs, either.

- C. Keith Ray

Is Your App Windowshade Savvy?

Many apps change the cursor within certain areas of their windows. This may be to provide the crosshairs in a drawing window, or a hand cursor if something can be dragged in an area of your window. Unfortunately, many applications forget to check whether their window is windowshaded or not. If their window is windowshaded but still the front window, they go ahead and change the cursor anyway, leading to the effect of the cursor changing over “empty space.” Looks ugly. Here’s the fix:

if (EmptyRgn( ((WindowPeek)TheWindow)->contRgn )) 
//window shade has been used

Don’t change the cursor;

else

Go ahead and change the cursor;

In the above example, TheWindow is the windowptr to the window who’s areas we are changing the cursor for.

- Richard Unger and Eric Bourque

Shortcut to Open Header Files In CodeWarrior

Here is a feature that I’d long hoped for, and recently, by accident, found.

In Metrowerk’s IDE, typing ‘command tab’ will open the corresponding .h or .cp file. For example, if you’re working in a source file named “FileName.cp” typing ‘command tab’ will open “FileName.h”. This is an extremely useful feature that I hope Symantec will adopt.

- Norman Basha

Drop Into MacsBug at a Predictable Address

When dropping into MacsBug, I often find myself in the wrong application’s code. For example, lets say I want to force-quit the finder using “es” from MacsBug. (command-option-escape will quit and then restart the Finder). To make sure the Finder is the frontmost app, I hold the mouse down in one of the Finder’s menus and press the interrupt key, and I’m dropped in at a known location (a small loop within the menu manager). Not only that, but the current menu manager is emulated on PowerMacs, further ensuring my safety. Then a simple “es” quits the Finder.

- Damon Cokenias

Lock Your Libraries, Prevent Changes

Here’s a tip that may be obvious, but it’s useful, if somewhat simple.

If you don’t want to modify the standard libraries included in a development environment (the source to PowerPlant or TCL for example) you can use the following script to lock all the files. I use this script in MPW, but should work with ToolServer as well:

### First set the current directory to the folder containing the sources 
to lock
### note that this script does sub-folders also.
### replace "xxx" with your path, e.g., "HD:MPW:Interfaces:"
directory "Full path to the folder in which the files are:"

### Then set the lock bit to ON for all files which are of
### type 'TEXT' in the current directory and all sub-directories
### Notes:
###   remove "-r" to skip sub-directories
###   make the "L" lowercase ("l") to un-lock files
###   the -f is for full paths, -s to supress directory listings
SetFile -a L `files -r -f -s -t 'TEXT'`

Anyway, just thought I’d pass it on. It’s particularly useful while using a class browser like Object Master, where you can browse all classes and it’s easy to end up editing one of the supplied classes in PowerPlant/Think Class Library/MacApp.

- Tyler Morrison

[AppleScript also supports locking and unlocking of files. Simply modify the “locked” property of x, where x is a file alias or file name with: set the locked of file x to true

EdAsst - jtk]

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

How to win big in Slots Deluxe
Cheating while gambling is illegal and morally wrong, and in some parts of the world it leads to men with names like Vinnie "Six Knuckles" Manchenzo beating you to a pulp in a dark alley. [Read more] | Read more »
How to take over the world in Dictator 2
Running a country isn't easy - especially when you're a dictator who wants to take over the world and crush everyone in your path while you do it. [Read more] | Read more »
Tips and tricks to get a higher score in...
Tank.iois - you guessed it! - another multiplayer arena battler likeAgar.io and Slither.io. It does differentiate itself by putting you in a tiny tank though, so it's not exactly the same. To help you get that all-important high score, we've got a... | Read more »
How to unlock characters in One Tap Tenn...
As the title suggests, One Tap Tennis requires only a single tap to play its particular brand of tennis, and rewards you with a ton of unlockable characters if you perform well. Fortunately for you, we at 148Apps have got a few tips and tricks to... | Read more »
Grab it now: Game Craft’s Legend of War...
The real time strategy game is now available for you to sink your teeth into, through the App Store and Google Play. Combining elements of skill, strategy and empire building, Legend of War is a real gamers’ game. [Read more] | Read more »
Skateboard Party 3 ft. Greg Lutzka (Gam...
Skateboard Party 3 ft. Greg Lutzka 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Skateboard Party is back! This third edition of the popular sports franchise features professional skater... | Read more »
Cubious (Games)
Cubious 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: Cubious – How smart are you? How high is your IQube? Solve the impossible puzzles to find out, and help a lost little cube find his... | Read more »
Goat Simulator Waste of Space (Games)
Goat Simulator Waste of Space 1.1 Device: iOS Universal Category: Games Price: $4.99, Version: 1.1 (iTunes) Description: ** IMPORTANT - SUPPORTED DEVICESiPhone 4S, iPad 2, iPod Touch 5 or better.** | Read more »
Wildfulness - Unwind in nature and calm...
Wildfulness - Unwind in nature and calm your mind with nature sounds and illustrations 1.0 Device: iOS Universal Category: Healthcare & Fitness Price: $1.99, Version: 1.0 (iTunes) Description: Spending time in nature helps you to... | Read more »
Dr. Panda Racers (Education)
Dr. Panda Racers 1.0 Device: iOS Universal Category: Education Price: $2.99, Version: 1.0 (iTunes) Description: STEP ON THE GAS, RACE AND WIN!Fasten your seat belts and get ready to race! Speed your way to the finish line while doing... | Read more »

Price Scanner via MacPrices.net

Enterprise Workers Pick Technology Over Perks...
New Adobe study shows surprising attitudes about office jobs and where the future of work is heading. Adobe has released survey findings revealing that a surprising 70 percent of U.S. office workers... Read more
Goal Zero and OtterBox Partner to Expand iPh...
Goal Zero, specialists in portable power, have announced a partnership with OtterBox, brand smartphone case protection, to offer the Slide and Slide Plus Batteries as modules compatible with the new... Read more
15-inch Retina MacBook Pros on sale for up to...
B&H Photo has 15″ Retina MacBook Pros on sale for up to $210 off MSRP. Shipping is free, and B&H charges NY tax only: - 15″ 2.2GHz Retina MacBook Pro: $1799 $200 off MSRP - 15″ 2.5GHz Retina... Read more
Clearance 2015 13-inch MacBook Airs available...
B&H Photo has clearance 2015 13″ MacBook Airs available for $250 off original MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 1.6GHz/4GB/128GB MacBook Air (MJVE2LL/A): $799... Read more
Apple refurbished Apple TVs available for up...
Apple has Certified Refurbished 32GB and 64GB Apple TVs available for up to $30 off the cost of new models. Apple’s standard one-year warranty is included with each model, and shipping is free: -... Read more
21-inch iMacs on sale for up to $120 off MSRP
B&H Photo has 21″ iMacs on sale for up to $120 off MSRP including free shipping plus NY sales tax only: - 21″ 3.1GHz iMac 4K: $1379.99 $120 off MSRP - 21″ 2.8GHz iMac: $1189 $110 off MSRP - 21″ 1... Read more
Kanex Introduces GoPower USB-C Rechargeable B...
Kanex has announced its GoPower USB-C portable battery for the USB-C MacBook, featuring the new industry standard connector and cable used for connectivity and power. Providing users with a new... Read more
Convertible and Detachable Devices Winning Ov...
According to the latest figures published by International Data Corporation (IDC), Western European shipments of ultraslim convertibles and detachables posted positive growth (44.7%) to account for... Read more
New MacBook Pros And Will MacBook Air Be Upgr...
With my mid-2013 13-inch MacBook Air closing on its third anniversary come November, I’m in system upgrade mode. Actually the Haswell CPU equipped Air is still doing a fine job, but my good wife is... Read more
Apple’s Education discount saves up to $300 o...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free, and... Read more

Jobs Board

*Apple* Project Engineer - Smart Source Inc...
SmartSource is in need of an Apple Project Engineer for a 12 month contract opportunity in Pittsburg, PA. Role: Apple Project Engineer Location: Pittsburg, PA Read more
Automotive Sales Consultant - Apple Ford Linc...
…you. The best candidates are smart, technologically savvy and are customer focused. Apple Ford Lincoln Apple Valley is different, because: $30,000 annual salary Read more
Service Assistant - *Apple* Chevrolet *App...
Apple Automotive is one of the fastest growing dealer...and it shows. Consider making the switch to the Apple Automotive Group today! At Apple Automotive, we Read more
Editor, *Apple* News - APPLE (United States...
Job Summary The Apple News team is looking for a passionate and knowledgeable editor with experience covering entertainment/pop culture and experience running social Read more
*Apple* Nissan Service Technicians - Apple A...
Apple Automotive is one of the fastest growing dealer...and it shows. Consider making the switch to the Apple Automotive Group today! At Apple Automotive , Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.