react-native-navigation/lib/ios/RNNCustomTitleView.m

#import "RNNCustomTitleView.h"

@interface RNNCustomTitleView ()

@property (nonatomic, strong) RCTRootView *subView;
@property (nonatomic, strong) NSString *alignment;

@end

@implementation RNNCustomTitleView

- (instancetype)initWithFrame:(CGRect)frame subView:(RCTRootView*)subView alignment:(NSString*)alignment {
	self = [super init];
	
	if (self) {
		self.subView = subView;
		self.alignment = alignment;
		
		self.backgroundColor = [UIColor clearColor];
		self.subView.backgroundColor = [UIColor clearColor];
		
		if ([alignment isEqualToString:@"fill"]) {
			self.frame = frame;
			subView.sizeFlexibility = RCTRootViewSizeFlexibilityNone;
		} else {
			self.subView.delegate = self;
			subView.sizeFlexibility = RCTRootViewSizeFlexibilityWidthAndHeight;
		}
		
		[self addSubview:subView];
	}
	
	return self;
}

- (CGSize)sizeThatFits:(CGSize)size {
	if ([self.alignment isEqualToString:@"fill"]) {
		return size;
	}
	return [super sizeThatFits:size];
}

- (void)layoutSubviews {
	[super layoutSubviews];
	if ([self.alignment isEqualToString:@"fill"]) {
		[self.subView setFrame:self.frame];
	}
}

- (NSString *)alignment {
	return _alignment ? _alignment : @"center";
}

- (void)rootViewDidChangeIntrinsicSize:(RCTRootView *)rootView {
	if ([self.alignment isEqualToString:@"center"]) {
		[self setFrame:CGRectMake(self.frame.origin.x, self.frame.origin.y, self.subView.intrinsicContentSize.width, self.subView.intrinsicContentSize.height)];
		[self.subView setFrame:CGRectMake(0, 0, rootView.intrinsicContentSize.width, rootView.intrinsicContentSize.height)];
	}
}

@end