Revert "Remove deprecated TextInputClient scribble method code" (#39516)

Fixes the scribble feature (iPad handwriting input via Apple Pencil).

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

diff --git a/shell/platform/darwin/ios/framework/Source/FlutterEngine.mm b/shell/platform/darwin/ios/framework/Source/FlutterEngine.mm
index c4c434e..5113c96 100644
--- a/shell/platform/darwin/ios/framework/Source/FlutterEngine.mm
+++ b/shell/platform/darwin/ios/framework/Source/FlutterEngine.mm
@@ -986,15 +986,21 @@
 #pragma mark - FlutterViewEngineDelegate
 
 - (void)flutterTextInputView:(FlutterTextInputView*)textInputView showToolbar:(int)client {
-  [_scribbleChannel.get() invokeMethod:@"Scribble.showToolbar" arguments:@[ @(client) ]];
+  // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
+  // the framework has finished transitioning to the Scribble channel.
+  // https://github.com/flutter/flutter/pull/115296
+  [_textInputChannel.get() invokeMethod:@"TextInputClient.showToolbar" arguments:@[ @(client) ]];
 }
 
 - (void)flutterTextInputPlugin:(FlutterTextInputPlugin*)textInputPlugin
                   focusElement:(UIScribbleElementIdentifier)elementIdentifier
                        atPoint:(CGPoint)referencePoint
                         result:(FlutterResult)callback {
-  [_scribbleChannel.get()
-      invokeMethod:@"Scribble.focusElement"
+  // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
+  // the framework has finished transitioning to the Scribble channel.
+  // https://github.com/flutter/flutter/pull/115296
+  [_textInputChannel.get()
+      invokeMethod:@"TextInputClient.focusElement"
          arguments:@[ elementIdentifier, @(referencePoint.x), @(referencePoint.y) ]
             result:callback];
 }
@@ -1002,30 +1008,47 @@
 - (void)flutterTextInputPlugin:(FlutterTextInputPlugin*)textInputPlugin
          requestElementsInRect:(CGRect)rect
                         result:(FlutterResult)callback {
-  [_scribbleChannel.get()
-      invokeMethod:@"Scribble.requestElementsInRect"
+  // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
+  // the framework has finished transitioning to the Scribble channel.
+  // https://github.com/flutter/flutter/pull/115296
+  [_textInputChannel.get()
+      invokeMethod:@"TextInputClient.requestElementsInRect"
          arguments:@[ @(rect.origin.x), @(rect.origin.y), @(rect.size.width), @(rect.size.height) ]
             result:callback];
 }
 
 - (void)flutterTextInputViewScribbleInteractionBegan:(FlutterTextInputView*)textInputView {
-  [_scribbleChannel.get() invokeMethod:@"Scribble.scribbleInteractionBegan" arguments:nil];
+  // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
+  // the framework has finished transitioning to the Scribble channel.
+  // https://github.com/flutter/flutter/pull/115296
+  [_textInputChannel.get() invokeMethod:@"TextInputClient.scribbleInteractionBegan" arguments:nil];
 }
 
 - (void)flutterTextInputViewScribbleInteractionFinished:(FlutterTextInputView*)textInputView {
-  [_scribbleChannel.get() invokeMethod:@"Scribble.scribbleInteractionFinished" arguments:nil];
+  // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
+  // the framework has finished transitioning to the Scribble channel.
+  // https://github.com/flutter/flutter/pull/115296
+  [_textInputChannel.get() invokeMethod:@"TextInputClient.scribbleInteractionFinished"
+                              arguments:nil];
 }
 
 - (void)flutterTextInputView:(FlutterTextInputView*)textInputView
     insertTextPlaceholderWithSize:(CGSize)size
                        withClient:(int)client {
-  [_scribbleChannel.get() invokeMethod:@"Scribble.insertTextPlaceholder"
-                             arguments:@[ @(client), @(size.width), @(size.height) ]];
+  // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
+  // the framework has finished transitioning to the Scribble channel.
+  // https://github.com/flutter/flutter/pull/115296
+  [_textInputChannel.get() invokeMethod:@"TextInputClient.insertTextPlaceholder"
+                              arguments:@[ @(client), @(size.width), @(size.height) ]];
 }
 
 - (void)flutterTextInputView:(FlutterTextInputView*)textInputView
        removeTextPlaceholder:(int)client {
-  [_scribbleChannel.get() invokeMethod:@"Scribble.removeTextPlaceholder" arguments:@[ @(client) ]];
+  // TODO(justinmc): Switch from the TextInputClient to Scribble channel when
+  // the framework has finished transitioning to the Scribble channel.
+  // https://github.com/flutter/flutter/pull/115296
+  [_textInputChannel.get() invokeMethod:@"TextInputClient.removeTextPlaceholder"
+                              arguments:@[ @(client) ]];
 }
 
 - (void)flutterTextInputViewDidResignFirstResponder:(FlutterTextInputView*)textInputView {

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

diff --git a/shell/platform/darwin/ios/framework/Source/FlutterTextInputPlugin.mm b/shell/platform/darwin/ios/framework/Source/FlutterTextInputPlugin.mm
index 7a342c6..68b57ae 100644
--- a/shell/platform/darwin/ios/framework/Source/FlutterTextInputPlugin.mm
+++ b/shell/platform/darwin/ios/framework/Source/FlutterTextInputPlugin.mm
@@ -50,6 +50,10 @@
     @"TextInput.setEditableSizeAndTransform";
 static NSString* const kSetMarkedTextRectMethod = @"TextInput.setMarkedTextRect";
 static NSString* const kFinishAutofillContextMethod = @"TextInput.finishAutofillContext";
+// TODO(justinmc): Remove the TextInput method constant when the framework has
+// finished transitioning to using the Scribble channel.
+// https://github.com/flutter/flutter/pull/104128
+static NSString* const kDeprecatedSetSelectionRectsMethod = @"TextInput.setSelectionRects";
 static NSString* const kSetSelectionRectsMethod = @"Scribble.setSelectionRects";
 static NSString* const kStartLiveTextInputMethod = @"TextInput.startLiveTextInput";
 
@@ -2107,6 +2111,12 @@
   } else if ([method isEqualToString:kFinishAutofillContextMethod]) {
     [self triggerAutofillSave:[args boolValue]];
     result(nil);
+    // TODO(justinmc): Remove the TextInput method constant when the framework has
+    // finished transitioning to using the Scribble channel.
+    // https://github.com/flutter/flutter/pull/104128
+  } else if ([method isEqualToString:kDeprecatedSetSelectionRectsMethod]) {
+    [self setSelectionRects:args];
+    result(nil);
   } else if ([method isEqualToString:kSetSelectionRectsMethod]) {
     [self setSelectionRects:args];
     result(nil);