mouseExited is no longer called after mouseDown in NSButton subclass

Question

In building a custom NSButton, I've run into a problem handling highlight behavior. After clicking down on the button, holding, and dragging the cursor outside the button's bounds, mouseExited: and mouseEntered: events are not delivered. I understand the reason why, because in mouseDown: calling [super mouseDown:event]; will block until the click is released.

In researching this I came across this Stack Overflow post which describes the same problem. The solution noted is to add NSTrackingEnabledDuringMouseDrag to the NSTrackingArea options, which I have done, yet I continue to see this problem. I tried the other proposed solution with handling the next events in a loop, but this resulted in odd behavior. The button text color turns black on mouse down instead of highlighting the dimmed color, and it doesn't unhighlight upon releasing the mouse, it remains black.

I am using Xcode 9.3, running on macOS 10.13.4.

Here is my NSButton subclass:

@interface BorderlessButton : NSButton {
    NSColor *_tempColor;
}

@property (strong, nonatomic) NSColor *color;

@end

@interface BorderlessButton ()

@property (nonatomic) BOOL pressed;

@end

@implementation BorderlessButton

- (id)init {
    if (self = [super init]) {
        [self setUp];
    }
    return self;
}

- (id)initWithFrame:(NSRect)frameRect {
    if (self = [super initWithFrame:frameRect]) {
        [self setUp];
    }
    return self;
}

- (id)initWithCoder:(NSCoder *)aDecoder {
    if (self = [super initWithCoder:aDecoder]) {
        [self setUp];
    }
    return self;
}

- (void)setUp {
    _color = [NSColor redColor];

    [self setTitle:self.title];
    [self setButtonType:NSButtonTypeMomentaryChange];
    [self setBordered:NO];

    NSTrackingArea *area = [[NSTrackingArea alloc] initWithRect:self.bounds
                                                        options:NSTrackingMouseEnteredAndExited | NSTrackingActiveAlways | NSTrackingEnabledDuringMouseDrag
                                                          owner:self
                                                       userInfo:nil];
    [self addTrackingArea:area];
}

- (void)setTitle:(NSString *)title {
    [super setTitle:title];

    NSMutableAttributedString *colorTitle = [[NSMutableAttributedString alloc] initWithAttributedString:[self attributedTitle]];
    [colorTitle addAttributes:@{NSFontAttributeName: self.font, NSForegroundColorAttributeName: self.color} range:NSMakeRange(0, [colorTitle length])];
    [self setAttributedTitle:colorTitle];
}

- (void)setColor:(NSColor *)color {
    _color = color;

    [self setTitle:self.title];
}

- (void)mouseDown:(NSEvent *)event {
    self.pressed = YES;
    [self highlight:YES];
    [super mouseDown:event]; // this blocks until released
    [self mouseUp:event];
}

- (void)mouseUp:(NSEvent *)event {
    self.pressed = NO;
    [self highlight:NO];
    [super mouseUp:event];
}

//FIXME: Not called after mouse press down and hold then exit
- (void)mouseExited:(NSEvent *)event {
    if (self.pressed) {
        [self highlight:NO];
    }
    [super mouseExited:event];
}

- (void)mouseEntered:(NSEvent *)event {
    if (self.pressed) {
        [self highlight:YES];
    }
    [super mouseEntered:event];
}

- (void)highlight:(BOOL)flag {
    if (flag) {
        if (self.isEnabled) {
            NSColor *dimmedColor = [self dimmedColor];
            _tempColor = _color;
            self.color = dimmedColor;
            [self setTitle:self.title];
        }
    } else {
        if (self.isEnabled) {
            self.color = _tempColor;
            [self setTitle:self.title];
        }
    }
}

- (NSColor *)dimmedColor {
    return [self.color colorWithAlphaComponent:0.5];
}

@end