inset_shadow: Implement start/end shadows, not just top/bottom

Author: chrisbobbe

lib/widgets/inset_shadow.dart

@@ -17,6 +17,8 @@ class InsetShadowBox extends StatelessWidget {
     super.key,
     this.top = 0,
     this.bottom = 0,
+    this.start = 0,
+    this.end = 0,
     required this.color,
     required this.child,
   });
@@ -31,7 +33,17 @@ class InsetShadowBox extends StatelessWidget {
   /// This does not pad the child widget.
   final double bottom;
 
-  /// The shadow color to fade into transparency from the top and bottom borders.
+  /// The distance that the shadow from the child's start edge grows endwards.
+  ///
+  /// This does not pad the child widget.
+  final double start;
+
+  /// The distance that the shadow from the child's end edge grows startwards.
+  ///
+  /// This does not pad the child widget.
+  final double end;
+
+  /// The shadow color to fade into transparency from the edges, inward.
   final Color color;
 
   final Widget child;
@@ -50,10 +62,14 @@ class InsetShadowBox extends StatelessWidget {
       fit: StackFit.passthrough,
       children: [
         child,
-        Positioned(top: 0, height: top, left: 0, right: 0,
+        if (top != 0) Positioned(top: 0, height: top, left: 0, right: 0,
           child: DecoratedBox(decoration: _shadowFrom(Alignment.topCenter))),
-        Positioned(bottom: 0, height: bottom, left: 0, right: 0,
+        if (bottom != 0) Positioned(bottom: 0, height: bottom, left: 0, right: 0,
           child: DecoratedBox(decoration: _shadowFrom(Alignment.bottomCenter))),
+        if (start != 0) PositionedDirectional(start: 0, width: start, top: 0, bottom: 0,
+          child: DecoratedBox(decoration: _shadowFrom(AlignmentDirectional.centerStart))),
+        if (end != 0) PositionedDirectional(end: 0, width: end, top: 0, bottom: 0,
+          child: DecoratedBox(decoration: _shadowFrom(AlignmentDirectional.centerEnd))),
       ]);
   }
 }

test/widgets/inset_shadow_test.dart

@@ -16,7 +16,7 @@ void main() {
         // to ease the check on [Rect] later.
         alignment: Alignment.topLeft,
         child: SizedBox(width: 20, height: 20,
-          child: InsetShadowBox(top: 7, bottom: 3,
+          child: InsetShadowBox(top: 7, bottom: 3, start: 5, end: 6,
             color: Colors.red,
             child: SizedBox.shrink())))));
 
@@ -42,7 +42,7 @@ void main() {
     };
   }
 
-  testWidgets('render shadow correctly', (tester) async {
+  testWidgets('render shadow correctly: top/bottom', (tester) async {
     await tester.pumpWidget(const Directionality(
       textDirection: TextDirection.ltr,
       child: Center(
@@ -61,4 +61,33 @@ void main() {
       ..something(paintGradient(rect: const Rect.fromLTRB(0, 100-7, 100, 100)))
     ) as Matcher);
   });
+
+  final textDirectionVariant =
+    ValueVariant<TextDirection>({TextDirection.ltr, TextDirection.rtl});
+
+  testWidgets('render shadow correctly: start/end', (tester) async {
+    final textDirection = textDirectionVariant.currentValue!;
+    await tester.pumpWidget(Directionality(
+      textDirection: textDirection,
+      child: Center(
+        // This would be forced to fill up the screen
+        // if not wrapped in a widget like [Center].
+        child: SizedBox(width: 100, height: 100,
+          child: InsetShadowBox(start: 3, end: 7,
+            color: Colors.red,
+            child: SizedBox(width: 30, height: 30))))));
+
+    final box = tester.renderObject(find.byType(InsetShadowBox));
+    check(box).legacyMatcher(
+      // The coordinate system of these [Rect]'s is relative to the parent
+      // of the [Gradient] from [InsetShadowBox], not the entire [FlutterView].
+      switch (textDirection) {
+        TextDirection.ltr => paints
+          ..something(paintGradient(rect: Rect.fromLTRB(0, 0, 0+3, 100)))
+          ..something(paintGradient(rect: Rect.fromLTRB(100-7, 0, 100, 100))),
+        TextDirection.rtl => paints
+          ..something(paintGradient(rect: Rect.fromLTRB(100-3, 0, 100, 100)))
+          ..something(paintGradient(rect: Rect.fromLTRB(0, 0, 0+7, 100))),
+      } as Matcher);
+  }, variant: textDirectionVariant);
 }