UITextView with tappable links even when not selectable

LinkableTextView.h

//
//  LinkableTextView.h
//
//  Created by George MacKerron on 2020/01/09.
//  Copyright © 2020 George MacKerron. MIT licenced.
//

@import UIKit;

@interface LinkableTextView : UITextView

@property (nonatomic) NSDictionary* activeLinkTextAttributes;
@property (nonatomic) NSURL* activeLink;
@property (nonatomic) NSRange activeLinkRange;
@property (nonatomic) NSArray<UITextSelectionRect*>* activeLinkRects;

@end

LinkableTextView.m

//
//  LinkableTextView.m
//
//  Created by George MacKerron on 2020/01/09.
//  Copyright © 2020 George MacKerron. MIT licenced
//

#import "LinkableTextView.h"

#define MaxMovementFromLink 64.0
#define ActiveLinkOpacity 0.5

CGFloat squaredDistanceFromPointToRect(CGPoint pt, CGRect rect) {
  // explanation: https://stackoverflow.com/a/18157551/338196
  CGFloat dx = fmax(0, fmax(rect.origin.x - pt.x, pt.x - (rect.origin.x + rect.size.width)));
  CGFloat dy = fmax(0, fmax(rect.origin.y - pt.y, pt.y - (rect.origin.y + rect.size.height)));
  return dx * dx + dy * dy;
}

@implementation LinkableTextView

- (void)setActiveLink:(id)link range:(NSRange)range {
  // called with a NSString or NSURL link (and NSRange range) to activate a link
  // called with a nil link (and any old NSRange) to deactivate the active link
  
  if (! self.activeLinkTextAttributes) {  // set some default attributes if none provided
    UIColor* linkColor = self.linkTextAttributes[NSForegroundColorAttributeName];
    self.activeLinkTextAttributes = @{NSForegroundColorAttributeName:
                                        [linkColor colorWithAlphaComponent:ActiveLinkOpacity]};
  };
  
  NSMutableAttributedString* s = self.attributedText.mutableCopy;
  if (link) {
    [s removeAttribute:NSLinkAttributeName range:range];  // must remove the link, or its style takes precedence
    [s addAttributes:self.activeLinkTextAttributes range:range];
  } else {
    [s removeAttribute:NSForegroundColorAttributeName range:self.activeLinkRange];
    [s addAttribute:NSLinkAttributeName value:self.activeLink range:self.activeLinkRange];
  }
  self.attributedText = s;
  
  self.activeLink = [link isKindOfClass:NSString.class] ? [NSURL URLWithString:link] : link;
  self.activeLinkRange = range;
  
  if (self.activeLink) {
    UITextPosition* posStart = [self positionFromPosition:self.beginningOfDocument
                                                   offset:self.activeLinkRange.location];
    UITextPosition* posEnd = [self positionFromPosition:posStart offset:self.activeLinkRange.length];
    UITextRange* textRange = [self textRangeFromPosition:posStart toPosition:posEnd];
    self.activeLinkRects = [self selectionRectsForRange:textRange];
  }
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
  if (self.activeLink) [self setActiveLink:nil range:NSMakeRange(0, 0)];
  
  UITouch* touch = touches.anyObject;
  CGPoint touchPoint = [touch locationInView:self];
  UITextRange* tapRange = [self characterRangeAtPoint:touchPoint];
  NSInteger start = [self offsetFromPosition:self.beginningOfDocument toPosition:tapRange.start];
  NSInteger length = [self offsetFromPosition:tapRange.start toPosition:tapRange.end];
  NSRange targetRange = NSMakeRange(start, length);
  NSRange totalRange = NSMakeRange(0, self.attributedText.length);
  
  [self.attributedText enumerateAttribute:NSLinkAttributeName inRange:totalRange options:kNilOptions
                               usingBlock:^(id  _Nullable link, NSRange range, BOOL * _Nonnull stop) {
    if (link && NSIntersectionRange(range, targetRange).length > 0) {
      [self setActiveLink:link range:range];
      *stop = YES;
    }
  }];
  
  if (! self.activeLink) [super touchesBegan:touches withEvent:event];
}

- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
  if (! self.activeLink) {
    [super touchesMoved:touches withEvent:event];
    return;
  }
  CGPoint touchPoint = [touches.anyObject locationInView:self];
  CGFloat minSquaredDistance = DBL_MAX;
  for (UITextSelectionRect* rect in self.activeLinkRects) minSquaredDistance =
    fmin(minSquaredDistance, squaredDistanceFromPointToRect(touchPoint, rect.rect));
  if (minSquaredDistance < MaxMovementFromLink * MaxMovementFromLink) return;
  [self setActiveLink:nil range:NSMakeRange(0, 0)];
}

- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
  if (! self.activeLink) {
    [super touchesEnded:touches withEvent:event];
    return;
  }
  NSURL* link = self.activeLink;
  [self setActiveLink:nil range:NSMakeRange(0, 0)];
  [UIApplication.sharedApplication openURL:link];
}

- (void)touchesCancelled:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
  if (! self.activeLink) {
    [super touchesCancelled:touches withEvent:event];
    return;
  }
  [self setActiveLink:nil range:NSMakeRange(0, 0)];
}

@end