format and fix

packages/z-timeline/lib/main.dart

@@ -59,6 +59,8 @@ class _MainAppState extends State<MainApp> {
         end: domain.end,
       );
     });
+
+    _emitContentHeight();
   }
 
   List<TimelineGroup> _convertGroups(List<TimelineGroupData> groups) {
@@ -168,6 +170,25 @@ class _MainAppState extends State<MainApp> {
             e,
       ];
     });
+
+    _emitContentHeight();
+  }
+
+  void _emitContentHeight() {
+    var totalHeight = 0.0;
+    for (final group in _groups) {
+      totalHeight += ZTimelineConstants.groupHeaderHeight;
+      final groupEntries = _entries.where((e) => e.groupId == group.id);
+      var maxLane = 0;
+      for (final e in groupEntries) {
+        if (e.lane > maxLane) maxLane = e.lane;
+      }
+      final lanesCount = maxLane.clamp(0, 1000);
+      totalHeight += lanesCount * ZTimelineConstants.laneHeight
+          + (lanesCount > 0 ? (lanesCount - 1) * ZTimelineConstants.laneVerticalSpacing : 0)
+          + ZTimelineConstants.verticalOuterPadding * 2;
+    }
+    emitEvent('content_height', {'height': totalHeight});
   }
 
   String _labelForEntry(TimelineEntry entry) {