fixes letsar#279

lib/src/dismissal.dart

@@ -1,3 +1,5 @@
+import 'dart:math' as math;
+
 import 'package:flutter/widgets.dart';
 
 import 'controller.dart';
@@ -90,10 +92,65 @@ class _SlidableDismissalState extends State<SlidableDismissal>
       }());
     }
 
-    return SizeTransition(
+    return _SizeTransition(
       sizeFactor: resizeAnimation,
       axis: widget.axis,
       child: widget.child,
     );
   }
 }
+
+/// We use a custom SizeTransition to not clip when the sizeFactor is 1.
+class _SizeTransition extends AnimatedWidget {
+  /// Creates a size transition.
+  ///
+  /// The [axis], [sizeFactor], and [axisAlignment] arguments must not be null.
+  /// The [axis] argument defaults to [Axis.vertical]. The [axisAlignment]
+  /// defaults to 0.0, which centers the child along the main axis during the
+  /// transition.
+  const _SizeTransition({
+    Key? key,
+    this.axis = Axis.vertical,
+    required Animation<double> sizeFactor,
+    this.child,
+  }) : super(key: key, listenable: sizeFactor);
+
+  /// [Axis.horizontal] if [sizeFactor] modifies the width, otherwise
+  /// [Axis.vertical].
+  final Axis axis;
+
+  /// The animation that controls the (clipped) size of the child.
+  ///
+  /// The width or height (depending on the [axis] value) of this widget will be
+  /// its intrinsic width or height multiplied by [sizeFactor]'s value at the
+  /// current point in the animation.
+  ///
+  /// If the value of [sizeFactor] is less than one, the child will be clipped
+  /// in the appropriate axis.
+  Animation<double> get sizeFactor => listenable as Animation<double>;
+
+  /// The widget below this widget in the tree.
+  ///
+  /// {@macro flutter.widgets.ProxyWidget.child}
+  final Widget? child;
+
+  @override
+  Widget build(BuildContext context) {
+    final value = math.max<double>(sizeFactor.value, 0);
+    final AlignmentDirectional alignment;
+    if (axis == Axis.vertical) {
+      alignment = const AlignmentDirectional(-1, 0);
+    } else {
+      alignment = const AlignmentDirectional(0, -1);
+    }
+    return ClipRect(
+      clipBehavior: value == 1 ? Clip.none : Clip.hardEdge,
+      child: Align(
+        alignment: alignment,
+        heightFactor: axis == Axis.vertical ? value : null,
+        widthFactor: axis == Axis.horizontal ? value : null,
+        child: child,
+      ),
+    );
+  }
+}