okay, thanks Greg. Good to know that assistive devices isn't supposed to gate 
crash just any old cocoa party!
I'll look for the memory bug.

cheers,

J.


On 2010-02-19, at 10:53 AM, Greg Parker wrote:

> On Feb 19, 2010, at 10:41 AM, James Maxwell wrote:
>> I have a strange crash happening while trying load an open file window/sheet 
>> (NSOpenPanel). 
>> I've got a simple AppController class, which is set as the Application's 
>> delegate. This is all there is to the controller, at this point:
>> 
>> I actually have no idea why the NSAccessibility stuff is coming up, and the 
>> docs didn't shed much light for me. The bt is below. 
>> It loads the sheet, then lists the files in the selected directory, then 
>> crashes. It works fine if I disable access for assistive devices on the 
>> system, but is there some legit way around this? Some exception I should be 
>> handling? This is the first time I've run into any accessibility stuff.
>> 
>> #0  0x97c54a16 in -[NSException raise] ()
>> #1  0x931ac55c in NSAccessibilityAttributeValue ()
>> #2  0x933c443f in CopyAppKitUIElementAttributeValueNoCatch ()
>> #3  0x933c69d7 in CopyAttributeValue ()
>> #4  0x90461ad3 in _AXXMIGCopyAttributeValue ()
>> #5  0x9046bb96 in _XCopyAttributeValue ()
>> #6  0x9043dc39 in mshMIGPerform ()
>> #7  0x97b758db in __CFRunLoopRun ()
>> #8  0x97b73864 in CFRunLoopRunSpecific ()
>> #9  0x97b73691 in CFRunLoopRunInMode ()
>> #10 0x91a39f0c in RunCurrentEventLoopInMode ()
>> #11 0x91a39cc3 in ReceiveNextEventCommon ()
>> #12 0x91a39b48 in BlockUntilNextEventMatchingListInMode ()
>> #13 0x93160ac5 in _DPSNextEvent ()
>> #14 0x93160306 in -[NSApplication 
>> nextEventMatchingMask:untilDate:inMode:dequeue:] ()
>> #15 0x9312249f in -[NSApplication run] ()
>> #16 0x9311a535 in NSApplicationMain ()
>> #17 0x00002828 in main () at main.m:13
> 
> This sort of backtrace is what happens when the assistive device machinery 
> interrogates your process. If you don't write any accessibility code then 
> assistive devices might not work well with your program, but it's not 
> expected to crash. 
> 
> The first thing to do is to look in the console for an error message printed 
> by that exception. My guess is that you have a memory error elsewhere, and 
> the exception is "unrecognized selector" because your memory error mangled 
> the accessibility data structures. If that's the case then the Zombie 
> Instrument should help find the bug.
> 
> 
> -- 
> Greg Parker     [email protected]     Runtime Wrangler
> 
> 

James B Maxwell
Composer/Doctoral Student
School for the Contemporary Arts (SCA)
School for Interactive Arts + Technology (SIAT)
Simon Fraser University
[email protected]
[email protected]

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