The simple custom text view (Mac OS X/Cocoa)

MyTextView.h

#import <Cocoa/Cocoa.h>

@interface MyTextView : NSView {
  NSMutableAttributedString *_text;
}
@end

MyTextView.m

#import "MyTextView.h"


@implementation MyTextView

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

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

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

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

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


// ----------------------------------------------------------------
// 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 {
  [[_text mutableString] appendString: aString];
  [_text addAttribute: NSFontAttributeName
                value: [NSFont userFontOfSize: 18.0f]
                range: NSMakeRange(0, [_text length])];
  [self setNeedsDisplay: YES];
}

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

@end