Expose scroll position and layout measurements on CategoryOverflowCalendarDayView

lib/calendar_day_view.dart

@@ -6,12 +6,15 @@
 /// in the app that need better day view
 library calendar_day_view;
 
+export 'package:linked_scroll_controller/linked_scroll_controller.dart'
+    show LinkedScrollControllerGroup;
+
+export 'src/day_views/calendar_day_view_base.dart';
+export 'src/day_views/category/category_overflow_calendar_day_view.dart';
 export 'src/day_views/event_calendar_day_view.dart';
 export 'src/day_views/in_row_calendar_day_view.dart';
 export 'src/day_views/overflow/overflow_calendar_day_view.dart';
-export 'src/day_views/category/category_overflow_calendar_day_view.dart';
-export 'src/models/day_event.dart';
 export 'src/models/categorized_day_event.dart';
+export 'src/models/day_event.dart';
 export 'src/models/event_category.dart';
 export 'src/models/typedef.dart';
-export 'src/day_views/calendar_day_view_base.dart';

lib/src/day_views/category/category_overflow_calendar_day_view.dart

@@ -4,7 +4,6 @@ import 'package:calendar_day_view/src/extensions/list_extensions.dart';
 import 'package:calendar_day_view/src/extensions/time_of_day_extension.dart';
 import 'package:calendar_day_view/src/widgets/timed_rebuilder.dart';
 import 'package:flutter/material.dart';
-import 'package:linked_scroll_controller/linked_scroll_controller.dart';
 import 'package:timezone/timezone.dart';
 
 import '../../../calendar_day_view.dart';
@@ -21,13 +20,49 @@ typedef TitleRowBuilder = Widget Function({
   Widget? logo,
 });
 
+typedef CategoryDayViewLayoutMetricsCallback = void Function(
+  CategoryDayViewLayoutMetrics metrics,
+);
+
+@immutable
+class CategoryDayViewLayoutMetrics {
+  final Size bodyContentSize;
+  final Rect bodyViewport;
+
+  bool get isHorizontallyOverflowing =>
+      bodyContentSize.width > bodyViewport.width;
+
+  bool get isVerticallyOverflowing =>
+      bodyContentSize.height > bodyViewport.height;
+
+  @override
+  int get hashCode => Object.hash(bodyContentSize, bodyViewport);
+
+  const CategoryDayViewLayoutMetrics({
+    required this.bodyContentSize,
+    required this.bodyViewport,
+  });
+
+  @override
+  bool operator ==(Object other) =>
+      identical(this, other) ||
+      other is CategoryDayViewLayoutMetrics &&
+          other.bodyContentSize == bodyContentSize &&
+          other.bodyViewport == bodyViewport;
+
+  @override
+  String toString() => 'CategoryDayViewLayoutMetrics('
+      'bodyContentSize: $bodyContentSize, bodyViewport: $bodyViewport)';
+}
+
 abstract class GroupingStrategy<T> {
   ({List<EventGroup<T>> grouped, List<CategorizedDayEvent<T>> nonGrouped})
       groupEvents(List<CategorizedDayEvent<T>> events);
 }
 
 class NoGroupingStrategy<T> implements GroupingStrategy<T> {
   const NoGroupingStrategy();
+
   @override
   ({List<EventGroup<T>> grouped, List<CategorizedDayEvent<T>> nonGrouped})
       groupEvents(List<CategorizedDayEvent<T>> events) {
@@ -49,6 +84,7 @@ class EventGroup<T> extends CategorizedDayEvent<T> {
 
 abstract class GroupLayoutStrategy<T, U> {
   const GroupLayoutStrategy();
+
   bool canLayout(EventGroup<T> group) => true;
 
   Widget layout(
@@ -93,13 +129,19 @@ class CategoryOverflowCalendarDayView<T, U> extends StatefulWidget
     required this.minColumnWidth,
     required this.timeLabelsFormatter,
     required this.currentTimeFormatter,
+    this.horizontalScrollControllerGroup,
+    this.verticalScrollControllerGroup,
+    this.onLayoutMetrics,
     ValueGetter<DateTime>? clock,
   })  : clock = clock ?? DateTime.now,
         super(key: key);
 
   final Border? tableBodyBorder;
   final Border? timeColumnBorder;
   final double minColumnWidth;
+  final LinkedScrollControllerGroup? horizontalScrollControllerGroup;
+  final LinkedScrollControllerGroup? verticalScrollControllerGroup;
+  final CategoryDayViewLayoutMetricsCallback? onLayoutMetrics;
   final ValueGetter<DateTime> clock;
   final GroupingStrategy<T>? groupingStrategy;
   final GroupLayoutStrategy<T, U>? groupLayoutStrategy;
@@ -176,13 +218,34 @@ class CategoryOverflowCalendarDayView<T, U> extends StatefulWidget
 
 class _CategoryOverflowCalendarDayViewState<T, U>
     extends State<CategoryOverflowCalendarDayView<T, U>> {
-  final _horizontalScrollLink = LinkedScrollControllerGroup();
+  late final _horizontalScrollLink =
+      widget.horizontalScrollControllerGroup ?? LinkedScrollControllerGroup();
   late final _headerScrollController = _horizontalScrollLink.addAndGet();
   late final _horizScrollController = _horizontalScrollLink.addAndGet();
-  final _verticalScrollLink = LinkedScrollControllerGroup();
+  late final _verticalScrollLink =
+      widget.verticalScrollControllerGroup ?? LinkedScrollControllerGroup();
   late final _timeScrollController = _verticalScrollLink.addAndGet();
   late final _vertScrollController = _verticalScrollLink.addAndGet();
 
+  /// Identifies the scrollable body so its viewport rect can be measured.
+  final _bodyKey = GlobalKey();
+
+  /// Measures the scrollable body's viewport relative to the day view's
+  /// top-left, so the result accounts for the header and any safe-area inset.
+  /// Returns null while the render tree is not ready to be measured.
+  Rect? _measureBodyViewport() {
+    final root = context.findRenderObject();
+    final body = _bodyKey.currentContext?.findRenderObject();
+    if (root is! RenderBox ||
+        body is! RenderBox ||
+        !root.hasSize ||
+        !body.hasSize) {
+      return null;
+    }
+
+    return body.localToGlobal(Offset.zero, ancestor: root) & body.size;
+  }
+
   @override
   Widget build(BuildContext context) {
     final timeStart = widget.currentDate.copyTimeAndMinClean(widget.startOfDay);
@@ -207,6 +270,28 @@ class _CategoryOverflowCalendarDayViewState<T, U>
           final rowLength = totalWidth - widget.timeColumnWidth;
           final tileWidth = rowLength / categoriesCount;
 
+          final onLayoutMetrics = widget.onLayoutMetrics;
+
+          if (onLayoutMetrics != null) {
+            final bodyContentSize = Size(
+              rowLength,
+              rowHeight * timeList.length,
+            );
+
+            WidgetsBinding.instance.addPostFrameCallback((_) {
+              if (!mounted) return;
+
+              final bodyViewport = _measureBodyViewport();
+
+              if (bodyViewport == null) return;
+
+              onLayoutMetrics(CategoryDayViewLayoutMetrics(
+                bodyContentSize: bodyContentSize,
+                bodyViewport: bodyViewport,
+              ));
+            });
+          }
+
           return Column(
             mainAxisSize: MainAxisSize.min,
             children: [
@@ -261,6 +346,7 @@ class _CategoryOverflowCalendarDayViewState<T, U>
                     ),
                     Expanded(
                       child: ClipPath(
+                        key: _bodyKey,
                         clipper: VerticalClipper(),
                         child: DecoratedBox(
                           decoration: BoxDecoration(
@@ -314,6 +400,15 @@ class _CategoryOverflowCalendarDayViewState<T, U>
       ),
     );
   }
+
+  @override
+  void dispose() {
+    _headerScrollController.dispose();
+    _horizScrollController.dispose();
+    _timeScrollController.dispose();
+    _vertScrollController.dispose();
+    super.dispose();
+  }
 }
 
 class VerticalClipper extends CustomClipper<Path> {