Cocoa custom text view with managing marked text

MyTextView.h

#import <Cocoa/Cocoa.h>


@interface MyTextView : NSView <NSTextInput, NSTextInputClient> {
  NSMutableAttributedString *_text;
  NSRange _selectedRange;
  NSRange _markedRange;
}

@end

MyTextView.m

 #import "MyTextView.h"

static const NSRange kEmptyRange = {NSNotFound, 0};

@implementation MyTextView

- (id) initWithFrame: (NSRect) frameRect {
  if (self = [super initWithFrame:frameRect]) {
    _text = [[NSMutableAttributedString alloc] init];
    _selectedRange = _markedRange = kEmptyRange;
  }
  return self;
}

- (void) dealloc {
  [_text release];
  [super dealloc];
}

- (void) updateWithDefaultTextAttributes {
  const NSRange entireRange = NSMakeRange(0, [_text length]);

  [_text removeAttribute: NSFontAttributeName
                   range: entireRange];
  [_text addAttribute: NSFontAttributeName
                value: [NSFont userFontOfSize: 18.0f]
                range: entireRange];
}

- (void) drawRect: (NSRect) theRect {
  [[NSColor whiteColor] set];
  NSFrameRect(theRect);

  NSRectFill(theRect);
  [[NSColor grayColor] set];
  NSFrameRect(theRect);

  [self updateWithDefaultTextAttributes];
  [_text drawInRect: NSMakeRect(
      theRect.origin.x + 5.0f, theRect.origin.y,
      theRect.size.width, theRect.size.height)];
}


// ----------------------------------------------------------------
// Helpers
// ----------------------------------------------------------------
- (void) removeMarkedText {
  if (_markedRange.location != NSNotFound) {
    if (NSMaxRange(_markedRange) <= [_text length])
      [_text deleteCharactersInRange: _markedRange];
    _markedRange = _selectedRange = kEmptyRange;
  }
}

- (void) appendCharacters: (id) aString {
  if ([aString isKindOfClass: [NSAttributedString class]]) {
    [_text appendAttributedString: aString];
  } else {
    [[_text mutableString] appendString: aString];
  }
}

- (void) replaceCharactersInRange: (NSRange) aRange
                         withText: (id) aString
                   effectiveRange: (NSRangePointer) effectiveRange
{
  NSRange replacementRange = aRange;

  if (replacementRange.location == NSNotFound) {
    replacementRange.location = [_text length];
    replacementRange.length = 0;
  }
  NSAssert2(
    NSMaxRange(replacementRange) <= [_text length],
    @"Out of bounds: %@ for length %u",
    NSStringFromRange(replacementRange),
    [_text length]);

  if ([aString isKindOfClass: [NSAttributedString class]]) {
    [_text replaceCharactersInRange: replacementRange
               withAttributedString: aString];
  } else {
    [_text replaceCharactersInRange: replacementRange
                         withString: aString];
  }

  if (effectiveRange != NULL) {
    *effectiveRange = NSMakeRange(replacementRange.location, [aString length]);
  }
}

/**
 * If there is no marked text, the current selection is replaced.
 * If there is no selection, the string is inserted at the insertion point.
 *
 * @param replacementRange The range to replace, computed from
 *                         the beginning of the marked text.
 */
- (NSRange) replacementMarkedRange: (NSRange) replacementRange {
  NSRange markedRange = _markedRange;

  if (markedRange.location == NSNotFound) markedRange = _selectedRange;
  if (replacementRange.location != NSNotFound) {
    NSRange newRange = markedRange;
    newRange.location += replacementRange.location;
    newRange.length += replacementRange.length;
    if (NSMaxRange(newRange) <= NSMaxRange(markedRange)) {
      markedRange = newRange;
    }
  }

  return markedRange;
}

// ----------------------------------------------------------------
// NSResponder
// ----------------------------------------------------------------
- (BOOL) acceptsFirstResponder {
  return YES;
}

- (void) keyDown: (NSEvent *) theEvent {
  [self interpretKeyEvents: [NSArray arrayWithObject: theEvent]];
}


- (void) deleteBackward: (id) sender {
  const NSUInteger length = [_text length];

  if (length > 0) {
    [_text deleteCharactersInRange: NSMakeRange(length - 1, 1)];
    [self setNeedsDisplay: YES];
  }
}

- (void) insertNewline: (id) sender {
  [self insertText: @"\n"];
}

- (void) insertTab: (id) sender {
  [self insertText: @"\t"];
}

- (void) insertText: (id) aString {
  [self appendCharacters: aString];
  [self setNeedsDisplay: YES];
}


// ----------------------------------------------------------------
// NSTextInput
// ----------------------------------------------------------------
- (void) doCommandBySelector: (SEL) aSelector {
  [super doCommandBySelector: aSelector];
}

- (void) setMarkedText: (id) aString selectedRange: (NSRange) selRange {
  [self setMarkedText: aString
        selectedRange: selRange
     replacementRange: kEmptyRange];
}

- (void) unmarkText {
}

- (BOOL) hasMarkedText {
  return _markedRange.location != NSNotFound;
}

- (NSInteger) conversationIdentifier {
  return (NSInteger) self;
}

- (NSAttributedString *) attributedSubstringFromRange: (NSRange) theRange {
  return [self attributedSubstringForProposedRange:theRange actualRange:NULL];
}

- (NSRange) markedRange {
  return _markedRange;
}

- (NSRange) selectedRange {
  return _selectedRange;
}

- (NSRect) firstRectForCharacterRange: (NSRange) theRange {
  return [self firstRectForCharacterRange:theRange actualRange:NULL];
}

- (NSUInteger) characterIndexForPoint: (NSPoint) thePoint {
  return 0;
}

- (NSArray *) validAttributesForMarkedText {
  return [NSArray array];
}


// ----------------------------------------------------------------
// NSTextInputClient (Mac OS X 10.5)
// ----------------------------------------------------------------
- (void) insertText: (id) aString
   replacementRange: (NSRange) replacementRange
{
  [self removeMarkedText];
  [self replaceCharactersInRange: replacementRange
                        withText: aString
                  effectiveRange: NULL];
  [self setNeedsDisplay: YES];
}

- (void) setMarkedText: (id) aString
         selectedRange: (NSRange) selectedRange
      replacementRange: (NSRange) replacementRange
{
  NSRange effectiveRange;

  [self replaceCharactersInRange: [self replacementMarkedRange: replacementRange]
                        withText: aString
                  effectiveRange: &effectiveRange];
  if (selectedRange.location != NSNotFound) selectedRange.location += effectiveRange.location;
  _selectedRange = selectedRange;
  _markedRange = effectiveRange;
  if ([aString length] == 0) [self removeMarkedText];
  [self setNeedsDisplay: YES];
}

- (NSAttributedString *) attributedSubstringForProposedRange: (NSRange) aRange
                                                 actualRange: (NSRangePointer) actualRange
{
  return [[[NSAttributedString alloc] init] autorelease];
}

- (NSRect) firstRectForCharacterRange: (NSRange) aRange
                          actualRange: (NSRangePointer) actualRange
{
  return NSZeroRect;
}

- (NSAttributedString *) attributedString {
  return _text;
}

@end