[framework] Add Look Up to selection controls for iOS (flutter#131798)

This PR adds framework support for the Look Up feature in iOS. 

https://github.com/flutter/flutter/assets/36148254/d301df79-4e23-454f-8742-2f8e39c2960c

The corresponding merged engine PR can be found [here](flutter/engine#43308).
This PR addresses flutter#82907 
More details are available in this [design doc.](flutter.dev/go/add-missing-features-to-selection-controls)

This is the same PR as flutter#130532, this is an attempt to fix the Google Testing issue

Author: LouiseHsu

packages/flutter/lib/src/cupertino/adaptive_text_selection_toolbar.dart

@@ -94,6 +94,7 @@ class CupertinoAdaptiveTextSelectionToolbar extends StatelessWidget {
     required VoidCallback? onCut,
     required VoidCallback? onPaste,
     required VoidCallback? onSelectAll,
+    required VoidCallback? onLookUp,
     required VoidCallback? onLiveTextInput,
     required this.anchors,
   }) : children = null,
@@ -103,6 +104,7 @@ class CupertinoAdaptiveTextSelectionToolbar extends StatelessWidget {
          onCut: onCut,
          onPaste: onPaste,
          onSelectAll: onSelectAll,
+         onLookUp: onLookUp,
          onLiveTextInput: onLiveTextInput
        );
 

packages/flutter/lib/src/cupertino/localizations.dart

@@ -245,6 +245,10 @@ abstract class CupertinoLocalizations {
   // The global version uses the translated string from the arb file.
   String get selectAllButtonLabel;
 
+  /// The term used for looking up a selection.
+  // The global version uses the translated string from the arb file.
+  String get lookUpButtonLabel;
+
   /// The default placeholder used in [CupertinoSearchTextField].
   // The global version uses the translated string from the arb file.
   String get searchTextFieldPlaceholderLabel;
@@ -455,6 +459,9 @@ class DefaultCupertinoLocalizations implements CupertinoLocalizations {
   @override
   String get selectAllButtonLabel => 'Select All';
 
+  @override
+  String get lookUpButtonLabel => 'Look Up';
+
   @override
   String get searchTextFieldPlaceholderLabel => 'Search';
 

packages/flutter/lib/src/cupertino/text_selection_toolbar_button.dart

@@ -105,6 +105,8 @@ class CupertinoTextSelectionToolbarButton extends StatefulWidget {
         return localizations.pasteButtonLabel;
       case ContextMenuButtonType.selectAll:
         return localizations.selectAllButtonLabel;
+      case ContextMenuButtonType.lookUp:
+        return localizations.lookUpButtonLabel;
       case ContextMenuButtonType.liveTextInput:
       case ContextMenuButtonType.delete:
       case ContextMenuButtonType.custom:
@@ -189,6 +191,7 @@ class _CupertinoTextSelectionToolbarButtonState extends State<CupertinoTextSelec
       case ContextMenuButtonType.paste:
       case ContextMenuButtonType.selectAll:
       case ContextMenuButtonType.delete:
+      case ContextMenuButtonType.lookUp:
       case ContextMenuButtonType.custom:
         return textWidget;
       case ContextMenuButtonType.liveTextInput:

packages/flutter/lib/src/material/adaptive_text_selection_toolbar.dart

@@ -103,6 +103,7 @@ class AdaptiveTextSelectionToolbar extends StatelessWidget {
     required VoidCallback? onCut,
     required VoidCallback? onPaste,
     required VoidCallback? onSelectAll,
+    required VoidCallback? onLookUp,
     required VoidCallback? onLiveTextInput,
     required this.anchors,
   }) : children = null,
@@ -112,6 +113,7 @@ class AdaptiveTextSelectionToolbar extends StatelessWidget {
          onCut: onCut,
          onPaste: onPaste,
          onSelectAll: onSelectAll,
+         onLookUp: onLookUp,
          onLiveTextInput: onLiveTextInput
        );
 
@@ -215,6 +217,8 @@ class AdaptiveTextSelectionToolbar extends StatelessWidget {
             return localizations.selectAllButtonLabel;
           case ContextMenuButtonType.delete:
             return localizations.deleteButtonTooltip.toUpperCase();
+          case ContextMenuButtonType.lookUp:
+            return localizations.lookUpButtonLabel;
           case ContextMenuButtonType.liveTextInput:
             return localizations.scanTextButtonLabel;
           case ContextMenuButtonType.custom:

packages/flutter/lib/src/material/material_localizations.dart

@@ -115,6 +115,9 @@ abstract class MaterialLocalizations {
   /// Label for "select all" edit buttons and menu items.
   String get selectAllButtonLabel;
 
+  /// Label for "look up" edit buttons and menu items.
+  String get lookUpButtonLabel;
+
   /// Label for the [AboutDialog] button that shows the [LicensePage].
   String get viewLicensesButtonLabel;
 
@@ -1178,6 +1181,9 @@ class DefaultMaterialLocalizations implements MaterialLocalizations {
   @override
   String get selectAllButtonLabel => 'Select all';
 
+  @override
+  String get lookUpButtonLabel => 'Look Up';
+
   @override
   String get viewLicensesButtonLabel => 'View licenses';
 

packages/flutter/lib/src/services/text_input.dart

@@ -1050,6 +1050,9 @@ mixin TextSelectionDelegate {
   /// Whether select all is enabled, must not be null.
   bool get selectAllEnabled => true;
 
+  /// Whether look up is enabled, must not be null.
+  bool get lookUpEnabled => true;
+
   /// Whether Live Text input is enabled.
   ///
   /// See also:

packages/flutter/lib/src/widgets/context_menu_button_item.dart

@@ -26,6 +26,9 @@ enum ContextMenuButtonType {
   /// A button that deletes the current text selection.
   delete,
 
+  /// A button that looks up the current text selection.
+  lookUp,
+
   /// A button for starting Live Text input.
   ///
   /// See also:

packages/flutter/lib/src/widgets/editable_text.dart

@@ -1852,6 +1852,7 @@ class EditableText extends StatefulWidget {
     required final VoidCallback? onCut,
     required final VoidCallback? onPaste,
     required final VoidCallback? onSelectAll,
+    required final VoidCallback? onLookUp,
     required final VoidCallback? onLiveTextInput,
   }) {
     final List<ContextMenuButtonItem> resultButtonItem = <ContextMenuButtonItem>[];
@@ -1882,6 +1883,11 @@ class EditableText extends StatefulWidget {
             onPressed: onSelectAll,
             type: ContextMenuButtonType.selectAll,
           ),
+        if (onLookUp != null)
+          ContextMenuButtonItem(
+            onPressed: onLookUp,
+            type: ContextMenuButtonType.lookUp,
+          ),
       ]);
     }
 
@@ -2232,6 +2238,15 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
     }
   }
 
+  @override
+  bool get lookUpEnabled {
+    if (defaultTargetPlatform != TargetPlatform.iOS) {
+      return false;
+    }
+    return !widget.obscureText
+        && !textEditingValue.selection.isCollapsed;
+  }
+
   @override
   bool get liveTextInputEnabled {
     return _liveTextInputStatus?.value == LiveTextInputStatus.enabled &&
@@ -2397,6 +2412,22 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
     }
   }
 
+  /// Look up the current selection, as in the "Look Up" edit menu button on iOS.
+  /// Currently this is only implemented for iOS.
+  /// Throws an error if the selection is empty or collapsed.
+  Future<void> lookUpSelection(SelectionChangedCause cause) async {
+    assert(!widget.obscureText);
+
+    final String text = textEditingValue.selection.textInside(textEditingValue.text);
+    if (widget.obscureText || text.isEmpty) {
+      return;
+    }
+    await SystemChannels.platform.invokeMethod(
+      'LookUp.invoke',
+      text,
+    );
+  }
+
   void _startLiveTextInput(SelectionChangedCause cause) {
     if (!liveTextInputEnabled) {
       return;
@@ -2623,6 +2654,9 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
       onSelectAll: selectAllEnabled
           ? () => selectAll(SelectionChangedCause.toolbar)
           : null,
+      onLookUp: lookUpEnabled
+          ? () => lookUpSelection(SelectionChangedCause.toolbar)
+          : null,
       onLiveTextInput: liveTextInputEnabled
           ? () => _startLiveTextInput(SelectionChangedCause.toolbar)
           : null,

packages/flutter/test/cupertino/adaptive_text_selection_toolbar_test.dart

@@ -168,6 +168,7 @@ void main() {
           onPaste: () {},
           onSelectAll: () {},
           onLiveTextInput: () {},
+          onLookUp: () {},
         ),
       ),
     ));
@@ -180,16 +181,16 @@ void main() {
 
     switch (defaultTargetPlatform) {
       case TargetPlatform.android:
-        expect(find.byType(CupertinoTextSelectionToolbarButton), findsNWidgets(5));
+        expect(find.byType(CupertinoTextSelectionToolbarButton), findsNWidgets(6));
       case TargetPlatform.fuchsia:
-        expect(find.byType(CupertinoTextSelectionToolbarButton), findsNWidgets(5));
+        expect(find.byType(CupertinoTextSelectionToolbarButton), findsNWidgets(6));
       case TargetPlatform.iOS:
-        expect(find.byType(CupertinoTextSelectionToolbarButton), findsNWidgets(5));
+        expect(find.byType(CupertinoTextSelectionToolbarButton), findsNWidgets(6));
         expect(findLiveTextButton(), findsOneWidget);
       case TargetPlatform.macOS:
       case TargetPlatform.linux:
       case TargetPlatform.windows:
-        expect(find.byType(CupertinoDesktopTextSelectionToolbarButton), findsNWidgets(5));
+        expect(find.byType(CupertinoDesktopTextSelectionToolbarButton), findsNWidgets(6));
     }
   },
     skip: kIsWeb, // [intended] on web the browser handles the context menu.