Display hidden characters in NSTextView

Question

I am writing a text editor for Mac OS X. I need to display hidden characters in an NSTextView (such as spaces, tabs, and special characters). I have spent a lot of time se

Answer 1

I wrote a text editor a few years back - here's some meaningless code that should get you looking in (hopefully) the right direction (this is an NSLayoutManager subclass btw - and yes I know it's leaking like the proverbial kitchen sink):

- (void)drawGlyphsForGlyphRange:(NSRange)glyphRange atPoint:(NSPoint)containerOrigin
{
    if ([[[[MJDocumentController sharedDocumentController] currentDocument] editor] showInvisibles])
    {
        //init glyphs
        unichar crlf = 0x00B6; 
        NSString *CRLF = [[NSString alloc] initWithCharacters:&crlf length:1];
        unichar space = 0x00B7;
        NSString *SPACE = [[NSString alloc] initWithCharacters:&space length:1];
        unichar tab = 0x2192; 
        NSString *TAB = [[NSString alloc] initWithCharacters:&tab length:1];

        NSString *docContents = [[self textStorage] string];
        NSString *glyph;
        NSPoint glyphPoint;
        NSRect glyphRect;
        NSDictionary *attr = [[NSDictionary alloc] initWithObjectsAndKeys:[NSUnarchiver unarchiveObjectWithData:[[NSUserDefaults standardUserDefaults] objectForKey:@"invisiblesColor"]], NSForegroundColorAttributeName, nil];

        //loop thru current range, drawing glyphs
        int i;
        for (i = glyphRange.location; i < NSMaxRange(glyphRange); i++)
        {
            glyph = @"";

            //look for special chars
            switch ([docContents characterAtIndex:i])
            {
                //space
                case ' ':
                    glyph = SPACE;
                    break;

                //tab
                case '\t':
                    glyph = TAB;
                    break;

                //eol
                case 0x2028:
                case 0x2029:
                case '\n':
                case '\r':
                    glyph = CRLF;
                    break;

                //do nothing
                default:
                    glyph = @"";
                    break;                  
            }

            //should we draw?
            if ([glyph length])
            {
                glyphPoint = [self locationForGlyphAtIndex:i];
                glyphRect = [self lineFragmentRectForGlyphAtIndex:i effectiveRange:NULL];
                glyphPoint.x += glyphRect.origin.x;
                glyphPoint.y = glyphRect.origin.y;
                [glyph drawAtPoint:glyphPoint withAttributes:attr];
            }
        }
    }

    [super drawGlyphsForGlyphRange:glyphRange atPoint:containerOrigin];
}