Add undo/redo support for TextInput (#1274)

Setting `allowsUndo = YES` and having the `NSTextView` delegate return a stable `NSUndoManager` mostly makes undo/redo work, but we also needed to register an undo action whenever the input contents was changed to something unexpected by JS.

This also breaks undo coalescing in a couple key places to make the input behave naturally like other apps.

Co-authored-by: Scott Kyle <[email protected]>

Author: christophpurrer

Libraries/Text/TextInput/Multiline/RCTUITextView.m

@@ -51,6 +51,7 @@ - (instancetype)initWithFrame:(CGRect)frame
     self.insertionPointColor = [NSColor selectedControlColor];
     // Fix blurry text on non-retina displays.
     self.canDrawSubviewsIntoLayer = YES;
+    self.allowsUndo = YES;
 #endif // ]TODO(macOS GH#774)
 
     _textInputDelegateAdapter = [[RCTBackedTextViewDelegateAdapter alloc] initWithTextView:self];
@@ -185,6 +186,18 @@ - (BOOL)becomeFirstResponder
 
   return success;
 }
+
+- (BOOL)resignFirstResponder
+{
+  BOOL success = [super resignFirstResponder];
+
+  if (success) {
+    // Break undo coalescing when losing focus.
+    [self breakUndoCoalescing];
+  }
+
+  return success;
+}
 #endif // ]TODO(macOS GH#774)
 
 - (void)setDefaultTextAttributes:(NSDictionary<NSAttributedStringKey, id> *)defaultTextAttributes
@@ -247,6 +260,9 @@ - (void)setAttributedText:(NSAttributedString *)attributedText
   }
 #else // [TODO(macOS GH#774)
   if (![self.textStorage isEqualTo:attributedText.string]) {
+    // Break undo coalescing when the text is changed by JS (e.g. autocomplete).
+    [self breakUndoCoalescing];
+
     if (attributedText != nil) {
       [self.textStorage setAttributedString:attributedText];
     } else {

Libraries/Text/TextInput/RCTBackedTextInputDelegateAdapter.m

@@ -263,6 +263,7 @@ @implementation RCTBackedTextViewDelegateAdapter {
   UITextRange *_previousSelectedTextRange;
 #else // [TODO(macOS GH#774)
   NSRange _previousSelectedTextRange;
+  NSUndoManager *_undoManager;
 #endif // ]TODO(macOS GH#774)
 }
 
@@ -428,6 +429,13 @@ - (BOOL)textView:(NSTextView *)textView doCommandBySelector:(SEL)commandSelector
   return commandHandled;
 }
 
+- (NSUndoManager *)undoManagerForTextView:(NSTextView *)textView {
+  if (!_undoManager) {
+    _undoManager = [NSUndoManager new];
+  }
+  return _undoManager;
+}
+
 #endif // ]TODO(macOS GH#774)
 
 #pragma mark - Public Interface

Libraries/Text/TextInput/RCTBaseTextInputView.m

@@ -144,7 +144,7 @@ - (void)setAttributedText:(NSAttributedString *)attributedText
   BOOL textNeedsUpdate = NO;
   // Remove tag attribute to ensure correct attributed string comparison.
   NSMutableAttributedString *const backedTextInputViewTextCopy = [self.backedTextInputView.attributedText mutableCopy];
-  NSMutableAttributedString *const attributedTextCopy = [attributedText mutableCopy];
+  NSMutableAttributedString *const attributedTextCopy = [attributedText mutableCopy] ?: [NSMutableAttributedString new];
 
   [backedTextInputViewTextCopy removeAttribute:RCTTextAttributesTagAttributeName
                                          range:NSMakeRange(0, backedTextInputViewTextCopy.length)];
@@ -160,7 +160,13 @@ - (void)setAttributedText:(NSAttributedString *)attributedText
 #else // [TODO(macOS GH#774)
     NSRange selection = [self.backedTextInputView selectedTextRange];
 #endif // ]TODO(macOS GH#774)
-    NSInteger oldTextLength = self.backedTextInputView.attributedText.string.length;
+    NSAttributedString *oldAttributedText = [self.backedTextInputView.attributedText copy];
+    NSInteger oldTextLength = oldAttributedText.string.length;
+
+    [self.backedTextInputView.undoManager registerUndoWithTarget:self handler:^(RCTBaseTextInputView *strongSelf) {
+      strongSelf.attributedText = oldAttributedText;
+      [strongSelf textInputDidChange];
+    }];
 
     self.backedTextInputView.attributedText = attributedText;