Feature layer hit testing throws `LateInitializationError` in some cases

[corepuncher]

What is the bug?

Maybe FM 8.1.0 related?

I can reproduce easily by simply toggling off layers (removing things like polygons or lines widgets).

When this happens, the map no longer responds, and it just continually throws exceptions

I reverted back to 8.0.0, and the issue went away.

It appears that in some cases the code path for hit testing (for instance in _PolygonPainter.elementHitTest) is triggering the access of _viewportRect without ensuring it’s initialized.

════════ Exception caught by gestures library ═════════
The following LateError was thrown while handling a pointer data packet:
LateInitializationError: Field '_viewportRect@1639329998' has not been initialized.

When the exception was thrown, this was the stack:
#0      FeatureLayerUtils.viewportRect (package:flutter_map/src/layer/shared/feature_layer_utils.dart:16:28)
feature_layer_utils.dart:16
#1      FeatureLayerUtils.areOffsetsVisible (package:flutter_map/src/layer/shared/feature_layer_utils.dart:40:11)
feature_layer_utils.dart:40
#2      _PolygonPainter.elementHitTest.checkIfHit (package:flutter_map/src/layer/polygon_layer/painter.dart:75:12)
painter.dart:75
#3      FeatureLayerUtils.workAcrossWorlds (package:flutter_map/src/layer/shared/feature_layer_utils.dart:58:13)
feature_layer_utils.dart:58
#4      _PolygonPainter.elementHitTest (package:flutter_map/src/layer/polygon_layer/painter.dart:112:12)
painter.dart:112
#5      HitDetectablePainter.hitTest (package:flutter_map/src/layer/shared/layer_interactivity/internal_hit_detectable.dart:69:11)
internal_hit_detectable.dart:69
#6      RenderCustomPaint.hitTestSelf (package:flutter/src/rendering/custom_paint.dart:569:43)
custom_paint.dart:569
#7      RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:58)
box.dart:2943
#8      RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#9      RenderTransform.hitTestChildren.<anonymous closure> (package:flutter/src/rendering/proxy_box.dart:2560:22)
proxy_box.dart:2560
#10     BoxHitTestResult.addWithRawTransform (package:flutter/src/rendering/box.dart:876:31)
box.dart:876
#11     BoxHitTestResult.addWithPaintTransform (package:flutter/src/rendering/box.dart:810:12)
box.dart:810
#12     RenderTransform.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:2556:19)
proxy_box.dart:2556
#13     RenderTransform.hitTest (package:flutter/src/rendering/proxy_box.dart:2550:12)
proxy_box.dart:2550
#14     RenderShiftedBox.hitTestChildren.<anonymous closure> (package:flutter/src/rendering/shifted_box.dart:95:24)
shifted_box.dart:95
#15     BoxHitTestResult.addWithPaintOffset (package:flutter/src/rendering/box.dart:840:31)
box.dart:840
#16     RenderShiftedBox.hitTestChildren (package:flutter/src/rendering/shifted_box.dart:90:21)
shifted_box.dart:90
#17     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#18     RenderBoxContainerDefaultsMixin.defaultHitTestChildren.<anonymous closure> (package:flutter/src/rendering/box.dart:3339:25)
box.dart:3339
#19     BoxHitTestResult.addWithPaintOffset (package:flutter/src/rendering/box.dart:840:31)
box.dart:840
#20     RenderBoxContainerDefaultsMixin.defaultHitTestChildren (package:flutter/src/rendering/box.dart:3334:33)
box.dart:3334
#21     RenderStack.hitTestChildren (package:flutter/src/rendering/stack.dart:695:12)
stack.dart:695
#22     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#23     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#24     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#25     RenderBoxContainerDefaultsMixin.defaultHitTestChildren.<anonymous closure> (package:flutter/src/rendering/box.dart:3339:25)
box.dart:3339
#26     BoxHitTestResult.addWithPaintOffset (package:flutter/src/rendering/box.dart:840:31)
box.dart:840
#27     RenderBoxContainerDefaultsMixin.defaultHitTestChildren (package:flutter/src/rendering/box.dart:3334:33)
box.dart:3334
#28     RenderStack.hitTestChildren (package:flutter/src/rendering/stack.dart:695:12)
stack.dart:695
#29     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#30     RenderBoxContainerDefaultsMixin.defaultHitTestChildren.<anonymous closure> (package:flutter/src/rendering/box.dart:3339:25)
box.dart:3339
#31     BoxHitTestResult.addWithPaintOffset (package:flutter/src/rendering/box.dart:840:31)
box.dart:840
#32     RenderBoxContainerDefaultsMixin.defaultHitTestChildren (package:flutter/src/rendering/box.dart:3334:33)
box.dart:3334
#33     RenderStack.hitTestChildren (package:flutter/src/rendering/stack.dart:695:12)
stack.dart:695
#34     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#35     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#36     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#37     RenderClipRect.hitTest (package:flutter/src/rendering/proxy_box.dart:1568:18)
proxy_box.dart:1568
#38     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#39     RenderProxyBoxWithHitTestBehavior.hitTest (package:flutter/src/rendering/proxy_box.dart:183:19)
proxy_box.dart:183
#40     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#41     RenderProxyBoxWithHitTestBehavior.hitTest (package:flutter/src/rendering/proxy_box.dart:183:19)
proxy_box.dart:183
#42     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#43     RenderProxyBoxWithHitTestBehavior.hitTest (package:flutter/src/rendering/proxy_box.dart:183:19)
proxy_box.dart:183
#44     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#45     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#46     _RenderLayoutBuilder.hitTestChildren (package:flutter/src/widgets/layout_builder.dart:407:19)
layout_builder.dart:407
#47     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#48     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#49     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#50     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#51     RenderProxyBoxWithHitTestBehavior.hitTest (package:flutter/src/rendering/proxy_box.dart:183:19)
proxy_box.dart:183
#52     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#53     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#54     RenderBoxContainerDefaultsMixin.defaultHitTestChildren.<anonymous closure> (package:flutter/src/rendering/box.dart:3339:25)
box.dart:3339
#55     BoxHitTestResult.addWithPaintOffset (package:flutter/src/rendering/box.dart:840:31)
box.dart:840
#56     RenderBoxContainerDefaultsMixin.defaultHitTestChildren (package:flutter/src/rendering/box.dart:3334:33)
box.dart:3334
#57     RenderStack.hitTestChildren (package:flutter/src/rendering/stack.dart:695:12)
stack.dart:695
#58     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#59     RenderBoxContainerDefaultsMixin.defaultHitTestChildren.<anonymous closure> (package:flutter/src/rendering/box.dart:3339:25)
box.dart:3339
#60     BoxHitTestResult.addWithPaintOffset (package:flutter/src/rendering/box.dart:840:31)
box.dart:840
#61     RenderBoxContainerDefaultsMixin.defaultHitTestChildren (package:flutter/src/rendering/box.dart:3334:33)
box.dart:3334
#62     RenderCustomMultiChildLayoutBox.hitTestChildren (package:flutter/src/rendering/custom_layout.dart:429:12)
custom_layout.dart:429
#63     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#64     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#65     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#66     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#67     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#68     RenderPhysicalModel.hitTest (package:flutter/src/rendering/proxy_box.dart:2032:18)
proxy_box.dart:2032
#69     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#70     RenderProxyBoxWithHitTestBehavior.hitTest (package:flutter/src/rendering/proxy_box.dart:183:19)
proxy_box.dart:183
#71     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#72     RenderProxyBoxWithHitTestBehavior.hitTest (package:flutter/src/rendering/proxy_box.dart:183:19)
proxy_box.dart:183
#73     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#74     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#75     _RenderLayoutBuilder.hitTestChildren (package:flutter/src/widgets/layout_builder.dart:407:19)
layout_builder.dart:407
#76     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#77     RenderBoxContainerDefaultsMixin.defaultHitTestChildren.<anonymous closure> (package:flutter/src/rendering/box.dart:3339:25)
box.dart:3339
#78     BoxHitTestResult.addWithPaintOffset (package:flutter/src/rendering/box.dart:840:31)
box.dart:840
#79     RenderBoxContainerDefaultsMixin.defaultHitTestChildren (package:flutter/src/rendering/box.dart:3334:33)
box.dart:3334
#80     RenderStack.hitTestChildren (package:flutter/src/rendering/stack.dart:695:12)
stack.dart:695
#81     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#82     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#83     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#84     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#85     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#86     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#87     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#88     RenderIgnorePointer.hitTest (package:flutter/src/rendering/proxy_box.dart:3625:31)
proxy_box.dart:3625
#89     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#90     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#91     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#92     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#93     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#94     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#95     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#96     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#97     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#98     RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#99     RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#100    RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#101    RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#102    RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#103    RenderOffstage.hitTest (package:flutter/src/rendering/proxy_box.dart:3756:31)
proxy_box.dart:3756
#104    RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#105    RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#106    _RenderTheaterMixin.hitTestChildren.childHitTest (package:flutter/src/widgets/overlay.dart:1097:22)
overlay.dart:1097
#107    BoxHitTestResult.addWithPaintOffset (package:flutter/src/rendering/box.dart:840:31)
box.dart:840
#108    _RenderTheaterMixin.hitTestChildren (package:flutter/src/widgets/overlay.dart:1098:22)
overlay.dart:1098
#109    RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#110    RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#111    RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#112    RenderAbsorbPointer.hitTest (package:flutter/src/rendering/proxy_box.dart:3877:56)
proxy_box.dart:3877
#113    RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#114    RenderProxyBoxWithHitTestBehavior.hitTest (package:flutter/src/rendering/proxy_box.dart:183:19)
proxy_box.dart:183
#115    RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#116    RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#117    RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#118    RenderCustomPaint.hitTestChildren (package:flutter/src/rendering/custom_paint.dart:564:18)
custom_paint.dart:564
#119    RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#120    RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#121    RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#122    RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#123    RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#124    RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#125    RenderTapRegionSurface.hitTest (package:flutter/src/widgets/tap_region.dart:234:28)
tap_region.dart:234
#126    RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#127    RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#128    RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#129    RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#130    RenderProxyBoxMixin.hitTestChildren (package:flutter/src/rendering/proxy_box.dart:128:19)
proxy_box.dart:128
#131    RenderBox.hitTest (package:flutter/src/rendering/box.dart:2943:11)
box.dart:2943
#132    RenderView.hitTest (package:flutter/src/rendering/view.dart:311:12)
view.dart:311
#133    RendererBinding.hitTestInView (package:flutter/src/rendering/binding.dart:649:34)
binding.dart:649
#134    GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:408:7)
binding.dart:408
#135    GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:394:5)
binding.dart:394
#136    GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:341:7)
binding.dart:341
#137    GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:308:9)
binding.dart:308
#138    _invoke1 (dart:ui/hooks.dart:332:13)
hooks.dart:332
#139    PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:451:7)
platform_dispatcher.dart:451
#140    _dispatchPointerDataPacket (dart:ui/hooks.dart:267:31)
hooks.dart:267

How can we reproduce it?

For me, just toggling various polygon layers off causes the exceptions immediately.

Do you have a potential solution?

No response

[monsieurtanuki]

@corepuncher Thanks to your clear description, that should be easy to fix.
Something like

  /// The rectangle of the canvas on its last paint
  ///
  /// Must not be retrieved before [paint] has been called.
  Rect? get viewportRect => _viewportRect;
  Rect? _viewportRect;

  @mustCallSuper
  @mustBeOverridden
  @override
  void paint(Canvas canvas, Size size) {
    _viewportRect = Offset.zero & size;
  }

in feature_layer_utils.dart, and small null tests here and there.

[JaffaKetchup]

@corepuncher Can you provide a small sample of code and how you 'toggle it off'? I'm struggling to understand how the issue could happen - from my understanding, this would mean a hit is tested before a paint call is run. I'm probably missing something, but I just want to make sure I fully understand the root cause before applying the fix above.

[corepuncher]

For example, with a button that toggles showPolygons:

FlutterMap(
...
children: [
...
if (showPolygons)
    Opacity(
      opacity: someVar
          ? 1.0
          : 0.0,
      child: Consumer<ABC>(
        builder: (context, abc, child) {
          return Stack(
            children: [
              PolygonLayer(
                  key: ValueKey('somekey'),
                  simplificationTolerance: 0.3,
                  polygons: abc.linesAtFrame(frameIndex)),
              if (showLabels && mapState.zoom >= 6)
                MarkerLayer(
                  key: ValueKey(
                      'somekey'),
                  markers: abc.getMarkersAtFrame(frameIndex),
                ),
            ],
          );
        },
      ),
    ),
...others...
],
),

That's fairly typical, I have several data layers, and toggle buttons for each. This is the first time there has been an issue.

EDIT: Getting more specifc info, please hold.

[corepuncher]

More tests:

1. If I start in a part of the map where the Polygons are not visible, there is no issue. I can toggle on and off, and still pan.
2. Now if I pan to a part of the map where the polygons exist, then toggle them off, it freezes.
3. BUT THEN, if I toggle them back ON, the map UNFREEZES.

Then if I turn it off again it freezes, and so on.

Testing reveals a mouse issue (also not present with 8.0.0). Seems as though the mouse goes out coincident with the freezing/coming back issue. And if the map freezes (after toggling the polygons off), and I toggle them back on (thereby re-enabled map gestures), while finger gestures seem to all work, mouse panning stops working, but wheel zoom works.

Exception caught by gestures library
'package:flutter/src/rendering/mouse_tracker.dart': Failed assertion: line 203 pos 12: '!_debugDuringDeviceUpdate': is not true.

[corepuncher]

Another reveal...
Only THAT particular PolygonLayer has the issue. Similar ones, such as below, do not:

in FM:

children: [
...
if (showXyx)
Visibility(
key: ValueKey('wvisibility'),
visible: various conditions,
child: Consumer(
builder: (context, xyz, child) {
return PolygonLayer(
key: ValueKey('XYZPolygon'),
simplificationTolerance: settings.xyzSimplification,
polygons: xyz.polygonsAtFrame(i));
},
),
),
...

Nothing too special about any of these widgets IMO.

Let me know if you need any more specific tests performed.

[JaffaKetchup]

Thanks for the info, I'll look into it in the coming days!

[JaffaKetchup]

I think an MRE would be useful for this if you still have the issue and if you have the time! Seems fairly complicated and hard to reproduce, so there's probably some sort of edge case we're not covering. I'm also not sure at all, but I wonder if the keys might be involved?

[corepuncher]

I think an MRE would be useful for this if you still have the issue and if you have the time! Seems fairly complicated and hard to reproduce, so there's probably some sort of edge case we're not covering. I'm also not sure at all, but I wonder if the keys might be involved?

I will eventually do more testing on this. I really need to make a slimmed down version of this code for making MREs. I am going to try and get this app out to the world using 8.0.0. Then I'll take this one on.

Just be on the lookout. Will be interesting to see if someone else sees this behavior.

[JaffaKetchup]

Thanks for the info so far, but unfortunately without any other confirmed reproductions, I'm going to have to close this for now. It's entirely possible I've missed something, so please let me know if you find anything :)