Adding text container to NSLayoutManager results in exception - cocoa

Question

In my cocoa application (written in Swift), I am trying to make a pagination system, where each page is an instance of CASTextView (a subclass of NSTextView). Additionally, each CASTextView retains an instance of CASTextContainer (a subclass of NSTextContainer). In order to accomplish pagination, I have made all instances of CASTextView share the same NSLayoutManager instance via a singleton pattern.
I have implemented the method - (void)layoutManager:(NSLayoutManager *)aLayoutManager didCompleteLayoutForTextContainer:(NSTextContainer *)aTextContainer atEnd:(BOOL)flag as follows:
func layoutManager(layoutManager: NSLayoutManager!,
didCompleteLayoutForTextContainer textContainer: NSTextContainer!,
atEnd layoutFinishedFlag: Bool)
{
let containers = layoutManager.textContainers
if !layoutFinishedFlag || !textContainer {
let lastContainer = containers[containers.count - 1] as NSTextContainer
if !textContainer || textContainer == lastContainer {
if layoutManager.glyphRangeForTextContainer(lastContainer).length > 0 {
addPage(nil)
}
}
}
}
Here is the code to receive the singleton instance of NSLayoutManager (CASTextView.sharedLayoutManager):
class var sharedLayoutManager: NSLayoutManager {
struct Singleton {
static let instance = NSLayoutManager()
}
return Singleton.instance // All text containers share the same layout manager.
}
The method addPage initializes a text view, replaces the text container with one of type CASTextContainer, and then replaces the layout manager with the shared layout manager, as follows:
func addPage(sender: NSNotification?) {
let midpoint = NSWidth(mainView.frame) / 2
let firstEndpoint = midpoint - 500
var rect: NSRect = NSZeroRect
let yValue: CGFloat = 50 + 1425 * CGFloat(pages.count)
mainView.frame.size = NSMakeSize(NSWidth(mainView.frame), yValue + 1675) // extend the scrolling size to account for new subview.
let origin = NSMakePoint(firstEndpoint, yValue)
let size = NSMakeSize(1000, 1375)
rect.origin = origin
rect.size = size
var nextView = CASTextView(frame: rect)
var nextContainer = CASTextContainer(containerSize: containerSize)
nextContainer.mainView = nextView
nextView.replaceTextContainer(nextContainer)
nextContainer.replaceLayoutManager(CASTextView.sharedLayoutManager)
nextView.autoresizingMask = NSAutoresizingMaskOptions.ViewNotSizable
nextView.delegate = nextView
nextView.usesFindPanel = true
mainView.addSubview(nextView)
pages.append(nextView)
for var i = 0; i < pages.count - 1; ++i {
pages[i].nextPage = pages[i + 1] // reset nextPage variable
}
}
Each CASTextView retains a reference to the next page (also of type CASTextView), and the last CASTextView is to have this reference (called nextPage) set to nil. The variable 'pages' is an array of all of the pages retained by the NSLayoutManagerDelegate (a subclass of NSViewController).
The problem: The call to addPage is executing exactly when it is intended to (when one page's text container can no longer fit all of the text), but is causing an exception to occur in the following method:
-[NSBigMutableString _getBlockStart:end:contentsEnd:forRange:stopAtLineSeparators:]: Range {0, 98} out of bounds; string length 0
I cannot find documentation on this method anywhere; the leading underscore seems to imply that it is a private method of NSString, but the stack trace shows that it is being called by -[NSString paragraphRangeForRange:] . Interestingly, the stack trace does not show that the addPage method is on the stack. Here is the stack trace:
0 CoreFoundation 0x00007fff90ef3f1c __exceptionPreprocess + 172
1 libobjc.A.dylib 0x00007fff869b274e objc_exception_throw + 43
2 CoreFoundation 0x00007fff90ef3dcd +[NSException raise:format:] + 205
3 Foundation 0x00007fff8d480b5c -[NSString _getBlockStart:end:contentsEnd:forRange:stopAtLineSeparators:] + 239
4 Foundation 0x00007fff8d4a699c -[NSString paragraphRangeForRange:] + 57
5 AppKit 0x00007fff8ea8a7fe -[NSTextView _markTextEditedForRange:] + 1405
6 AppKit 0x00007fff8ea852a0 -[NSTextView insertText:replacementRange:] + 2800
7 AppKit 0x00007fff8eaba451 -[NSTextView insertText:] + 318
8 AppKit 0x00007fff8eade292 -[NSTextView(NSKeyBindingCommands) insertNewline:] + 239
9 AppKit 0x00007fff8ea8f544 -[NSTextView doCommandBySelector:] + 195
10 AppKit 0x00007fff8f0b6a71 -[NSTextInputContext(NSInputContext_WithCompletion) doCommandBySelector:completionHandler:] + 118
11 AppKit 0x00007fff8ea64c9b -[NSKeyBindingManager(NSKeyBindingManager_MultiClients) interpretEventAsCommand:forClient:] + 1899
12 AppKit 0x00007fff8f0b54a2 __61-[NSTextInputContext _handleEvent:options:completionHandler:]_block_invoke968 + 335
13 AppKit 0x00007fff8f0b6edf -[NSTextInputContext(NSInputContext_WithCompletion) hasMarkedTextWithCompletionHandler:] + 76
14 AppKit 0x00007fff8f0b52c3 __61-[NSTextInputContext _handleEvent:options:completionHandler:]_block_invoke_3 + 95
15 AppKit 0x00007fff8f0b45d8 -[NSTextInputContext tryHandleEvent_HasMarkedText_withDispatchCondition:dispatchWork:continuation:] + 101
16 AppKit 0x00007fff8f0b5234 __61-[NSTextInputContext _handleEvent:options:completionHandler:]_block_invoke956 + 321
17 HIToolbox 0x00007fff8e0e204f __TSMProcessRawKeyEventWithOptionsAndCompletionHandler_block_invoke_5 + 70
18 AppKit 0x00007fff8f0ae056 __55-[NSTextInputContext handleTSMEvent:completionHandler:]_block_invoke174 + 2387
19 AppKit 0x00007fff8f0b6edf -[NSTextInputContext(NSInputContext_WithCompletion) hasMarkedTextWithCompletionHandler:] + 76
20 AppKit 0x00007fff8f0ad674 __55-[NSTextInputContext handleTSMEvent:completionHandler:]_block_invoke_2 + 95
21 AppKit 0x00007fff8f0ab3c8 -[NSTextInputContext tryHandleTSMEvent_HasMarkedText_withDispatchCondition:dispatchWork:continuation:] + 101
22 AppKit 0x00007fff8f0ad3d0 -[NSTextInputContext handleTSMEvent:completionHandler:] + 3293
23 AppKit 0x00007fff8ea8410e _NSTSMEventHandler + 324
24 HIToolbox 0x00007fff8decd6c8 _ZL23DispatchEventToHandlersP14EventTargetRecP14OpaqueEventRefP14HandlerCallRec + 1128
25 HIToolbox 0x00007fff8deccb8e _ZL30SendEventToEventTargetInternalP14OpaqueEventRefP20OpaqueEventTargetRefP14HandlerCallRec + 386
26 HIToolbox 0x00007fff8decca02 SendEventToEventTargetWithOptions + 43
27 HIToolbox 0x00007fff8e0db37c SendTSMEvent_WithCompletionHandler + 417
28 HIToolbox 0x00007fff8e0db87c __SendUnicodeTextAEToUnicodeDoc_WithCompletionHandler_block_invoke + 400
29 HIToolbox 0x00007fff8e0dbb36 __SendFilterTextEvent_WithCompletionHandler_block_invoke + 189
30 HIToolbox 0x00007fff8e0db3d0 SendTSMEvent_WithCompletionHandler + 501
31 HIToolbox 0x00007fff8e0db6bf SendFilterTextEvent_WithCompletionHandler + 236
32 HIToolbox 0x00007fff8e0d8a31 SendUnicodeTextAEToUnicodeDoc_WithCompletionHandler + 295
33 HIToolbox 0x00007fff8e0dd329 __utDeliverTSMEvent_WithCompletionHandler_block_invoke_2 + 296
34 HIToolbox 0x00007fff8e0dd1f8 __utDeliverTSMEvent_WithCompletionHandler_block_invoke + 437
35 HIToolbox 0x00007fff8e0d84ad TSMKeyEvent_WithCompletionHandler + 701
36 HIToolbox 0x00007fff8e0e1fd0 __TSMProcessRawKeyEventWithOptionsAndCompletionHandler_block_invoke_4 + 251
37 HIToolbox 0x00007fff8e0e1ec6 __TSMProcessRawKeyEventWithOptionsAndCompletionHandler_block_invoke_3 + 330
38 HIToolbox 0x00007fff8e0e1d02 __TSMProcessRawKeyEventWithOptionsAndCompletionHandler_block_invoke_2 + 259
39 HIToolbox 0x00007fff8e0e1b85 __TSMProcessRawKeyEventWithOptionsAndCompletionHandler_block_invoke + 251
40 HIToolbox 0x00007fff8e0e198f TSMProcessRawKeyEventWithOptionsAndCompletionHandler + 3068
41 AppKit 0x00007fff8f0b5046 __61-[NSTextInputContext _handleEvent:options:completionHandler:]_block_invoke945 + 131
42 AppKit 0x00007fff8f0b4502 -[NSTextInputContext tryTSMProcessRawKeyEvent:dispatchCondition:setupForDispatch:furtherCondition:dispatchWork:continuation:] + 127
43 AppKit 0x00007fff8f0b4b35 -[NSTextInputContext _handleEvent:options:completionHandler:] + 1266
44 AppKit 0x00007fff8ea8394e -[NSTextInputContext handleEvent:] + 109
45 AppKit 0x00007fff8ea63368 -[NSView interpretKeyEvents:] + 207
46 AppKit 0x00007fff8ea837cd -[NSTextView keyDown:] + 695
47 AppKit 0x00007fff8efa2d7b -[NSWindow _reallySendEvent:] + 1959
48 AppKit 0x00007fff8ea337bc -[NSWindow sendEvent:] + 368
49 AppKit 0x00007fff8e9e5dc0 -[NSApplication sendEvent:] + 4008
50 AppKit 0x00007fff8e871b48 -[NSApplication run] + 711
51 AppKit 0x00007fff8e85d2de NSApplicationMain + 1778
52 Application 0x000000010000e2a5 top_level_code + 37
53 Application 0x000000010000e2da main + 42
54 libdyld.dylib 0x00007fff9422d5c9 start + 1
55 ??? 0x0000000000000003 0x0 + 3
)

Answer 1

The error was occurring as a result of my call to replaceLayoutManager. I altered the way that I initialize the text view. Rather than using the init(frame: frameRect) constructor, I utilized the designated initializer by separately initializing a text container as such:
var nextContainer = CASTextContainer(containerSize: containerSize)
var nextView = CASTextView(frame: rect, textContainer: nextContainer)
I then proceeded to call mainView.addSubview(nextView), and after the subview was added, I called the following:
CASTextView.sharedLayoutManager.addTextContainer(nextContainer)
which then allowed for the pagination effect to take place.