iOS TextSelectionToolbar fidelity (#127757)

CupertinoTextSelectionToolbar is different from the native one, with some UI and UX issues. More details on the linked issue.

https://github.com/flutter/flutter/issues/127756

Currently the only problem that I listed on the linked issue that I couldn't fix was the horizontal scrolling, but to workaround this I added a GestureDetector to change pages when swiping the toolbar. It's not exactly the same as native as there is no scroll animation, but it works.

I'm creating this PR a little early to have some feedback as these changes were more complex than the ones in my last PR. Probably best if @justinmc is involved 😅

|Version|Video|
|-|-|
|Flutter Old|<video src="https://github.com/flutter/flutter/assets/12024080/7cf81075-46ec-4970-b118-cc27b60ddac0"></video>|
|Flutter New|<video src="https://github.com/flutter/flutter/assets/12024080/c9e27a53-f94c-4cb0-9b76-e47b73841dcb"></video>|
|Native|<video src="https://github.com/flutter/flutter/assets/12024080/468c7d5b-ba93-4bd4-8f6e-8ec2644b9866"></video>|

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

@@ -11,30 +11,26 @@ import 'localizations.dart';
 
 const TextStyle _kToolbarButtonFontStyle = TextStyle(
   inherit: false,
-  fontSize: 14.0,
+  fontSize: 15.0,
   letterSpacing: -0.15,
   fontWeight: FontWeight.w400,
 );
 
-// Colors extracted from https://developer.apple.com/design/resources/.
-// TODO(LongCatIsLooong): https://github.com/flutter/flutter/issues/41507.
-const CupertinoDynamicColor _kToolbarBackgroundColor = CupertinoDynamicColor.withBrightness(
-  // This value was extracted from a screenshot of iOS 16.0.3, as light mode
-  // didn't appear in the Apple design resources assets linked above.
-  color: Color(0xEBF7F7F7),
-  darkColor: Color(0xEB202020),
-);
-
 const CupertinoDynamicColor _kToolbarTextColor = CupertinoDynamicColor.withBrightness(
   color: CupertinoColors.black,
   darkColor: CupertinoColors.white,
 );
 
-// Eyeballed value.
-const EdgeInsets _kToolbarButtonPadding = EdgeInsets.symmetric(vertical: 16.0, horizontal: 18.0);
+const CupertinoDynamicColor _kToolbarPressedColor = CupertinoDynamicColor.withBrightness(
+  color: Color(0x10000000),
+  darkColor: Color(0x10FFFFFF),
+);
+
+// Value measured from screenshot of iOS 16.0.2
+const EdgeInsets _kToolbarButtonPadding = EdgeInsets.symmetric(vertical: 18.0, horizontal: 16.0);
 
 /// A button in the style of the iOS text selection toolbar buttons.
-class CupertinoTextSelectionToolbarButton extends StatelessWidget {
+class CupertinoTextSelectionToolbarButton extends StatefulWidget {
   /// Create an instance of [CupertinoTextSelectionToolbarButton].
   ///
   /// [child] cannot be null.
@@ -113,26 +109,65 @@ class CupertinoTextSelectionToolbarButton extends StatelessWidget {
     }
   }
 
+  @override
+  State<StatefulWidget> createState() => _CupertinoTextSelectionToolbarButtonState();
+}
+
+class _CupertinoTextSelectionToolbarButtonState extends State<CupertinoTextSelectionToolbarButton> {
+  bool isPressed = false;
+
+  void _onTapDown(TapDownDetails details) {
+    setState(() => isPressed = true);
+  }
+
+  void _onTapUp(TapUpDetails details) {
+    setState(() => isPressed = false);
+    widget.onPressed?.call();
+  }
+
+  void _onTapCancel() {
+    setState(() => isPressed = false);
+  }
+
   @override
   Widget build(BuildContext context) {
-    final Widget child = this.child ?? Text(
-       text ?? getButtonLabel(context, buttonItem!),
+    final Widget child = CupertinoButton(
+      color: isPressed
+        ? _kToolbarPressedColor.resolveFrom(context)
+        : const Color(0x00000000),
+      borderRadius: null,
+      disabledColor: const Color(0x00000000),
+      // This CupertinoButton does not actually handle the onPressed callback,
+      // this is only here to correctly enable/disable the button (see
+      // GestureDetector comment below).
+      onPressed: widget.onPressed,
+      padding: _kToolbarButtonPadding,
+      // There's no foreground fade on iOS toolbar anymore, just the background
+      // is darkened.
+      pressedOpacity: 1.0,
+      child: widget.child ?? Text(
+         widget.text ?? CupertinoTextSelectionToolbarButton.getButtonLabel(context, widget.buttonItem!),
          overflow: TextOverflow.ellipsis,
          style: _kToolbarButtonFontStyle.copyWith(
-         color: onPressed != null
+           color: widget.onPressed != null
                ? _kToolbarTextColor.resolveFrom(context)
                : CupertinoColors.inactiveGray,
          ),
+       ),
     );
 
-    return CupertinoButton(
-      borderRadius: null,
-      color: _kToolbarBackgroundColor,
-      disabledColor: _kToolbarBackgroundColor,
-      onPressed: onPressed,
-      padding: _kToolbarButtonPadding,
-      pressedOpacity: onPressed == null ? 1.0 : 0.7,
+    if (widget.onPressed != null) {
+      // As it's needed to change the CupertinoButton's backgroundColor when
+      // pressed, not its opacity, this GestureDetector handles both the
+      // onPressed callback and the backgroundColor change.
+      return GestureDetector(
+        onTapDown: _onTapDown,
+        onTapUp: _onTapUp,
+        onTapCancel: _onTapCancel,
         child: child,
       );
+    } else {
+      return child;
+    }
   }
 }

packages/flutter/test/cupertino/text_field_test.dart

@@ -1545,7 +1545,7 @@ void main() {
 
     Text text = tester.widget<Text>(find.text('Paste'));
     expect(text.style!.color!.value, CupertinoColors.black.value);
-    expect(text.style!.fontSize, 14);
+    expect(text.style!.fontSize, 15);
     expect(text.style!.letterSpacing, -0.15);
     expect(text.style!.fontWeight, FontWeight.w400);
 
@@ -1577,7 +1577,7 @@ void main() {
     text = tester.widget<Text>(find.text('Paste'));
     // The toolbar buttons' text are still the same style.
     expect(text.style!.color!.value, CupertinoColors.white.value);
-    expect(text.style!.fontSize, 14);
+    expect(text.style!.fontSize, 15);
     expect(text.style!.letterSpacing, -0.15);
     expect(text.style!.fontWeight, FontWeight.w400);
   }, skip: isContextMenuProvidedByPlatform); // [intended] only applies to platforms where we supply the context menu.
@@ -6537,7 +6537,7 @@ void main() {
             topMatcher: moreOrLessEquals(bottomLeftSelectionPosition.dy + 8, epsilon: 0.01),
             leftMatcher: moreOrLessEquals(8),
             rightMatcher: lessThanOrEqualTo(400 - 8),
-            bottomMatcher: moreOrLessEquals(bottomLeftSelectionPosition.dy + 8 + 43, epsilon: 0.01),
+            bottomMatcher: moreOrLessEquals(bottomLeftSelectionPosition.dy + 8 + 45, epsilon: 0.01),
           ),
         ),
       );
@@ -6597,7 +6597,7 @@ void main() {
           pathMatcher: PathBoundsMatcher(
             topMatcher: moreOrLessEquals(bottomLeftSelectionPosition.dy + 8, epsilon: 0.01),
             rightMatcher: moreOrLessEquals(400.0 - 8),
-            bottomMatcher: moreOrLessEquals(bottomLeftSelectionPosition.dy + 8 + 43, epsilon: 0.01),
+            bottomMatcher: moreOrLessEquals(bottomLeftSelectionPosition.dy + 8 + 45, epsilon: 0.01),
             leftMatcher: greaterThanOrEqualTo(8),
           ),
         ),
@@ -6650,7 +6650,7 @@ void main() {
         paints..clipPath(
           pathMatcher: PathBoundsMatcher(
             bottomMatcher: moreOrLessEquals(bottomLeftSelectionPosition.dy - 8 - lineHeight, epsilon: 0.01),
-            topMatcher: moreOrLessEquals(bottomLeftSelectionPosition.dy - 8 - lineHeight - 43, epsilon: 0.01),
+            topMatcher: moreOrLessEquals(bottomLeftSelectionPosition.dy - 8 - lineHeight - 45, epsilon: 0.01),
             rightMatcher: lessThanOrEqualTo(400 - 8),
             leftMatcher: greaterThanOrEqualTo(8),
           ),
@@ -6719,7 +6719,7 @@ void main() {
         paints..clipPath(
           pathMatcher: PathBoundsMatcher(
             bottomMatcher: moreOrLessEquals(selectionPosition.dy - 8 - lineHeight, epsilon: 0.01),
-            topMatcher: moreOrLessEquals(selectionPosition.dy - 8 - lineHeight - 43, epsilon: 0.01),
+            topMatcher: moreOrLessEquals(selectionPosition.dy - 8 - lineHeight - 45, epsilon: 0.01),
             rightMatcher: lessThanOrEqualTo(400 - 8),
             leftMatcher: greaterThanOrEqualTo(8),
           ),
@@ -6792,7 +6792,7 @@ void main() {
         paints..clipPath(
           pathMatcher: PathBoundsMatcher(
             bottomMatcher: moreOrLessEquals(selectionPosition.dy - 8 - lineHeight, epsilon: 0.01),
-            topMatcher: moreOrLessEquals(selectionPosition.dy - 8 - lineHeight - 43, epsilon: 0.01),
+            topMatcher: moreOrLessEquals(selectionPosition.dy - 8 - lineHeight - 45, epsilon: 0.01),
             rightMatcher: lessThanOrEqualTo(400 - 8),
             leftMatcher: greaterThanOrEqualTo(8),
           ),

packages/flutter/test/cupertino/text_selection_toolbar_button_test.dart

@@ -29,7 +29,7 @@ void main() {
     expect(pressed, true);
   });
 
-  testWidgets('pressedOpacity defaults to 0.1', (WidgetTester tester) async {
+  testWidgets('background darkens when pressed', (WidgetTester tester) async {
     await tester.pumpWidget(
       CupertinoApp(
         home: Center(
@@ -41,35 +41,38 @@ void main() {
       ),
     );
 
-    // Original at full opacity.
-    FadeTransition opacity = tester.widget(find.descendant(
-      of: find.byType(CupertinoTextSelectionToolbarButton),
-      matching: find.byType(FadeTransition),
+    // Original with transparent background.
+    DecoratedBox decoratedBox = tester.widget(find.descendant(
+      of: find.byType(CupertinoButton),
+      matching: find.byType(DecoratedBox),
     ));
-    expect(opacity.opacity.value, 1.0);
+    BoxDecoration boxDecoration = decoratedBox.decoration as BoxDecoration;
+    expect(boxDecoration.color, const Color(0x00000000));
 
     // Make a "down" gesture on the button.
     final Offset center = tester.getCenter(find.byType(CupertinoTextSelectionToolbarButton));
     final TestGesture gesture = await tester.startGesture(center);
     await tester.pumpAndSettle();
 
-    // Opacity reduces during the down gesture.
-    opacity = tester.widget(find.descendant(
+    // When pressed, the background darkens.
+    decoratedBox = tester.widget(find.descendant(
       of: find.byType(CupertinoTextSelectionToolbarButton),
-      matching: find.byType(FadeTransition),
+      matching: find.byType(DecoratedBox),
     ));
-    expect(opacity.opacity.value, 0.7);
+    boxDecoration = decoratedBox.decoration as BoxDecoration;
+    expect(boxDecoration.color!.value, const Color(0x10000000).value);
 
     // Release the down gesture.
     await gesture.up();
     await tester.pumpAndSettle();
 
-    // Opacity is back to normal.
-    opacity = tester.widget(find.descendant(
+    // Color is back to transparent.
+    decoratedBox = tester.widget(find.descendant(
       of: find.byType(CupertinoTextSelectionToolbarButton),
-      matching: find.byType(FadeTransition),
+      matching: find.byType(DecoratedBox),
     ));
-    expect(opacity.opacity.value, 1.0);
+    boxDecoration = decoratedBox.decoration as BoxDecoration;
+    expect(boxDecoration.color, const Color(0x00000000));
   });
 
   testWidgets('passing null to onPressed disables the button', (WidgetTester tester) async {

packages/flutter/test/cupertino/text_selection_toolbar_test.dart

@@ -6,12 +6,13 @@ import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 
+import '../rendering/mock_canvas.dart';
 import '../widgets/editable_text_utils.dart' show textOffsetToPosition;
 
 // These constants are copied from cupertino/text_selection_toolbar.dart.
 const double _kArrowScreenPadding = 26.0;
 const double _kToolbarContentDistance = 8.0;
-const double _kToolbarHeight = 43.0;
+const double _kToolbarHeight = 45.0;
 
 // A custom text selection menu that just displays a single custom button.
 class _CustomCupertinoTextSelectionControls extends CupertinoTextSelectionControls {
@@ -60,9 +61,9 @@ class TestBox extends SizedBox {
   static const double itemWidth = 100.0;
 }
 
-const CupertinoDynamicColor _kToolbarBackgroundColor = CupertinoDynamicColor.withBrightness(
-  color: Color(0xEBF7F7F7),
-  darkColor: Color(0xEB202020),
+const CupertinoDynamicColor _kToolbarTextColor = CupertinoDynamicColor.withBrightness(
+  color: CupertinoColors.black,
+  darkColor: CupertinoColors.white,
 );
 
 void main() {
@@ -81,8 +82,65 @@ void main() {
   // visible part of the toolbar for use in measurements.
   Finder findToolbar() => findPrivate('_CupertinoTextSelectionToolbarContent');
 
-  Finder findOverflowNextButton() => find.text('▶');
-  Finder findOverflowBackButton() => find.text('◀');
+  // Check if the middle point of the chevron is pointing left or right.
+  //
+  // Offset.dx: a right or left margin (_kToolbarChevronSize / 4 => 2.5) to center the icon horizontally
+  // Offset.dy: always in the exact vertical center (_kToolbarChevronSize / 2 => 5)
+  PaintPattern overflowNextPaintPattern() => paints
+    ..line(p1: const Offset(2.5, 0), p2: const Offset(7.5, 5))
+    ..line(p1: const Offset(7.5, 5), p2: const Offset(2.5, 10));
+  PaintPattern overflowBackPaintPattern() => paints
+    ..line(p1: const Offset(7.5, 0), p2: const Offset(2.5, 5))
+    ..line(p1: const Offset(2.5, 5), p2: const Offset(7.5, 10));
+
+  Finder findOverflowNextButton() => find.byWidgetPredicate((Widget widget) =>
+    widget is CustomPaint &&
+    '${widget.painter?.runtimeType}' == '_RightCupertinoChevronPainter',
+  );
+  Finder findOverflowBackButton() => find.byWidgetPredicate((Widget widget) =>
+    widget is CustomPaint &&
+    '${widget.painter?.runtimeType}' == '_LeftCupertinoChevronPainter',
+  );
+
+  testWidgets('chevrons point to the correct side', (WidgetTester tester) async {
+    // Add enough TestBoxes to need 3 pages.
+    final List<Widget> children = List<Widget>.generate(15, (int i) => const TestBox());
+    await tester.pumpWidget(
+      CupertinoApp(
+        home: Center(
+          child: CupertinoTextSelectionToolbar(
+            anchorAbove: const Offset(50.0, 100.0),
+            anchorBelow: const Offset(50.0, 200.0),
+            children: children,
+          ),
+        ),
+      ),
+    );
+
+    expect(findOverflowBackButton(), findsNothing);
+    expect(findOverflowNextButton(), findsOneWidget);
+
+    expect(findOverflowNextButton(), overflowNextPaintPattern());
+
+    // Tap the overflow next button to show the next page of children.
+    await tester.tapAt(tester.getCenter(findOverflowNextButton()));
+    await tester.pumpAndSettle();
+
+    expect(findOverflowBackButton(), findsOneWidget);
+    expect(findOverflowNextButton(), findsOneWidget);
+
+    expect(findOverflowBackButton(), overflowBackPaintPattern());
+    expect(findOverflowNextButton(), overflowNextPaintPattern());
+
+    // Tap the overflow next button to show the last page of children.
+    await tester.tapAt(tester.getCenter(findOverflowNextButton()));
+    await tester.pumpAndSettle();
+
+    expect(findOverflowBackButton(), findsOneWidget);
+    expect(findOverflowNextButton(), findsNothing);
+
+    expect(findOverflowBackButton(), overflowBackPaintPattern());
+  }, skip: kIsWeb); // Path.combine is not implemented in the HTML backend https://github.com/flutter/flutter/issues/44572
 
   testWidgets('paginates children if they overflow', (WidgetTester tester) async {
     late StateSetter setState;
@@ -121,22 +179,15 @@ void main() {
     expect(findOverflowBackButton(), findsNothing);
 
     // Tap the overflow next button to show the next page of children.
-    await tester.tap(findOverflowNextButton());
-    await tester.pumpAndSettle();
-    expect(find.byType(TestBox), findsNWidgets(1));
-    expect(findOverflowNextButton(), findsOneWidget);
-    expect(findOverflowBackButton(), findsOneWidget);
-
-    // Tapping the overflow next button again does nothing because it is
-    // disabled and there are no more children to display.
-    await tester.tap(findOverflowNextButton());
+    // The next button is hidden as there's no next page.
+    await tester.tapAt(tester.getCenter(findOverflowNextButton()));
     await tester.pumpAndSettle();
     expect(find.byType(TestBox), findsNWidgets(1));
-    expect(findOverflowNextButton(), findsOneWidget);
+    expect(findOverflowNextButton(), findsNothing);
     expect(findOverflowBackButton(), findsOneWidget);
 
     // Tap the overflow back button to go back to the first page.
-    await tester.tap(findOverflowBackButton());
+    await tester.tapAt(tester.getCenter(findOverflowBackButton()));
     await tester.pumpAndSettle();
     expect(find.byType(TestBox), findsNWidgets(7));
     expect(findOverflowNextButton(), findsOneWidget);
@@ -157,7 +208,7 @@ void main() {
     expect(findOverflowBackButton(), findsNothing);
 
     // Tap the overflow next button to show the second page of children.
-    await tester.tap(findOverflowNextButton());
+    await tester.tapAt(tester.getCenter(findOverflowNextButton()));
     await tester.pumpAndSettle();
     // With the back button, only six children fit on this page.
     expect(find.byType(TestBox), findsNWidgets(6));
@@ -165,21 +216,21 @@ void main() {
     expect(findOverflowBackButton(), findsOneWidget);
 
     // Tap the overflow next button again to show the third page of children.
-    await tester.tap(findOverflowNextButton());
+    await tester.tapAt(tester.getCenter(findOverflowNextButton()));
     await tester.pumpAndSettle();
     expect(find.byType(TestBox), findsNWidgets(1));
-    expect(findOverflowNextButton(), findsOneWidget);
+    expect(findOverflowNextButton(), findsNothing);
     expect(findOverflowBackButton(), findsOneWidget);
 
     // Tap the overflow back button to go back to the second page.
-    await tester.tap(findOverflowBackButton());
+    await tester.tapAt(tester.getCenter(findOverflowBackButton()));
     await tester.pumpAndSettle();
     expect(find.byType(TestBox), findsNWidgets(6));
     expect(findOverflowNextButton(), findsOneWidget);
     expect(findOverflowBackButton(), findsOneWidget);
 
     // Tap the overflow back button to go back to the first page.
-    await tester.tap(findOverflowBackButton());
+    await tester.tapAt(tester.getCenter(findOverflowBackButton()));
     await tester.pumpAndSettle();
     expect(find.byType(TestBox), findsNWidgets(7));
     expect(findOverflowNextButton(), findsOneWidget);
@@ -345,13 +396,12 @@ void main() {
         final Finder buttonFinder = find.byType(CupertinoButton);
         expect(buttonFinder, findsOneWidget);
 
-        final Finder decorationFinder = find.descendant(
+        final Finder textFinder = find.descendant(
           of: find.byType(CupertinoButton),
-          matching: find.byType(DecoratedBox)
+          matching: find.byType(Text)
         );
-        expect(decorationFinder, findsOneWidget);
-        final DecoratedBox decoratedBox = tester.widget(decorationFinder);
-        final BoxDecoration boxDecoration = decoratedBox.decoration as BoxDecoration;
+        expect(textFinder, findsOneWidget);
+        final Text text = tester.widget(textFinder);
 
         // Theme brightness is preferred, otherwise MediaQuery brightness is
         // used. If both are null, defaults to light.
@@ -363,10 +413,10 @@ void main() {
         }
 
         expect(
-          boxDecoration.color!.value,
+          text.style!.color!.value,
           effectiveBrightness == Brightness.dark
-              ? _kToolbarBackgroundColor.darkColor.value
-              : _kToolbarBackgroundColor.color.value,
+              ? _kToolbarTextColor.darkColor.value
+              : _kToolbarTextColor.color.value,
         );
       }, skip: kIsWeb); // [intended] We do not use Flutter-rendered context menu on the Web.
     }
@@ -419,7 +469,7 @@ void main() {
       of: find.byType(CupertinoTextSelectionToolbar),
       matching: find.byType(DecoratedBox),
     );
-    expect(finder, findsNWidgets(2));
+    expect(finder, findsOneWidget);
     DecoratedBox decoratedBox = tester.widget(finder.first);
     BoxDecoration boxDecoration = decoratedBox.decoration as BoxDecoration;
     List<BoxShadow>? shadows = boxDecoration.boxShadow;