Make buildHandle onTap optional (#84806)

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

@@ -67,7 +67,7 @@ class _CupertinoDesktopTextSelectionControls extends TextSelectionControls {
 
   /// Builds the text selection handles, but desktop has none.
   @override
-  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textLineHeight, VoidCallback? onTap) {
+  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textLineHeight, [VoidCallback? onTap]) {
     return const SizedBox.shrink();
   }
 

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

@@ -247,7 +247,7 @@ class CupertinoTextSelectionControls extends TextSelectionControls {
 
   /// Builder for iOS text selection edges.
   @override
-  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textLineHeight, VoidCallback? onTap) {
+  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textLineHeight, [VoidCallback? onTap]) {
     // iOS selection handles do not respond to taps.
 
     // We want a size that's a vertical line the height of the text plus a 18.0

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

@@ -53,7 +53,7 @@ class _DesktopTextSelectionControls extends TextSelectionControls {
 
   /// Builds the text selection handles, but desktop has none.
   @override
-  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textLineHeight, VoidCallback? onTap) {
+  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textLineHeight, [VoidCallback? onTap]) {
     return const SizedBox.shrink();
   }
 

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

@@ -54,7 +54,7 @@ class MaterialTextSelectionControls extends TextSelectionControls {
 
   /// Builder for material-style text selection handles.
   @override
-  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textHeight, VoidCallback? onTap) {
+  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textHeight, [VoidCallback? onTap]) {
     final ThemeData theme = Theme.of(context);
     final Color handleColor = TextSelectionTheme.of(context).selectionHandleColor ?? theme.colorScheme.primary;
     final Widget handle = SizedBox(

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

@@ -119,7 +119,7 @@ abstract class TextSelectionControls {
   /// interaction is allowed. As a counterexample, the default selection handle
   /// on iOS [cupertinoTextSelectionControls] does not call [onTap] at all,
   /// since its handles are not meant to be tapped.
-  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textLineHeight, VoidCallback? onTap);
+  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textLineHeight, [VoidCallback? onTap]);
 
   /// Get the anchor point of the handle relative to itself. The anchor point is
   /// the point that is aligned with a specific point in the text. A handle

packages/flutter/test/cupertino/text_field_test.dart

@@ -35,7 +35,7 @@ class MockClipboard {
 
 class MockTextSelectionControls extends TextSelectionControls {
   @override
-  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textLineHeight, VoidCallback? onTap) {
+  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textLineHeight, [VoidCallback? onTap]) {
     throw UnimplementedError();
   }
 

packages/flutter/test/material/text_selection_test.dart

@@ -581,6 +581,38 @@ void main() {
         matchesGoldenFile('transparent_handle.png'),
       );
     });
+
+    testWidgets('works with 3 positional parameters', (WidgetTester tester) async {
+      await tester.pumpWidget(Theme(
+        data: ThemeData(
+          textSelectionTheme: const TextSelectionThemeData(
+            selectionHandleColor: Color(0x550000AA),
+          ),
+        ),
+        child: Builder(
+          builder: (BuildContext context) {
+            return Container(
+              color: Colors.white,
+              height: 800,
+              width: 800,
+              child: Padding(
+                padding: const EdgeInsets.symmetric(horizontal: 250),
+                child: FittedBox(
+                  child: materialTextSelectionControls.buildHandle(
+                    context, TextSelectionHandleType.right, 10.0,
+                  ),
+                ),
+              ),
+            );
+          },
+        ),
+      ));
+
+      // No expect here as this should simply compile / not throw any
+      // exceptions while building. The test will fail if this either does
+      // not compile or if the tester catches an exception, which we do
+      // not take here.
+    });
   });
 
   testWidgets('Paste only appears when clipboard has contents', (WidgetTester tester) async {

packages/flutter/test/widgets/editable_text_test.dart

@@ -7569,7 +7569,7 @@ class MockTextSelectionControls extends Fake implements TextSelectionControls {
   }
 
   @override
-  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textLineHeight, VoidCallback? onTap) {
+  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textLineHeight, [VoidCallback? onTap]) {
     return Container();
   }