Dispatch drag cancel notification

fujidaiti · Jul 23, 2024 · 9c711a9 · 9c711a9
1 parent b7b2195
commit 9c711a9
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Showing 5 changed files with 107 additions and 32 deletions.
diff --git a/package/lib/src/foundation/sheet_activity.dart b/package/lib/src/foundation/sheet_activity.dart
@@ -281,6 +281,13 @@ class DragSheetActivity extends SheetActivity
       ..didDragEnd(details)
       ..goBallistic(details.velocityY);
   }
+
+  @override
+  void onDragCancel(SheetDragCancelDetails details) {
+    owner
+      ..didDragCancel()
+      ..goBallistic(0);
+  }
 }
 
 @internal

diff --git a/package/lib/src/foundation/sheet_drag.dart b/package/lib/src/foundation/sheet_drag.dart
@@ -214,12 +214,22 @@ class SheetDragEndDetails extends SheetDragDetails {
   }
 }
 
+/// Details for when a sheet drag is canceled.
+class SheetDragCancelDetails extends SheetDragDetails {
+  /// Creates details for when a sheet drag is canceled.
+  SheetDragCancelDetails({required super.axisDirection});
+}
+
 @internal
 abstract class SheetDragControllerTarget {
   VerticalDirection get dragAxisDirection;
+  // TODO: Rename to onDragUpdate.
   void applyUserDragUpdate(SheetDragUpdateDetails details);
+  // TODO: Rename to onDragEnd.
   void applyUserDragEnd(SheetDragEndDetails details);
 
+  void onDragCancel(SheetDragCancelDetails details);
+
   /// Returns the minimum number of pixels that the sheet being dragged
   /// will potentially consume for the given drag delta.
   ///
@@ -265,12 +275,18 @@ class SheetDragController implements Drag, ScrollActivityDelegate {
   /// to avoid duplicating the code of [ScrollDragController].
   late final ScrollDragController _impl;
 
+  // TODO: Remove unnecessary nullability.
   SheetDragControllerTarget? _target;
+
+  // TODO: Rename to _gestureProxy.
   SheetGestureTamperer? _gestureTamperer;
 
-  SheetDragDetails _lastDetails;
+  /// The details of the most recently observed drag event.
   SheetDragDetails get lastDetails => _lastDetails;
+  SheetDragDetails _lastDetails;
 
+  /// The most recently observed [DragStartDetails], [DragUpdateDetails], or
+  /// [DragEndDetails] object.
   dynamic get lastRawDetails => _impl.lastDetails;
 
   void updateTarget(SheetDragControllerTarget delegate) {
@@ -296,29 +312,29 @@ class SheetDragController implements Drag, ScrollActivityDelegate {
     _impl.cancel();
   }
 
-  /// Called by the [ScrollDragController] in [Drag.end] and [Drag.cancel].
+  /// Called by the [ScrollDragController] in either [ScrollDragController.end]
+  /// or [ScrollDragController.cancel].
   @override
   void goBallistic(double velocity) {
-    var details = switch (_impl.lastDetails) {
-      final DragEndDetails details => SheetDragEndDetails(
-          axisDirection: _target!.dragAxisDirection,
-          velocityX: details.velocity.pixelsPerSecond.dx,
-          velocityY: -1 * velocity,
-        ),
-      // Drag was canceled.
-      _ => SheetDragEndDetails(
-          axisDirection: _target!.dragAxisDirection,
-          velocityX: 0,
-          velocityY: 0,
-        ),
-    };
-
-    if (_gestureTamperer case final tamper?) {
-      details = tamper.tamperWithDragEnd(details);
+    if (_impl.lastDetails case final DragEndDetails rawDetails) {
+      var endDetails = SheetDragEndDetails(
+        axisDirection: _target!.dragAxisDirection,
+        velocityX: rawDetails.velocity.pixelsPerSecond.dx,
+        velocityY: -1 * velocity,
+      );
+      if (_gestureTamperer case final tamper?) {
+        endDetails = tamper.tamperWithDragEnd(endDetails);
+      }
+      _lastDetails = endDetails;
+      _target!.applyUserDragEnd(endDetails);
+    } else {
+      final cancelDetails = SheetDragCancelDetails(
+        axisDirection: _target!.dragAxisDirection,
+      );
+      _lastDetails = cancelDetails;
+      _gestureTamperer?.onDragCancel(cancelDetails);
+      _target!.onDragCancel(cancelDetails);
     }
-
-    _lastDetails = details;
-    _target!.applyUserDragEnd(details);
   }
 
   /// Called by the [ScrollDragController] in [Drag.update].
@@ -373,6 +389,18 @@ class SheetDragController implements Drag, ScrollActivityDelegate {
 
   @mustCallSuper
   void dispose() {
+    // If the controller is disposed without calling end() or cancel(),
+    // we assume that the drag has been canceled.
+    if (_lastDetails is! SheetDragCancelDetails &&
+        _lastDetails is! SheetDragEndDetails) {
+      final cancelDetails = SheetDragCancelDetails(
+        axisDirection: _target!.dragAxisDirection,
+      );
+      _lastDetails = cancelDetails;
+      _gestureTamperer?.onDragCancel(cancelDetails);
+      _target!.onDragCancel(cancelDetails);
+    }
+
     _target = null;
     _gestureTamperer = null;
     _impl.dispose();

diff --git a/package/lib/src/foundation/sheet_gesture_tamperer.dart b/package/lib/src/foundation/sheet_gesture_tamperer.dart
@@ -4,6 +4,7 @@ import 'package:meta/meta.dart';
 import 'sheet_drag.dart';
 
 // TODO: Expose this as a public API.
+// TODO: Rename to SheetGestureProxy.
 @internal
 class TamperSheetGesture extends StatefulWidget {
   const TamperSheetGesture({
@@ -54,6 +55,7 @@ class _TamperSheetGestureState extends State<TamperSheetGesture> {
   }
 }
 
+// TODO: Rename to SheetGestureProxyScope.
 class _TamperSheetGestureScope extends InheritedWidget {
   const _TamperSheetGestureScope({
     required this.tamperer,
@@ -68,6 +70,7 @@ class _TamperSheetGestureScope extends InheritedWidget {
 }
 
 // TODO: Expose this as a public API.
+// TODO: Rename to SheetGestureProxyMixin.
 @internal
 mixin SheetGestureTamperer {
   SheetGestureTamperer? _parent;
@@ -79,12 +82,14 @@ mixin SheetGestureTamperer {
 
   @useResult
   @mustCallSuper
+  // TODO: Rename to onDragStart.
   SheetDragStartDetails tamperWithDragStart(SheetDragStartDetails details) {
     return _parent?.tamperWithDragStart(details) ?? details;
   }
 
   @useResult
   @mustCallSuper
+  // TODO: Rename to onDragUpdate.
   SheetDragUpdateDetails tamperWithDragUpdate(
     SheetDragUpdateDetails details,
     Offset minPotentialDeltaConsumption,
@@ -100,7 +105,13 @@ mixin SheetGestureTamperer {
 
   @useResult
   @mustCallSuper
+  // TODO: Rename to onDragEnd.
   SheetDragEndDetails tamperWithDragEnd(SheetDragEndDetails details) {
     return _parent?.tamperWithDragEnd(details) ?? details;
   }
+
+  @mustCallSuper
+  void onDragCancel(SheetDragCancelDetails details) {
+    _parent?.onDragCancel(details);
+  }
 }
diff --git a/package/lib/src/modal/modal_sheet.dart b/package/lib/src/modal/modal_sheet.dart
@@ -302,28 +302,49 @@ class _SwipeDismissibleController with SheetGestureTamperer {
 
   @override
   SheetDragEndDetails tamperWithDragEnd(SheetDragEndDetails details) {
+    final wasHandled = _handleDragEnd(
+      velocity: details.velocity,
+      axisDirection: details.axisDirection,
+    );
+    return wasHandled
+        ? super.tamperWithDragEnd(details.copyWith(velocityX: 0, velocityY: 0))
+        : super.tamperWithDragEnd(details);
+  }
+
+  @override
+  void onDragCancel(SheetDragCancelDetails details) {
+    super.onDragCancel(details);
+    _handleDragEnd(
+      axisDirection: details.axisDirection,
+      velocity: Velocity.zero,
+    );
+  }
+
+  bool _handleDragEnd({
+    required Velocity velocity,
+    required VerticalDirection axisDirection,
+  }) {
     if (!_isUserGestureInProgress || transitionController.isAnimating) {
-      return super.tamperWithDragEnd(details);
+      return false;
     }
 
     final viewportHeight = _context.size!.height;
     final draggedDistance = viewportHeight * (1 - transitionController.value);
 
-    final velocity = switch (details.axisDirection) {
-      VerticalDirection.up =>
-        details.velocity.pixelsPerSecond.dy / viewportHeight,
+    final effectiveVelocity = switch (axisDirection) {
+      VerticalDirection.up => velocity.pixelsPerSecond.dy / viewportHeight,
       VerticalDirection.down =>
-        -1 * details.velocity.pixelsPerSecond.dy / viewportHeight,
+        -1 * velocity.pixelsPerSecond.dy / viewportHeight,
     };
 
     final bool invokePop;
     if (MediaQuery.viewInsetsOf(_context).bottom > 0) {
       // The on-screen keyboard is open.
       invokePop = false;
-    } else if (velocity < 0) {
+    } else if (effectiveVelocity < 0) {
       // Flings down.
-      invokePop = velocity.abs() > _minFlingVelocityToDismiss;
-    } else if (velocity.isApprox(0)) {
+      invokePop = effectiveVelocity.abs() > _minFlingVelocityToDismiss;
+    } else if (effectiveVelocity.isApprox(0)) {
       assert(draggedDistance >= 0);
       // Dragged down enough to dismiss.
       invokePop = draggedDistance > _minDragDistanceToDismiss;
@@ -372,8 +393,6 @@ class _SwipeDismissibleController with SheetGestureTamperer {
       route.onPopInvoked(didPop);
     }
 
-    return super.tamperWithDragEnd(
-      details.copyWith(velocityX: 0, velocityY: 0),
-    );
+    return true;
   }
 }
diff --git a/package/lib/src/scrollable/scrollable_sheet_activity.dart b/package/lib/src/scrollable/scrollable_sheet_activity.dart
@@ -211,6 +211,16 @@ class DragScrollDrivenSheetActivity extends ScrollableSheetActivity
         scrollPosition: scrollPosition,
       );
   }
+
+  @override
+  void onDragCancel(SheetDragCancelDetails details) {
+    owner
+      ..didDragCancel()
+      ..goBallisticWithScrollPosition(
+        velocity: 0,
+        scrollPosition: scrollPosition,
+      );
+  }
 }
 
 /// A [SheetActivity] that animates either a scrollable content of