As a learning experience, I'm trying to make a trivial document-based app: a
window with a text view that can edit and save RTF files.
What I have now almost works, except that whenever I save changes, the text
view scrolls to the top. Needless to say, this would be very annoying in a
real text-editing app. I suspect it's something trivial about document-based
apps and/or bindings that I just don't understand. Can someone explain what's
going on?
--- The setup ---
I barely wrote ten lines of code. I created a new document-based project and
added this ivar to MyDocument.h:
NSMutableAttributedString *myText;
(I see the document class in TextEdit uses an NSTextStorage. But the docs say
NSTextView can be bound to an attributed string, so I figured I should be able
to use one.)
I wrote three methods, two of which the project template had stubbed out for me:
- (NSDictionary *)myDocumentAttributes
{
return [NSDictionary dictionaryWithObject:NSRTFTextDocumentType
forKey:NSDocumentTypeDocumentAttribute];
}
- (NSData *)dataOfType:(NSString *)typeName error:(NSError **)outError
{
return [myText dataFromRange:NSMakeRange(0, [myText length])
documentAttributes:[self myDocumentAttributes]
error:outError];
}
- (BOOL)readFromData:(NSData *)data ofType:(NSString *)typeName error:(NSError
**)outError
{
[myText release];
myText = [[NSMutableAttributedString alloc] initWithData:data
options:[self
myDocumentAttributes]
documentAttributes:nil
error:outError];
return (myText != nil);
}
In IB, I put an NSTextView in the window and bound its Attributed String to the
File's Owner with "myText" as the model key path.
In the Info.plist, I specified rtf as the document type.
--- The weirdness ---
I paste a longish amount of text into the text view and hit Command-S. While
the sheet for the save panel is sliding down, I can see the text view scroll to
the top of the text. Aside from this, saving and opening files seems to work.
--- Attempt to diagnose ---
I created a subview of NSTextView and put a breakpoint in scrollPoint:. When I
hit Save, I get the stack trace below.
* The point being passed to scrollPoint: is {0, 467} which doesn't seem to
correspond to anything. The scroll view's height is 599.
* Why is the text view being sent a setTextColor: message?
#0 0x100001b72 in -[MyTextView scrollPoint:] at MyTextView.m:16
#1 0x7fff81626fb3 in -[NSLayoutManager(NSPrivate)
_resizeTextViewForTextContainer:]
#2 0x7fff81625758 in -[NSLayoutManager(NSPrivate)
_recalculateUsageForTextContainerAtIndex:]
#3 0x7fff8162c099 in -[NSLayoutManager
textStorage:edited:range:changeInLength:invalidatedRange:]
#4 0x7fff8162be59 in -[NSTextStorage
_notifyEdited:range:changeInLength:invalidatedRange:]
#5 0x7fff81686f3c in -[NSTextStorage processEditing]
#6 0x7fff816879e3 in -[NSTextStorage endEditing]
#7 0x7fff86bde763 in -[NSMutableAttributedString removeAttribute:range:]
#8 0x7fff816a2315 in -[NSTextView setTextColor:]
#9 0x7fff81b15c33 in -[_NSTextPlugin showValue:inObject:]
#10 0x7fff816d8e38 in -[NSValueBinder discardEditing]
#11 0x7fff81adefe2 in -[NSValueBinder
commitEditingWithDelegate:didCommitSelector:contextInfo:]
#12 0x7fff8184deb2 in -[NSDocument
saveDocumentWithDelegate:didSaveSelector:contextInfo:]
#13 0x7fff81677e9a in -[NSApplication sendAction:to:from:]
#14 0x7fff8169c41e in -[NSMenuItem _corePerformAction]
#15 0x7fff8169c188 in -[NSCarbonMenuImpl
performActionWithHighlightingForItemAtIndex:]
#16 0x7fff81681e09 in -[NSMenu performKeyEquivalent:]
#17 0x7fff81680bb1 in -[NSApplication _handleKeyEquivalent:]
#18 0x7fff81551645 in -[NSApplication sendEvent:]
#19 0x7fff814e84da in -[NSApplication run]
#20 0x7fff814e11a8 in NSApplicationMain
#21 0x100001b50 in main at main.m:13
--Andy
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