handle drag n drop

packages/z-timeline/lib/main.dart

@@ -83,6 +83,7 @@ class _MainAppState extends State<MainApp> {
             start: start,
             end: end,
             lane: item.lane,
+            hasEnd: item.end != null,
           ),
         );
       }
@@ -118,16 +119,21 @@ class _MainAppState extends State<MainApp> {
     String newGroupId,
     int newLane,
   ) {
-    final duration = entry.end.difference(entry.start);
-    final newEnd = newStart.add(duration);
-
-    emitEvent('entry_moved', {
+    final payload = <String, Object?>{
       'entryId': entry.id,
       'newStart': newStart.toIso8601String(),
-      'newEnd': newEnd.toIso8601String(),
       'newGroupId': newGroupId,
       'newLane': newLane,
-    });
+    };
+
+    if (entry.hasEnd) {
+      final duration = entry.end.difference(entry.start);
+      payload['newEnd'] = newStart.add(duration).toIso8601String();
+    } else {
+      payload['newEnd'] = null;
+    }
+
+    emitEvent('entry_moved', payload);
   }
 
   void _emitContentHeight() {

packages/z-timeline/lib/src/models/timeline_entry.dart

@@ -8,6 +8,7 @@ class TimelineEntry {
     required this.start,
     required this.end,
     required this.lane,
+    this.hasEnd = true,
   }) : assert(!end.isBefore(start), 'Entry end must be on/after start');
 
   final String id;
@@ -15,6 +16,7 @@ class TimelineEntry {
   final DateTime start;
   final DateTime end;
   final int lane; // provided by consumer for stacking
+  final bool hasEnd; // false for point-events (end is synthetic)
 
   bool overlaps(DateTime a, DateTime b) {
     return !(end.isBefore(a) || start.isAfter(b));
@@ -26,6 +28,7 @@ class TimelineEntry {
     DateTime? start,
     DateTime? end,
     int? lane,
+    bool? hasEnd,
   }) {
     return TimelineEntry(
       id: id ?? this.id,
@@ -33,11 +36,12 @@ class TimelineEntry {
       start: start ?? this.start,
       end: end ?? this.end,
       lane: lane ?? this.lane,
+      hasEnd: hasEnd ?? this.hasEnd,
     );
   }
 
   @override
-  int get hashCode => Object.hash(id, groupId, start, end, lane);
+  int get hashCode => Object.hash(id, groupId, start, end, lane, hasEnd);
 
   @override
   bool operator ==(Object other) {
@@ -46,10 +50,11 @@ class TimelineEntry {
         other.groupId == groupId &&
         other.start == start &&
         other.end == end &&
-        other.lane == lane;
+        other.lane == lane &&
+        other.hasEnd == hasEnd;
   }
 
   @override
   String toString() =>
-      'TimelineEntry(id: $id, groupId: $groupId, start: $start, end: $end, lane: $lane)';
+      'TimelineEntry(id: $id, groupId: $groupId, start: $start, end: $end, lane: $lane, hasEnd: $hasEnd)';
 }