[iOS] Hardware keyboard text editing shortcuts (flutter#28971)

Disallow pasting non-text into FlutterTextInputPlugin (flutter#29374)

shell/platform/darwin/ios/framework/Source/FlutterTextInputPlugin.mm

@@ -856,6 +856,42 @@ - (BOOL)canBecomeFirstResponder {
   return _textInputClient != 0;
 }
 
+- (BOOL)canPerformAction:(SEL)action withSender:(nullable id)sender {
+  if (action == @selector(paste:)) {
+    // Forbid pasting images, memojis, or other non-string content.
+    return [UIPasteboard generalPasteboard].string != nil;
+  }
+
+  return [super canPerformAction:action withSender:sender];
+}
+
+#pragma mark - UIResponderStandardEditActions Overrides
+
+- (void)cut:(id)sender {
+  [UIPasteboard generalPasteboard].string = [self textInRange:_selectedTextRange];
+  [self replaceRange:_selectedTextRange withText:@""];
+}
+
+- (void)copy:(id)sender {
+  [UIPasteboard generalPasteboard].string = [self textInRange:_selectedTextRange];
+}
+
+- (void)paste:(id)sender {
+  NSString* pasteboardString = [UIPasteboard generalPasteboard].string;
+  if (pasteboardString != nil) {
+    [self insertText:pasteboardString];
+  }
+}
+
+- (void)delete:(id)sender {
+  [self replaceRange:_selectedTextRange withText:@""];
+}
+
+- (void)selectAll:(id)sender {
+  [self setSelectedTextRange:[self textRangeFromPosition:[self beginningOfDocument]
+                                              toPosition:[self endOfDocument]]];
+}
+
 #pragma mark - UITextInput Overrides
 
 - (id<UITextInputTokenizer>)tokenizer {