NSLineBreakByTruncatingTail scrolls text when set as a paragraph style in NSTextView

问题

I have a NSTextView, which is supposed to be fixed size. When the text comes to the bottom line and to the right edge of the designated frame I need to set the NSLineBreakByTruncatingTail in order to present user with elliptic signs and disable further typing. When I do this through setting a paragraph style on textStorage of NSTextView the text scrolls up and I see only the last line with elliptic signs in the end. My question is how to prevent NSTextView from scrolling when changing its lineBreakMode?

Thanks, Nava

EDIT: (added screenshots) Before:

After:

Now here's the code that does it:

- (void)textDidChange:(NSNotification *)notification
{
    NSString *text = [textView string];

    CGFloat width, height;
    NSRect  newFrame = self.frame;

    width = round([text widthForHeight:newFrame.size.height font:textView.font]);

    height = round([text heightForWidth:newFrame.size.width font:textView.font]);
    if (height > newFrame.size.height && width > newFrame.size.width) {
        NSTextContainer *textContainer = textView.textContainer;
        [textContainer setWidthTracksTextView:NO];
        [textContainer setHeightTracksTextView:NO];
        [textView setHorizontallyResizable:NO];
        [textView setVerticallyResizable:NO];
        [textView setAutoresizingMask:NSViewNotSizable];
        [textView setLineBreakMode:NSLineBreakByTruncatingTail];
    } 
}

Functions widthForHeight and heightForWidth are some 3rd party additions, which work well. The problem is in this sudden scroll that happens when I set NSLineBreakByTruncatingTail. Here's the function, that sets the line break mode (also 3rd party addition - from a nice developer (don't remember his name)):

- (void)setLineBreakMode:(NSLineBreakMode)lineBreakMode {
    NSDictionary* curAttributes = [[self textStorage] attributesAtIndex:0
                                                              effectiveRange:NULL];

    NSParagraphStyle *currentStyle = [curAttributes objectForKey:NSParagraphStyleAttributeName];

    if (currentStyle.lineBreakMode != lineBreakMode) {

        NSMutableParagraphStyle* paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy] ;
        [paragraphStyle setLineBreakMode:lineBreakMode] ;       
        NSMutableDictionary* attributes = [[[self textStorage] attributesAtIndex:0
                                                                  effectiveRange:NULL] mutableCopy] ;

        [attributes setObject:paragraphStyle
                       forKey:NSParagraphStyleAttributeName] ;
        [paragraphStyle release] ;
        NSAttributedString* attributedString = [[NSAttributedString alloc] initWithString:[self string]
                                                                               attributes:attributes] ;
        [attributes release] ;
        [[self textStorage] setAttributedString:attributedString] ;
        [attributedString release] ;

    }
}

来源：https://stackoverflow.com/questions/8921858/nslinebreakbytruncatingtail-scrolls-text-when-set-as-a-paragraph-style-in-nstext