[SuperEditor][SuperReader] - Lock scrolling when content fits within available space (Resolves #1409)

super_editor/lib/src/default_editor/document_scrollable.dart

@@ -373,6 +373,11 @@ class AutoScrollController with ChangeNotifier {
     }
 
     final scrollPosition = _getScrollPosition!();
+
+    if (scrollPosition.maxScrollExtent == 0) {
+      return;
+    }
+
     scrollPosition.jumpTo(
       (scrollPosition.pixels + delta).clamp(0.0, scrollPosition.maxScrollExtent),
     );
@@ -388,7 +393,9 @@ class AutoScrollController with ChangeNotifier {
     }
 
     if (pos is ScrollPositionWithSingleContext) {
-      pos.goBallistic(pixelsPerSecond);
+      if (pos.maxScrollExtent > 0) {
+        pos.goBallistic(pixelsPerSecond);
+      }
       pos.context.setIgnorePointer(false);
     }
   }

super_editor/test/super_editor/supereditor_scrolling_test.dart

@@ -9,6 +9,7 @@ import 'package:super_editor/super_editor.dart';
 import 'package:super_editor/super_editor_test.dart';
 
 import 'supereditor_test_tools.dart';
+import 'test_documents.dart';
 
 void main() {
   group("SuperEditor scrolling", () {
@@ -682,11 +683,55 @@ void main() {
 
           // Ensure SuperEditor has scrolled
           expect(editorScrollController.offset, greaterThan(0));
-
-          // Ensure that scrolling didn't scroll the ListView
-          expect(listScrollController.position.pixels, equals(0));
         });
       });
+
+      group("doesn't scroll when content fits within the available space", () {
+        testWidgetsOnDesktop(
+          "attempt to scroll vertically in both directions",
+          (tester) async {
+            const windowSize = Size(800, 600);
+            tester.view.physicalSize = windowSize;
+
+            final isScrollingUp = _scrollDirectionVariant.currentValue == _ScrollDirection.up;
+
+            await tester //
+                .createDocument()
+                .withCustomContent(
+                  paragraphThenHrThenParagraphDoc()
+                    ..insertNodeAt(
+                      0,
+                      ParagraphNode(
+                        id: Editor.createNodeId(),
+                        text: AttributedText('Document #1'),
+                        metadata: {
+                          'blockType': header1Attribution,
+                        },
+                      ),
+                    ),
+                )
+                .pump();
+
+            final scrollState = tester.state<ScrollableState>(find.byType(Scrollable));
+
+            // Perform a fling on the editor to attemp scrolling.
+            await tester.trackpadFling(
+              find.byType(SuperEditor),
+              Offset(0.0, isScrollingUp ? 100 : -100),
+              300,
+            );
+
+            // Pump a few frames of momentum.
+            for (int i = 0; i < 5; i += 1) {
+              await tester.pump(const Duration(milliseconds: 16));
+            }
+
+            // Ensure SuperEditor is not scrolling.
+            expect(scrollState.position.activity?.isScrolling, false);
+          },
+          variant: _scrollDirectionVariant,
+        );
+      });
     });
   });
 }
@@ -850,3 +895,13 @@ MutableDocument _createExampleDocumentForScrolling() {
     ],
   );
 }
+
+final _scrollDirectionVariant = ValueVariant<_ScrollDirection>({
+  _ScrollDirection.up,
+  _ScrollDirection.down,
+});
+
+enum _ScrollDirection {
+  up,
+  down;
+}

super_editor/test/super_reader/super_reader_scrolling_test.dart

@@ -6,6 +6,7 @@ import 'package:super_editor/super_editor.dart';
 import 'package:super_editor/super_reader_test.dart';
 
 import 'reader_test_tools.dart';
+import 'test_documents.dart';
 
 void main() {
   group("SuperReader scrolling", () {
@@ -218,5 +219,62 @@ void main() {
         isTrue,
       );
     });
+
+    group("doesn't scroll when content fits within the available space", () {
+      testWidgetsOnDesktop(
+        "attempt to scroll vertically in both directions",
+        (tester) async {
+          const windowSize = Size(800, 600);
+          tester.view.physicalSize = windowSize;
+
+          final isScrollUp = _scrollDirectionVariant.currentValue == _ScrollDirection.up;
+
+          await tester //
+              .createDocument()
+              .withCustomContent(
+                paragraphThenHrThenParagraphDoc()
+                  ..insertNodeAt(
+                    0,
+                    ParagraphNode(
+                      id: Editor.createNodeId(),
+                      text: AttributedText('Document #1'),
+                      metadata: {
+                        'blockType': header1Attribution,
+                      },
+                    ),
+                  ),
+              )
+              .pump();
+
+          final scrollState = tester.state<ScrollableState>(find.byType(Scrollable));
+
+          // Perform a fling on the reader to attemp scrolling.
+          await tester.trackpadFling(
+            find.byType(SuperReader),
+            Offset(0.0, isScrollUp ? 100 : -100),
+            300,
+          );
+
+          // Pump a few frames of momentum.
+          for (int i = 0; i < 5; i += 1) {
+            await tester.pump(const Duration(milliseconds: 16));
+          }
+
+          // Ensure SuperReader is not scrolling.
+          expect(scrollState.position.activity?.isScrolling, false);
+        },
+        variant: _scrollDirectionVariant,
+      );
+    });
   });
 }
+
+final _scrollDirectionVariant = ValueVariant<_ScrollDirection>({
+  _ScrollDirection.up,
+  _ScrollDirection.down,
+});
+
+enum _ScrollDirection {
+  up,
+  down;
+}