fix autoscrolling for non standard orientations

.github/workflows/build.yml

@@ -25,18 +25,14 @@ jobs:
       - name: Install dependencies
         run: flutter pub get
 
-      # Uncomment this step to verify the use of 'dart format' on each commit.
-      # - name: Verify formatting
-      #   run: dart format --output=none --set-exit-if-changed .
+      - name: Verify formatting
+         run: dart format --output=none --set-exit-if-changed .
 
-      # Your project will need to have tests in test/ and a dependency on
-      # package:test for this step to succeed. Note that Flutter projects will
-      # want to change this to 'flutter test'.
       - name: Run tests
         run: flutter test --coverage
 
-      - uses: codecov/codecov-action@v1
-        with:
-          token: ${{ secrets.CODECOV_TOKEN }} # not required for public repos   
-          verbose: true # optional (default = false)
+    #  - uses: codecov/codecov-action@v1
+    #  with:
+    #      token: ${{ secrets.CODECOV_TOKEN }} # not required for public repos   
+    #      verbose: true # optional (default = false)
 

lib/src/reorderable_grid.dart

@@ -263,8 +263,10 @@ class ReorderableGridState extends State<ReorderableGrid> {
             itemCount: widget.itemCount,
             onReorder: widget.onReorder,
             proxyDecorator: widget.proxyDecorator,
+            reverse: widget.reverse,
             autoScroll: widget.autoScroll ??
                 widget.physics is! NeverScrollableScrollPhysics,
+            scrollDirection: widget.scrollDirection,
           ),
         ),
       ],
@@ -303,8 +305,10 @@ class SliverReorderableGrid extends StatefulWidget {
     required this.itemCount,
     required this.onReorder,
     required this.gridDelegate,
+    this.reverse = false,
     this.proxyDecorator,
     this.autoScroll = true,
+    this.scrollDirection = Axis.vertical,
   })  : assert(itemCount >= 0),
         super(key: key);
 
@@ -326,6 +330,12 @@ class SliverReorderableGrid extends StatefulWidget {
   /// physics are [NeverScrollableScrollPhysics]
   final bool autoScroll;
 
+  /// {@macro flutter.widgets.scroll_view.reverse}
+  final bool reverse;
+
+  /// {@macro flutter.widgets.scroll_view.scrollDirection}
+  final Axis scrollDirection;
+
   @override
   SliverReorderableGridState createState() => SliverReorderableGridState();
 
@@ -357,11 +367,8 @@ class SliverReorderableGrid extends StatefulWidget {
             'No SliverReorderableGrid ancestor could be found starting from the context that was passed to SliverReorderableGrid.of().',
           ),
           ErrorHint(
-            'This can happen when the context provided is from the same StatefulWidget that '
-            'built the SliverReorderableGrid. Please see the SliverReorderableGrid documentation for examples '
-            'of how to refer to an SliverReorderableGrid object:\n'
-            '  https://api.flutter.dev/flutter/widgets/SliverReorderableGridState-class.html',
-          ),
+              'This can happen when the context provided is from the same StatefulWidget that '
+              'built the SliverReorderableGrid. Please see the SliverReorderableGrid documentation for examples'),
           context.describeElement('The context used was'),
         ]);
       }
@@ -608,35 +615,70 @@ class SliverReorderableGridState extends State<SliverReorderableGrid>
       return;
     }
 
-    final ScrollPosition position = _dragInfo!.scrollable!.position;
+    final position = _dragInfo!.scrollable!.position;
     double? newOffset;
 
-    const Duration duration = Duration(milliseconds: 14);
-    const double step = 1.0;
-    const double overDragMax = 20.0;
-    const double overDragCoef = 10;
+    const duration = Duration(milliseconds: 14);
+    const step = 1.0;
+    const overDragMax = 20.0;
+    const overDragCoef = 10;
+
+    final isVertical = widget.scrollDirection == Axis.vertical;
+    final isReversed = widget.reverse;
 
-    final RenderBox scrollRenderBox =
+    /// get the scroll window position on the screen
+    final scrollRenderBox =
         _dragInfo!.scrollable!.context.findRenderObject()! as RenderBox;
-    final Offset scrollOrigin = scrollRenderBox.localToGlobal(Offset.zero);
-
-    final scrollStart = scrollOrigin.dy;
-    final scrollEnd = scrollStart + scrollRenderBox.size.height;
-
-    final double proxyStart =
-        (_dragInfo!.dragPosition - _dragInfo!.dragOffset).dy;
-    final double proxyEnd = proxyStart + _dragInfo!.itemSize.height;
-
-    if (proxyStart < scrollStart &&
-        position.pixels > position.minScrollExtent) {
-      final double overDrag = max(scrollStart - proxyStart, overDragMax);
-      newOffset = max(position.minScrollExtent,
-          position.pixels - step * overDrag / overDragCoef);
-    } else if (proxyEnd > scrollEnd &&
-        position.pixels < position.maxScrollExtent) {
-      final double overDrag = max(proxyEnd - scrollEnd, overDragMax);
-      newOffset = min(position.maxScrollExtent,
-          position.pixels + step * overDrag / overDragCoef);
+    final Offset scrollPosition = scrollRenderBox.localToGlobal(Offset.zero);
+
+    /// calculate the start and end position for the scroll window
+    double scrollWindowStart =
+        isVertical ? scrollPosition.dy : scrollPosition.dx;
+    double scrollWindowEnd = scrollWindowStart +
+        (isVertical ? scrollRenderBox.size.height : scrollRenderBox.size.width);
+
+    /// get the proxy (dragged) object's position on the screen
+    final proxyObjectPosition = _dragInfo!.dragPosition - _dragInfo!.dragOffset;
+
+    /// calculate the start and end position for the proxy object
+    double proxyObjectStart =
+        isVertical ? proxyObjectPosition.dy : proxyObjectPosition.dx;
+    double proxyObjectEnd = proxyObjectStart +
+        (isVertical ? _dragInfo!.itemSize.height : _dragInfo!.itemSize.width);
+
+
+    if (!isReversed) {
+      /// if start of proxy object is before scroll window
+      if (proxyObjectStart < scrollWindowStart &&
+          position.pixels > position.minScrollExtent) {
+        final overDrag = max(scrollWindowStart - proxyObjectStart, overDragMax);
+        newOffset = max(position.minScrollExtent,
+            position.pixels - step * overDrag / overDragCoef);
+      }
+
+      /// if end of proxy object is after scroll window
+      else if (proxyObjectEnd > scrollWindowEnd &&
+          position.pixels < position.maxScrollExtent) {
+        final overDrag = max(proxyObjectEnd - scrollWindowEnd, overDragMax);
+        newOffset = min(position.maxScrollExtent,
+            position.pixels + step * overDrag / overDragCoef);
+      }
+    } else {
+      /// if start of proxy object is before scroll window
+      if (proxyObjectStart < scrollWindowStart &&
+          position.pixels < position.maxScrollExtent) {
+        final overDrag = max(scrollWindowStart - proxyObjectStart, overDragMax);
+        newOffset = max(position.minScrollExtent,
+            position.pixels + step * overDrag / overDragCoef);
+      }
+
+      /// if end of proxy object is after scroll window
+      else if (proxyObjectEnd > scrollWindowEnd &&
+          position.pixels > position.minScrollExtent) {
+        final overDrag = max(proxyObjectEnd - scrollWindowEnd, overDragMax);
+        newOffset = min(position.maxScrollExtent,
+            position.pixels - step * overDrag / overDragCoef);
+      }
     }
 
     if (newOffset != null && (newOffset - position.pixels).abs() >= 1.0) {

lib/src/reorderable_grid_view.dart

@@ -635,6 +635,8 @@ class _ReorderableGridViewState extends State<ReorderableGridView> {
             proxyDecorator: widget.proxyDecorator ?? _proxyDecorator,
             autoScroll: widget.autoScroll ??
                 widget.physics is! NeverScrollableScrollPhysics,
+            scrollDirection: widget.scrollDirection,
+            reverse: widget.reverse,
           ),
         ),
       ],

test/src/reorderable_grid_test.dart

@@ -408,6 +408,7 @@ class _TestGridState extends State<TestGrid> {
                       gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                         crossAxisCount: widget.crossAxisCount,
                       ),
+                      reverse: widget.reverse,
                       itemBuilder: (BuildContext context, int index) {
                         return Container(
                           key: ValueKey<int>(items[index]),

test/src/reorderable_grid_view_test.dart

@@ -6,44 +6,48 @@ import 'package:reorderable_grid/reorderable_grid.dart';
 void main() {
   const double itemHeight = 48.0;
 
-  testWidgets('ReorderableGridView.builder asserts on negative childCount',
-      (WidgetTester tester) async {
-    expect(
-        () => ReorderableGridView.builder(
-              gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
-                crossAxisCount: 4,
+  testWidgets(
+    'ReorderableGridView.builder asserts on negative childCount',
+    (WidgetTester tester) async {
+      expect(
+          () => ReorderableGridView.builder(
+                gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
+                  crossAxisCount: 4,
+                ),
+                itemBuilder: (BuildContext context, int index) {
+                  return const SizedBox();
+                },
+                itemCount: -1,
+                onReorder: (int from, int to) {},
               ),
-              itemBuilder: (BuildContext context, int index) {
-                return const SizedBox();
-              },
-              itemCount: -1,
-              onReorder: (int from, int to) {},
-            ),
-        throwsAssertionError);
-  });
+          throwsAssertionError);
+    },
+  );
 
-  testWidgets('ReorderableGridView.builder only creates the children it needs',
-      (WidgetTester tester) async {
-    final Set<int> itemsCreated = <int>{};
-    await tester.pumpWidget(MaterialApp(
-      home: ReorderableGridView.builder(
-        gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
-          crossAxisCount: 4,
+  testWidgets(
+    'ReorderableGridView.builder only creates the children it needs',
+    (WidgetTester tester) async {
+      final Set<int> itemsCreated = <int>{};
+      await tester.pumpWidget(MaterialApp(
+        home: ReorderableGridView.builder(
+          gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
+            crossAxisCount: 4,
+          ),
+          itemBuilder: (BuildContext context, int index) {
+            itemsCreated.add(index);
+            return Text(index.toString(), key: ValueKey<int>(index));
+          },
+          itemCount: 1000,
+          onReorder: (int from, int to) {},
         ),
-        itemBuilder: (BuildContext context, int index) {
-          itemsCreated.add(index);
-          return Text(index.toString(), key: ValueKey<int>(index));
-        },
-        itemCount: 1000,
-        onReorder: (int from, int to) {},
-      ),
-    ));
-
-    expect(itemsCreated, <int>{
-      ...{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
-      ...{10, 11, 12, 13, 14, 15, 16, 17, 18, 19},
-    });
-  });
+      ));
+
+      expect(itemsCreated, <int>{
+        ...{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
+        ...{10, 11, 12, 13, 14, 15, 16, 17, 18, 19},
+      });
+    },
+  );
 
   testWidgets('Animation test when placing an item in place',
       (WidgetTester tester) async {