Open Radar

 
SUMMARY:

Setting individual row heights via [NSOutlineViewDelegate outlineView:heightOfRowByItem:] and then exposing the NSOutlineView in question to Accessibility requests results into [NSTableView preparedCellAtColumn:row:] being sent, which isn't supposed to be sent to view-based table/outline views.


STEPS TO REPRODUCE:

1) Install and run the attached ModifiedTableViewPlayground project. (This is based on Apple's TableViewPlayground sample project, with an added [NSOutlineViewDelegate outlineView:heightOfRowByItem:] implementation in ATComplexOutlineController, and a deliberate division by zero crasher in [TestOutlineView preparedCellAtColumn:row:] to highlight the problem.

2) Run Accessibility Inspector.

3) Move the mouse around over the "Complex OutlineView" window's outline view hierarchy, while watching system.log in Console.app.


EXPECTED RESULTS:

No ominous log messages.


ACTUAL RESULTS:

After hovering the mouse over a folder cell, I eventually get this message in Console:

06.08.12 01:20:59,638 TableViewPlayground[20356]: View Based NSTableView error: preparedCellAtColumn:row: was called. Please log a bug with the backtrace from this log, or stop using the method.

And the deliberate crash I added (see above) yields the following backtrace:

0   com.apple.demo.TableViewPlayground	0x0000000100fe543b -[TestOutlineView preparedCellAtColumn:row:] + 59 (ATComplexOutlineController.m:59)
1   com.apple.AppKit              	0x00007fff85082c43 -[NSTableViewCellProxy cellForProxy] + 153
2   com.apple.AppKit              	0x00007fff85082c77 -[NSTableViewCellProxy realElement] + 41
3   com.apple.AppKit              	0x00007fff84db675c -[NSAccessibilityProxy accessibilityHitTest:] + 38
4   com.apple.AppKit              	0x00007fff851d1f60 -[NSOutlineColumnMockGroup accessibilityHitTest:] + 472
5   com.apple.AppKit              	0x00007fff84fcb51d -[NSOutlineRow accessibilityHitTest:] + 301
6   com.apple.AppKit              	0x00007fff85081db1 -[NSTableView(NSTableViewAccessibility) accessibilityHitTest:] + 317
7   com.apple.AppKit              	0x00007fff8515c96a -[NSWindow(NSWindowAccessibility) accessibilityHitTest:] + 305
8   com.apple.AppKit              	0x00007fff84dcdc3d -[NSApplication(NSApplicationAccessibility) accessibilityHitTest:] + 252
9   com.apple.AppKit              	0x00007fff84db038b CopyElementAtPosition + 127
10  com.apple.HIServices          	0x00007fff8b039625 _AXXMIGCopyElementAtPosition + 143
11  com.apple.HIServices          	0x00007fff8b03fd53 _XCopyElementAtPosition + 265
12  com.apple.HIServices          	0x00007fff8b01df9e mshMIGPerform + 443
13  com.apple.CoreFoundation      	0x00007fff84136a19 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 41
14  com.apple.CoreFoundation      	0x00007fff84136759 __CFRunLoopDoSource1 + 153
15  com.apple.CoreFoundation      	0x00007fff841698bf __CFRunLoopRun + 1775
16  com.apple.CoreFoundation      	0x00007fff84168dd2 CFRunLoopRunSpecific + 290
17  com.apple.HIToolbox           	0x00007fff8c576774 RunCurrentEventLoopInMode + 209
18  com.apple.HIToolbox           	0x00007fff8c576512 ReceiveNextEventCommon + 356
19  com.apple.HIToolbox           	0x00007fff8c5763a3 BlockUntilNextEventMatchingListInMode + 62
20  com.apple.AppKit              	0x00007fff84b7cfa3 _DPSNextEvent + 685
21  com.apple.AppKit              	0x00007fff84b7c862 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 128
22  com.apple.AppKit              	0x00007fff84b73c03 -[NSApplication run] + 517
23  com.apple.AppKit              	0x00007fff84b18656 NSApplicationMain + 869
24  com.apple.demo.TableViewPlayground	0x0000000100fdcbb2 main + 34 (main.m:53)
25  libdyld.dylib                 	0x00007fff82b517e1 start + 1


REGRESSION:

-


NOTES:

Looks like NSTableView's -accessibilityHitTest: implementation fails to take the difference between being view-based or cell-based into account.


SAMPLE CODE:

http://manytricks.com/sandbox/codesamples/radar/modifiedtableviewplayground.zip