Use NSTextStorageDelegate instead of method swizzling

apple/MarkdownFormatter.h

@@ -4,14 +4,16 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+const NSAttributedStringKey RCTLiveMarkdownTextAttributeName = @"RCTLiveMarkdownText";
+
 const NSAttributedStringKey RCTLiveMarkdownBlockquoteDepthAttributeName = @"RCTLiveMarkdownBlockquoteDepth";
 
 @interface MarkdownFormatter : NSObject
 
-- (nonnull NSAttributedString *)format:(nonnull NSString *)text
-             withDefaultTextAttributes:(nonnull NSDictionary<NSAttributedStringKey, id> *)defaultTextAttributes
-                    withMarkdownRanges:(nonnull NSArray<MarkdownRange *> *)markdownRanges
-                     withMarkdownStyle:(nonnull RCTMarkdownStyle *)markdownStyle;
+- (void)formatAttributedString:(nonnull NSMutableAttributedString *)attributedString
+     withDefaultTextAttributes:(nonnull NSDictionary<NSAttributedStringKey, id> *)defaultTextAttributes
+            withMarkdownRanges:(nonnull NSArray<MarkdownRange *> *)markdownRanges
+             withMarkdownStyle:(nonnull RCTMarkdownStyle *)markdownStyle;
 
 NS_ASSUME_NONNULL_END
 

apple/MarkdownFormatter.mm

@@ -3,21 +3,19 @@
 
 @implementation MarkdownFormatter
 
-- (nonnull NSAttributedString *)format:(nonnull NSString *)text
-             withDefaultTextAttributes:(nonnull NSDictionary<NSAttributedStringKey, id> *)defaultTextAttributes
-                    withMarkdownRanges:(nonnull NSArray<MarkdownRange *> *)markdownRanges
-                     withMarkdownStyle:(nonnull RCTMarkdownStyle *)markdownStyle
+- (void)formatAttributedString:(nonnull NSMutableAttributedString *)attributedString
+     withDefaultTextAttributes:(nonnull NSDictionary<NSAttributedStringKey, id> *)defaultTextAttributes
+            withMarkdownRanges:(nonnull NSArray<MarkdownRange *> *)markdownRanges
+             withMarkdownStyle:(nonnull RCTMarkdownStyle *)markdownStyle
 {
-  NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:text attributes:defaultTextAttributes];
+  NSRange fullRange = NSMakeRange(0, attributedString.length);
 
   [attributedString beginEditing];
 
-  // If the attributed string ends with underlined text, blurring the single-line input imprints the underline style across the whole string.
-  // It looks like a bug in iOS, as there is no underline style to be found in the attributed string, especially after formatting.
-  // This is a workaround that applies the NSUnderlineStyleNone to the string before iterating over ranges which resolves this problem.
-  [attributedString addAttribute:NSUnderlineStyleAttributeName
-                           value:[NSNumber numberWithInteger:NSUnderlineStyleNone]
-                           range:NSMakeRange(0, attributedString.length)];
+  [attributedString setAttributes:defaultTextAttributes range:fullRange];
+
+  // We add a custom attribute to force a different comparison mode in swizzled `_textOf` method.
+  [attributedString addAttribute:RCTLiveMarkdownTextAttributeName value:@(YES) range:fullRange];
 
   for (MarkdownRange *markdownRange in markdownRanges) {
     [self applyRangeToAttributedString:attributedString
@@ -28,15 +26,15 @@ - (nonnull NSAttributedString *)format:(nonnull NSString *)text
                  defaultTextAttributes:defaultTextAttributes];
   }
 
-  [attributedString.string enumerateSubstringsInRange:NSMakeRange(0, attributedString.length)
+  [attributedString.string enumerateSubstringsInRange:fullRange
                                               options:NSStringEnumerationByLines | NSStringEnumerationSubstringNotRequired
                                            usingBlock:^(NSString * _Nullable substring, NSRange substringRange, NSRange enclosingRange, BOOL * _Nonnull stop) {
     RCTApplyBaselineOffset(attributedString, enclosingRange);
   }];
 
-  [attributedString endEditing];
+  [attributedString fixAttributesInRange:fullRange];
 
-  return attributedString;
+  [attributedString endEditing];
 }
 
 - (void)applyRangeToAttributedString:(NSMutableAttributedString *)attributedString

apple/MarkdownTextFieldObserver.h

@@ -0,0 +1,17 @@
+#import <UIKit/UIKit.h>
+#import <React/RCTUITextField.h>
+#import <RNLiveMarkdown/RCTMarkdownUtils.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface MarkdownTextFieldObserver : NSObject
+
+- (instancetype)initWithTextField:(nonnull RCTUITextField *)textField markdownUtils:(nonnull RCTMarkdownUtils *)markdownUtils;
+
+- (void)textFieldDidChange:(UITextField *)textField;
+
+- (void)textFieldDidEndEditing:(UITextField *)textField;
+
+@end
+
+NS_ASSUME_NONNULL_END

apple/MarkdownTextFieldObserver.mm

@@ -0,0 +1,73 @@
+#import <RNLiveMarkdown/MarkdownTextFieldObserver.h>
+#import "react_native_assert.h"
+
+@implementation MarkdownTextFieldObserver {
+  RCTUITextField *_textField;
+  RCTMarkdownUtils *_markdownUtils;
+  BOOL _active;
+}
+
+- (instancetype)initWithTextField:(nonnull RCTUITextField *)textField markdownUtils:(nonnull RCTMarkdownUtils *)markdownUtils
+{
+  if ((self = [super init])) {
+    react_native_assert(textField != nil);
+    react_native_assert(markdownUtils != nil);
+
+    _textField = textField;
+    _markdownUtils = markdownUtils;
+    _active = YES;
+  }
+  return self;
+}
+
+- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context
+{
+  if (_active && ([keyPath isEqualToString:@"text"] || [keyPath isEqualToString:@"attributedText"])) {
+    [self applyMarkdownFormatting];
+  }
+}
+
+- (void)textFieldDidChange:(__unused UITextField *)textField
+{
+  [self applyMarkdownFormatting];
+}
+
+- (void)textFieldDidEndEditing:(__unused UITextField *)textField
+{
+  // In order to prevent iOS from applying underline to the whole text if text ends with a link on blur,
+  // we need to update `defaultTextAttributes` which at this point doesn't contain NSUnderline attribute yet.
+  // It seems like the setter performs deep comparision, so we differentiate the new value using a counter,
+  // otherwise this trick would work only once.
+  static NSAttributedStringKey RCTLiveMarkdownForceUpdateAttributeName = @"RCTLiveMarkdownForceUpdate";
+  static NSUInteger counter = 0;
+  NSMutableDictionary *defaultTextAttributes = [_textField.defaultTextAttributes mutableCopy];
+  defaultTextAttributes[RCTLiveMarkdownForceUpdateAttributeName] = @(counter++);
+  _textField.defaultTextAttributes = defaultTextAttributes;
+  [self applyMarkdownFormatting];
+}
+
+- (void)applyMarkdownFormatting
+{
+  react_native_assert(_textField.defaultTextAttributes != nil);
+
+  if (_textField.markedTextRange != nil) {
+    return; // skip formatting during multi-stage input to avoid breaking internal state
+  }
+
+  NSMutableAttributedString *attributedText = [_textField.attributedText mutableCopy];
+  [_markdownUtils applyMarkdownFormatting:attributedText withDefaultTextAttributes:_textField.defaultTextAttributes];
+
+  UITextRange *textRange = _textField.selectedTextRange;
+
+  _active = NO; // prevent recursion
+  _textField.attributedText = attributedText;
+  _active = YES;
+
+  // Restore cursor position
+  [_textField setSelectedTextRange:textRange notifyDelegate:NO];
+
+  // Eliminate underline blinks while typing if previous text ends with a link
+  _textField.typingAttributes = _textField.defaultTextAttributes;
+}
+
+@end

apple/MarkdownTextInputDecoratorComponentView.mm

@@ -2,15 +2,17 @@
 #import <react/renderer/components/RNLiveMarkdownSpec/Props.h>
 #import <React/RCTFabricComponentsPlugins.h>
 #import <React/RCTUITextField.h>
+#import <React/RCTUITextView.h>
+#import <React/RCTTextInputComponentView.h>
 
 #import <RNLiveMarkdown/MarkdownBackedTextInputDelegate.h>
 #import <RNLiveMarkdown/MarkdownLayoutManager.h>
+#import <RNLiveMarkdown/MarkdownTextFieldObserver.h>
+#import <RNLiveMarkdown/MarkdownTextViewObserver.h>
 #import <RNLiveMarkdown/MarkdownTextInputDecoratorComponentView.h>
 #import <RNLiveMarkdown/MarkdownTextInputDecoratorViewComponentDescriptor.h>
-#import <RNLiveMarkdown/RCTBackedTextFieldDelegateAdapter+Markdown.h>
+#import <RNLiveMarkdown/MarkdownTextStorageDelegate.h>
 #import <RNLiveMarkdown/RCTMarkdownStyle.h>
-#import <RNLiveMarkdown/RCTTextInputComponentView+Markdown.h>
-#import <RNLiveMarkdown/RCTUITextView+Markdown.h>
 
 #import <objc/runtime.h>
 
@@ -21,10 +23,11 @@ @implementation MarkdownTextInputDecoratorComponentView {
   RCTMarkdownStyle *_markdownStyle;
   NSNumber *_parserId;
   MarkdownBackedTextInputDelegate *_markdownBackedTextInputDelegate;
-  __weak RCTTextInputComponentView *_textInput;
-  __weak UIView<RCTBackedTextInputViewProtocol> *_backedTextInputView;
-  __weak RCTBackedTextFieldDelegateAdapter *_adapter;
+  MarkdownTextStorageDelegate *_markdownTextStorageDelegate;
+  MarkdownTextViewObserver *_markdownTextViewObserver;
+  MarkdownTextFieldObserver *_markdownTextFieldObserver;
   __weak RCTUITextView *_textView;
+  __weak RCTUITextField *_textField;
 }
 
 + (ComponentDescriptorProvider)componentDescriptorProvider
@@ -51,21 +54,47 @@ - (instancetype)initWithFrame:(CGRect)frame
 - (void)didAddSubview:(UIView *)subview
 {
   react_native_assert([subview isKindOfClass:[RCTTextInputComponentView class]] && "Child component of MarkdownTextInputDecoratorComponentView is not an instance of RCTTextInputComponentView.");
-  _textInput = (RCTTextInputComponentView *)subview;
-  _backedTextInputView = [_textInput valueForKey:@"_backedTextInputView"];
+  RCTTextInputComponentView *textInputComponentView = (RCTTextInputComponentView *)subview;
+  UIView<RCTBackedTextInputViewProtocol> *backedTextInputView = [textInputComponentView valueForKey:@"_backedTextInputView"];
 
   _markdownUtils = [[RCTMarkdownUtils alloc] init];
   [_markdownUtils setMarkdownStyle:_markdownStyle];
   [_markdownUtils setParserId:_parserId];
 
-  [_textInput setMarkdownUtils:_markdownUtils];
-  if ([_backedTextInputView isKindOfClass:[RCTUITextField class]]) {
-    RCTUITextField *textField = (RCTUITextField *)_backedTextInputView;
-    _adapter = [textField valueForKey:@"textInputDelegateAdapter"];
-    [_adapter setMarkdownUtils:_markdownUtils];
-  } else if ([_backedTextInputView isKindOfClass:[RCTUITextView class]]) {
-    _textView = (RCTUITextView *)_backedTextInputView;
-    [_textView setMarkdownUtils:_markdownUtils];
+  if ([backedTextInputView isKindOfClass:[RCTUITextField class]]) {
+    _textField = (RCTUITextField *)backedTextInputView;
+
+    // make sure `adjustsFontSizeToFitWidth` is disabled, otherwise formatting will be overwritten
+    react_native_assert(_textField.adjustsFontSizeToFitWidth == NO);
+
+    _markdownTextFieldObserver = [[MarkdownTextFieldObserver alloc] initWithTextField:_textField markdownUtils:_markdownUtils];
+
+    // register observers for future edits
+    [_textField addTarget:_markdownTextFieldObserver action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];
+    [_textField addTarget:_markdownTextFieldObserver action:@selector(textFieldDidEndEditing:) forControlEvents:UIControlEventEditingDidEnd];
+    [_textField addObserver:_markdownTextFieldObserver forKeyPath:@"text" options:NSKeyValueObservingOptionNew context:NULL];
+    [_textField addObserver:_markdownTextFieldObserver forKeyPath:@"attributedText" options:NSKeyValueObservingOptionNew context:NULL];
+
+    // format initial value
+    [_markdownTextFieldObserver textFieldDidChange:_textField];
+
+    // TODO: register blockquotes layout manager
+    // https://github.com/Expensify/react-native-live-markdown/issues/87
+  } else if ([backedTextInputView isKindOfClass:[RCTUITextView class]]) {
+    _textView = (RCTUITextView *)backedTextInputView;
+
+    // register delegate for future edits
+    react_native_assert(_textView.textStorage.delegate == nil);
+    _markdownTextStorageDelegate = [[MarkdownTextStorageDelegate alloc] initWithTextView:_textView markdownUtils:_markdownUtils];
+    _textView.textStorage.delegate = _markdownTextStorageDelegate;
+
+    // register observer for default text attributes
+    _markdownTextViewObserver = [[MarkdownTextViewObserver alloc] initWithTextView:_textView markdownUtils:_markdownUtils];
+    [_textView addObserver:_markdownTextViewObserver forKeyPath:@"defaultTextAttributes" options:NSKeyValueObservingOptionNew context:NULL];
+
+    // format initial value
+    [_textView.textStorage setAttributedString:_textView.attributedText];
+
     NSLayoutManager *layoutManager = _textView.layoutManager; // switching to TextKit 1 compatibility mode
 
     // Correct content height in TextKit 1 compatibility mode. (See https://github.com/Expensify/App/issues/41567)
@@ -91,19 +120,26 @@ - (void)willMoveToWindow:(UIWindow *)newWindow
   if (newWindow != nil) {
     return;
   }
-  if (_textInput != nil) {
-    [_textInput setMarkdownUtils:nil];
-  }
-  if (_adapter != nil) {
-    [_adapter setMarkdownUtils:nil];
-  }
   if (_textView != nil) {
-    _markdownBackedTextInputDelegate = nil;
-    [_textView setMarkdownUtils:nil];
     if (_textView.layoutManager != nil && [object_getClass(_textView.layoutManager) isEqual:[MarkdownLayoutManager class]]) {
       [_textView.layoutManager setValue:nil forKey:@"markdownUtils"];
       object_setClass(_textView.layoutManager, [NSLayoutManager class]);
     }
+    _markdownBackedTextInputDelegate = nil;
+    [_textView removeObserver:_markdownTextViewObserver forKeyPath:@"defaultTextAttributes" context:NULL];
+    _markdownTextViewObserver = nil;
+    _markdownTextStorageDelegate = nil;
+    _textView.textStorage.delegate = nil;
+    _textView = nil;
+  }
+
+  if (_textField != nil) {
+    [_textField removeTarget:_markdownTextFieldObserver action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];
+    [_textField removeTarget:_markdownTextFieldObserver action:@selector(textFieldDidEndEditing:) forControlEvents:UIControlEventEditingDidEnd];
+    [_textField removeObserver:_markdownTextFieldObserver forKeyPath:@"text" context:NULL];
+    [_textField removeObserver:_markdownTextFieldObserver forKeyPath:@"attributedText" context:NULL];
+    _markdownTextFieldObserver = nil;
+    _textField = nil;
   }
 }
 
@@ -130,11 +166,10 @@ - (void)updateProps:(Props::Shared const &)props oldProps:(Props::Shared const &
 - (void)applyNewStyles
 {
   if (_textView != nil) {
-    // We want to use `textStorage` for applying markdown when possible. Currently it's only available for UITextView
-    [_textView textDidChange];
-  } else {
-    // apply new styles
-    [_textInput _setAttributedString:_backedTextInputView.attributedText];
+    [_textView.textStorage setAttributedString:_textView.attributedText];
+  }
+  if (_textField != nil) {
+    [_markdownTextFieldObserver textFieldDidChange:_textField];
   }
 }
 

apple/MarkdownTextInputDecoratorShadowNode.mm

@@ -188,8 +188,8 @@
     }
 
     // apply markdown
-    auto newString = [utils parseMarkdown:nsAttributedString
-                withDefaultTextAttributes:defaultNSTextAttributes];
+    NSMutableAttributedString *newString = [nsAttributedString mutableCopy];
+    [utils applyMarkdownFormatting:newString withDefaultTextAttributes:defaultNSTextAttributes];
 
     // create a clone of the old TextInputState and update the
     // attributed string box to point to the string with markdown
@@ -200,8 +200,8 @@
              AttributedStringBox::Mode::OpaquePointer) {
 
     // apply markdown
-    auto newString = [utils parseMarkdown:nsAttributedString
-                withDefaultTextAttributes:defaultNSTextAttributes];
+    NSMutableAttributedString *newString = [nsAttributedString mutableCopy];
+    [utils applyMarkdownFormatting:newString withDefaultTextAttributes:defaultNSTextAttributes];
 
     // create a clone of the old TextInputState and update the
     // attributed string box to point to the string with markdown

apple/MarkdownTextStorageDelegate.h

@@ -0,0 +1,13 @@
+#import <UIKit/UIKit.h>
+#import <React/RCTUITextView.h>
+#import <RNLiveMarkdown/RCTMarkdownUtils.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface MarkdownTextStorageDelegate : NSObject <NSTextStorageDelegate>
+
+- (instancetype)initWithTextView:(nonnull RCTUITextView *)textView markdownUtils:(nonnull RCTMarkdownUtils *)markdownUtils;
+
+@end
+
+NS_ASSUME_NONNULL_END

apple/MarkdownTextStorageDelegate.mm

@@ -0,0 +1,27 @@
+#import <RNLiveMarkdown/MarkdownTextStorageDelegate.h>
+#import "react_native_assert.h"
+
+@implementation MarkdownTextStorageDelegate {
+  RCTUITextView *_textView;
+  RCTMarkdownUtils *_markdownUtils;
+}
+
+- (instancetype)initWithTextView:(nonnull RCTUITextView *)textView markdownUtils:(nonnull RCTMarkdownUtils *)markdownUtils
+{
+  if ((self = [super init])) {
+    react_native_assert(textView != nil);
+    react_native_assert(markdownUtils != nil);
+
+    _textView = textView;
+    _markdownUtils = markdownUtils;
+  }
+  return self;
+}
+
+- (void)textStorage:(NSTextStorage *)textStorage didProcessEditing:(NSTextStorageEditActions)editedMask range:(NSRange)editedRange changeInLength:(NSInteger)delta {
+  react_native_assert(_textView.defaultTextAttributes != nil);
+
+  [_markdownUtils applyMarkdownFormatting:textStorage withDefaultTextAttributes:_textView.defaultTextAttributes];
+}
+
+@end

apple/MarkdownTextViewObserver.h

@@ -0,0 +1,13 @@
+#import <UIKit/UIKit.h>
+#import <React/RCTUITextView.h>
+#import <RNLiveMarkdown/RCTMarkdownUtils.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface MarkdownTextViewObserver : NSObject
+
+- (instancetype)initWithTextView:(nonnull RCTUITextView *)textView markdownUtils:(nonnull RCTMarkdownUtils *)markdownUtils;
+
+@end
+
+NS_ASSUME_NONNULL_END