Consider Scrollable location in text selection drag events (#102992)

Fixes scrolling by dragging a selection when the field is in a Scrollable.

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

@@ -923,7 +923,9 @@ class _CupertinoTextFieldState extends State<CupertinoTextField> with Restoratio
   @override
   void initState() {
     super.initState();
-    _selectionGestureDetectorBuilder = _CupertinoTextFieldSelectionGestureDetectorBuilder(state: this);
+    _selectionGestureDetectorBuilder = _CupertinoTextFieldSelectionGestureDetectorBuilder(
+      state: this,
+    );
     if (widget.controller == null) {
       _createLocalController();
     }

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

@@ -500,7 +500,9 @@ class _SelectableTextState extends State<SelectableText> implements TextSelectio
   @override
   void initState() {
     super.initState();
-    _selectionGestureDetectorBuilder = _SelectableTextSelectionGestureDetectorBuilder(state: this);
+    _selectionGestureDetectorBuilder = _SelectableTextSelectionGestureDetectorBuilder(
+      state: this,
+    );
     _controller = _TextSpanEditingController(
         textSpan: widget.textSpan ?? TextSpan(text: widget.data),
     );

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

@@ -2862,6 +2862,16 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
 
       final RevealedOffset targetOffset = _getOffsetToRevealCaret(_currentCaretRect!);
 
+      final Rect rectToReveal;
+      final TextSelection selection = textEditingValue.selection;
+      if (selection.isCollapsed) {
+        rectToReveal = targetOffset.rect;
+      } else {
+        final List<Rect> selectionBoxes = renderEditable.getBoxesForSelection(selection);
+        rectToReveal = selection.baseOffset < selection.extentOffset ?
+          selectionBoxes.last : selectionBoxes.first;
+      }
+
       if (withAnimation) {
         _scrollController.animateTo(
           targetOffset.offset,
@@ -2869,15 +2879,17 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
           curve: _caretAnimationCurve,
         );
         renderEditable.showOnScreen(
-          rect: caretPadding.inflateRect(targetOffset.rect),
+          rect: caretPadding.inflateRect(rectToReveal),
           duration: _caretAnimationDuration,
           curve: _caretAnimationCurve,
         );
       } else {
         _scrollController.jumpTo(targetOffset.offset);
-        renderEditable.showOnScreen(
-          rect: caretPadding.inflateRect(targetOffset.rect),
-        );
+        if (_value.selection.isCollapsed) {
+          renderEditable.showOnScreen(
+            rect: caretPadding.inflateRect(rectToReveal),
+          );
+        }
       }
     });
   }

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

@@ -22,6 +22,7 @@ import 'framework.dart';
 import 'gesture_detector.dart';
 import 'magnifier.dart';
 import 'overlay.dart';
+import 'scrollable.dart';
 import 'tap_region.dart';
 import 'ticker_provider.dart';
 import 'transitions.dart';
@@ -1714,7 +1715,11 @@ class TextSelectionGestureDetectorBuilder {
   @protected
   RenderEditable get renderEditable => editableText.renderEditable;
 
-  // The viewport offset pixels of the [RenderEditable] at the last drag start.
+  /// The viewport offset pixels of any [Scrollable] containing the
+  /// [RenderEditable] at the last drag start.
+  double _dragStartScrollOffset = 0.0;
+
+  /// The viewport offset pixels of the [RenderEditable] at the last drag start.
   double _dragStartViewportOffset = 0.0;
 
   // Returns true iff either shift key is currently down.
@@ -1726,6 +1731,16 @@ class TextSelectionGestureDetectorBuilder {
       }.contains);
   }
 
+  double get _scrollPosition {
+    final ScrollableState? scrollableState =
+        delegate.editableTextKey.currentContext == null
+            ? null
+            : Scrollable.of(delegate.editableTextKey.currentContext!);
+    return scrollableState == null
+        ? 0.0
+        : scrollableState.position.pixels;
+  }
+
   // True iff a tap + shift has been detected but the tap has not yet come up.
   bool _isShiftTapping = false;
 
@@ -2114,6 +2129,7 @@ class TextSelectionGestureDetectorBuilder {
       );
     }
 
+    _dragStartScrollOffset = _scrollPosition;
     _dragStartViewportOffset = renderEditable.offset.pixels;
   }
 
@@ -2134,12 +2150,15 @@ class TextSelectionGestureDetectorBuilder {
 
     if (!_isShiftTapping) {
       // Adjust the drag start offset for possible viewport offset changes.
-      final Offset startOffset = renderEditable.maxLines == 1
+      final Offset editableOffset = renderEditable.maxLines == 1
           ? Offset(renderEditable.offset.pixels - _dragStartViewportOffset, 0.0)
           : Offset(0.0, renderEditable.offset.pixels - _dragStartViewportOffset);
-
+      final Offset scrollableOffset = Offset(
+        0.0,
+        _scrollPosition - _dragStartScrollOffset,
+      );
       return renderEditable.selectPositionAt(
-        from: startDetails.globalPosition - startOffset,
+        from: startDetails.globalPosition - editableOffset - scrollableOffset,
         to: updateDetails.globalPosition,
         cause: SelectionChangedCause.drag,
       );

packages/flutter/test/widgets/text_selection_test.dart

@@ -79,8 +79,9 @@ void main() {
       forcePressEnabled: forcePressEnabled,
       selectionEnabled: selectionEnabled,
     );
+
     final TextSelectionGestureDetectorBuilder provider =
-    TextSelectionGestureDetectorBuilder(delegate: delegate);
+      TextSelectionGestureDetectorBuilder(delegate: delegate);
 
     await tester.pumpWidget(
       MaterialApp(
@@ -1329,6 +1330,160 @@ void main() {
       });
     });
   });
+
+  testWidgets('Mouse edge scrolling works in an outer scrollable', (WidgetTester tester) async {
+    // Regression test for https://github.com/flutter/flutter/issues/102484
+    final TextEditingController controller = TextEditingController(
+      text: 'I love flutter!\n' * 8,
+    );
+    final GlobalKey<EditableTextState> editableTextKey = GlobalKey<EditableTextState>();
+    final FakeTextSelectionGestureDetectorBuilderDelegate delegate = FakeTextSelectionGestureDetectorBuilderDelegate(
+      editableTextKey: editableTextKey,
+      forcePressEnabled: false,
+      selectionEnabled: true,
+    );
+
+    final ScrollController scrollController = ScrollController();
+    const double kLineHeight = 16.0;
+    final TextSelectionGestureDetectorBuilder provider =
+        TextSelectionGestureDetectorBuilder(
+          delegate: delegate,
+        );
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: SizedBox(
+            // Only 4 lines visible of 8 given.
+            height: kLineHeight * 4,
+            child: SingleChildScrollView(
+              controller: scrollController,
+              child: provider.buildGestureDetector(
+                behavior: HitTestBehavior.translucent,
+                child: EditableText(
+                  key: editableTextKey,
+                  controller: controller,
+                  focusNode: FocusNode(),
+                  backgroundCursorColor: Colors.white,
+                  cursorColor: Colors.white,
+                  style: const TextStyle(),
+                  selectionControls: materialTextSelectionControls,
+                  // EditableText will expand to the full 8 line height and will
+                  // not scroll itself.
+                  maxLines: null,
+                ),
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+
+    expect(controller.selection.isCollapsed, isTrue);
+    expect(controller.selection.baseOffset, -1);
+    expect(scrollController.position.pixels, 0.0);
+
+    final Offset position = textOffsetToPosition(tester, 4);
+
+    await tester.tapAt(position);
+    await tester.pump();
+
+    expect(controller.selection.isCollapsed, isTrue);
+    expect(controller.selection.baseOffset, 4);
+
+    // Select all text with the mouse.
+    final TestGesture gesture = await tester.startGesture(position, kind: PointerDeviceKind.mouse);
+    addTearDown(gesture.removePointer);
+    await tester.pump();
+    await gesture.moveTo(textOffsetToPosition(tester, (controller.text.length / 2).floor()));
+    await tester.pump();
+    await gesture.moveTo(textOffsetToPosition(tester, controller.text.length));
+    await tester.pump();
+    await gesture.up();
+    await tester.pumpAndSettle();
+
+    expect(controller.selection.isCollapsed, isFalse);
+    expect(controller.selection.baseOffset, 4);
+    expect(controller.selection.extentOffset, controller.text.length);
+    expect(scrollController.position.pixels, scrollController.position.maxScrollExtent);
+  });
+
+  testWidgets('Mouse edge scrolling works with both an outer scrollable and scrolling in the EditableText', (WidgetTester tester) async {
+    // Regression test for https://github.com/flutter/flutter/issues/102484
+    final TextEditingController controller = TextEditingController(
+      text: 'I love flutter!\n' * 8,
+    );
+    final GlobalKey<EditableTextState> editableTextKey = GlobalKey<EditableTextState>();
+    final FakeTextSelectionGestureDetectorBuilderDelegate delegate = FakeTextSelectionGestureDetectorBuilderDelegate(
+      editableTextKey: editableTextKey,
+      forcePressEnabled: false,
+      selectionEnabled: true,
+    );
+
+    final ScrollController scrollController = ScrollController();
+    const double kLineHeight = 16.0;
+    final TextSelectionGestureDetectorBuilder provider =
+        TextSelectionGestureDetectorBuilder(
+          delegate: delegate,
+        );
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: SizedBox(
+            // Only 4 lines visible of 8 given.
+            height: kLineHeight * 4,
+            child: SingleChildScrollView(
+              controller: scrollController,
+              child: provider.buildGestureDetector(
+                behavior: HitTestBehavior.translucent,
+                child: EditableText(
+                  key: editableTextKey,
+                  controller: controller,
+                  focusNode: FocusNode(),
+                  backgroundCursorColor: Colors.white,
+                  cursorColor: Colors.white,
+                  style: const TextStyle(),
+                  selectionControls: materialTextSelectionControls,
+                  // EditableText is taller than the SizedBox but not taller
+                  // than the text.
+                  maxLines: 6,
+                ),
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+
+    expect(controller.selection.isCollapsed, isTrue);
+    expect(controller.selection.baseOffset, -1);
+    expect(scrollController.position.pixels, 0.0);
+
+    final Offset position = textOffsetToPosition(tester, 4);
+
+    await tester.tapAt(position);
+    await tester.pump();
+
+    expect(controller.selection.isCollapsed, isTrue);
+    expect(controller.selection.baseOffset, 4);
+
+    // Select all text with the mouse.
+    final TestGesture gesture = await tester.startGesture(position, kind: PointerDeviceKind.mouse);
+    addTearDown(gesture.removePointer);
+    await tester.pump();
+    await gesture.moveTo(textOffsetToPosition(tester, (controller.text.length / 2).floor()));
+    await tester.pump();
+    await gesture.moveTo(textOffsetToPosition(tester, controller.text.length));
+    await tester.pump();
+    await gesture.up();
+    await tester.pumpAndSettle();
+
+    expect(controller.selection.isCollapsed, isFalse);
+    expect(controller.selection.baseOffset, 4);
+    expect(controller.selection.extentOffset, controller.text.length);
+    expect(scrollController.position.pixels, scrollController.position.maxScrollExtent);
+  });
 }
 
 class FakeTextSelectionGestureDetectorBuilderDelegate implements TextSelectionGestureDetectorBuilderDelegate {