Negative `zoomOffset` in `TileLayer` causes crash

[ChibangLW]

What is the bug?

Great work on the library, thank you. Having a negative zoomOffset for a TileLayer crashes flutter_map in v8.2.0 and v8.2.1. It used to work with the previous version although an other caching setup.

ArgumentError: Invalid argument(s): -1
  #0      int._shlFromInteger (dart:core-patch/integers.dart:86:42)
  #1      int.<< (dart:core-patch/integers.dart:117:49)
  #2      TileCoordinatesResolver.get (package:flutter_map/src/layer/tile_layer/tile_coordinates.dart:83:22)
  #3      TileImageView._retainAncestor (package:flutter_map/src/layer/tile_layer/tile_image_view.dart:146:40)
  #4      TileImageView._retainAncestor (package:flutter_map/src/layer/tile_layer/tile_image_view.dart:157:14)
  #5      TileImageView.staleTiles (package:flutter_map/src/layer/tile_layer/tile_image_view.dart:73:32)
  #6      TileImageManager._prune (package:flutter_map/src/layer/tile_layer/tile_image_manager.dart:244:48)
  #7      TileImageManager.evictAndPrune (package:flutter_map/src/layer/tile_layer/tile_image_manager.dart:201:5)
  #8      _TileLayerState._loadAndPruneInVisibleBounds (package:flutter_map/src/layer/tile_layer/tile_layer.dart:690:23)
  #9      _TileLayerState.didChangeDependencies (package:flutter_map/src/layer/tile_layer/tile_layer.dart:459:22)
  #10      StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:5860:11)
  #11      ComponentElement.mount (package:flutter/src/widgets/framework.dart:5691:5)
  #12      Element.inflateWidget (package:flutter/src/widgets/framework.dart:4539:16)
  #13      MultiChildRenderObjectElement.inflateWidget (package:flutter/src/widgets/framework.dart:7159:36)
  #14      MultiChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:7175:32)
  #15      Element.inflateWidget (package:flutter/src/widgets/framework.dart:4539:16)
  #16      Element.updateChild (package:flutter/src/widgets/framework.dart:4004:18)
  #17      SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:7008:14)
  #18      Element.inflateWidget (package:flutter/src/widgets/framework.dart:4539:16)
  #19      Element.updateChild (package:flutter/src/widgets/framework.dart:3998:20)
  #20      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:5738:16)
  #21      Element.rebuild (package:flutter/src/widgets/framework.dart:5427:7)
  #22      ProxyElement.update (package:flutter/src/widgets/framework.dart:6041:5)
  #23      Element.updateChild (package:flutter/src/widgets/framework.dart:3982:15)
  #24      SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:7015:14)
  #25      Element.updateChild (package:flutter/src/widgets/framework.dart:3982:15)
  #26      SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:7015:14)
  #27      Element.updateChild (package:flutter/src/widgets/framework.dart:3982:15)
  #28      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:5738:16)
  #29      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5874:11)
  #30      Element.rebuild (package:flutter/src/widgets/framework.dart:5427:7)
  #31      StatefulElement.update (package:flutter/src/widgets/framework.dart:5899:5)
  #32      Element.updateChild (package:flutter/src/widgets/framework.dart:3982:15)
  #33      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:5738:16)
  #34      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5874:11)
  #35      Element.rebuild (package:flutter/src/widgets/framework.dart:5427:7)
  #36      StatefulElement.update (package:flutter/src/widgets/framework.dart:5899:5)
  #37      Element.updateChild (package:flutter/src/widgets/framework.dart:3982:15)
  #38      SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:7015:14)
  #39      Element.updateChild (package:flutter/src/widgets/framework.dart:3982:15)
  #40      SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:7015:14)
  #41      Element.updateChild (package:flutter/src/widgets/framework.dart:3982:15)
  #42      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:5738:16)
  #43      Element.rebuild (package:flutter/src/widgets/framework.dart:5427:7)
  #44      ProxyElement.update (package:flutter/src/widgets/framework.dart:6041:5)
  #45      _InheritedNotifierElement.update (package:flutter/src/widgets/inherited_notifier.dart:108:11)
  #46      Element.updateChild (package:flutter/src/widgets/framework.dart:3982:15)
  #47      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:5738:16)
  #48      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5874:11)
  #49      Element.rebuild (package:flutter/src/widgets/framework.dart:5427:7)
  #50      StatefulElement.update (package:flutter/src/widgets/framework.dart:5899:5)
  #51      Element.updateChild (package:flutter/src/widgets/framework.dart:3982:15)
  #52      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:5738:16)
  #53      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5874:11)
  #54      Element.rebuild (package:flutter/src/widgets/framework.dart:5427:7)
  #55      StatefulElement.update (package:flutter/src/widgets/framework.dart:5899:5)
  #56      Element.updateChild (package:flutter/src/widgets/framework.dart:3982:15)
  #57      _LayoutBuilderElement._rebuildWithConstraints.updateChildCallback (package:flutter/src/widgets/layout_builder.dart:249:18)
  #58      BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:3046:19)
  #59      _LayoutBuilderElement._rebuildWithConstraints (package:flutter/src/widgets/layout_builder.dart:272:12)
  #60      RenderAbstractLayoutBuilderMixin.layoutCallback (package:flutter/src/widgets/layout_builder.dart:335:38)
  #61      RenderObjectWithLayoutCallbackMixin.runLayoutCallback.<fn> (package:flutter/src/rendering/object.dart:4209:33)
  #62      RenderObject.invokeLayoutCallback.<fn> (package:flutter/src/rendering/object.dart:2941:17)
  #63      PipelineOwner._enableMutationsToDirtySubtrees (package:flutter/src/rendering/object.dart:1209:15)
  #64      RenderObject.invokeLayoutCallback (package:flutter/src/rendering/object.dart:2940:14)
  #65      RenderObjectWithLayoutCallbackMixin.runLayoutCallback (package:flutter/src/rendering/object.dart:4209:5)
  #66      _RenderLayoutBuilder.performLayout (package:flutter/src/widgets/layout_builder.dart:449:5)
  #67      RenderObject.layout (package:flutter/src/rendering/object.dart:2822:7)
  #68      RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:18)
  #69      RenderObject.layout (package:flutter/src/rendering/object.dart:2822:7)
  #70      ChildLayoutHelper.layoutChild (package:flutter/src/rendering/layout_helper.dart:62:11)
  #71      RenderStack._computeSize (package:flutter/src/rendering/stack.dart:646:43)
  #72      RenderStack.performLayout (package:flutter/src/rendering/stack.dart:673:12)
  #73      RenderObject.layout (package:flutter/src/rendering/object.dart:2822:7)
  #74      ChildLayoutHelper.layoutChild (package:flutter/src/rendering/layout_helper.dart:62:11)
  #75      RenderFlex._computeSizes (package:flutter/src/rendering/flex.dart:1202:26)
  #76      RenderFlex.performLayout (package:flutter/src/rendering/flex.dart:1255:32)
  #77      RenderObject.layout (package:flutter/src/rendering/object.dart:2822:7)
  #78      RenderPadding.performLayout (package:flutter/src/rendering/shifted_box.dart:243:12)
  #79      RenderObject.layout (package:flutter/src/rendering/object.dart:2822:7)
  #80      MultiChildLayoutDelegate.layoutChild (package:flutter/src/rendering/custom_layout.dart:180:12)
  #81      _ScaffoldLayout.performLayout (package:flutter/src/material/scaffold.dart:1118:7)
  #82      MultiChildLayoutDelegate._callPerformLayout (package:flutter/src/rendering/custom_layout.dart:249:7)
  #83      RenderCustomMultiChildLayoutBox.performLayout (package:flutter/src/rendering/custom_layout.dart:419:14)
  #84      RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:2655:7)
  #85      PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:1160:18)
  #86      PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:1173:15)
  #87      RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:629:23)
  #88      WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:1242:13)
  #89      RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:495:5)
  #90      SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1438:15)
  #91      SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1351:9)
  #92      SentryWidgetsBindingMixin.handleDrawFrame (package:sentry_flutter/src/binding_wrapper.dart:128:11)
  #93      SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:1204:5)
  #94      _invoke (dart:ui/hooks.dart:331:13)
  #95      PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:444:5)
  #96      _drawFrame (dart:ui/hooks.dart:303:31)

How can we reproduce it?

Causes flutter_map to crash:

TileLayer(
      zoomOffset: -5
      minNativeZoom: 5,
      maxNativeZoom: 18,
      urlTemplate: 'https://sgx.geodatenzentrum.de/wmts_basemapde/tile/1.0.0/de_basemapde_web_raster_grau/default/DE_EPSG_3857_ADV/{z}/{y}/{x}.png',
      tileProvider: NetworkTileProvider(
        cachingProvider:
            BuiltInMapCachingProvider.getOrCreateInstance(),
      ),
    )

Tile Documentation

Works correct:

TileLayer(
      minNativeZoom: 5,
      maxNativeZoom: 18,
      urlTemplate: 'https://sgx.geodatenzentrum.de/wmts_basemapde/tile/1.0.0/de_basemapde_web_raster_grau/default/GLOBAL_WEBMERCATOR/{z}/{y}/{x}.png',
      tileProvider: NetworkTileProvider(
        cachingProvider:
            BuiltInMapCachingProvider.getOrCreateInstance(),
      ),
    )

Do you have a potential solution?

No response

[JaffaKetchup]

Thanks for the report, we'll look into it! I don't think this is related to the caching functionality, likely another change, looking at the trace.

[JaffaKetchup]

This was introduced in #2060 whilst attempting to fix #2042.

I guess we didn't realise a negative offset could cause problems. @monsieurtanuki any ideas? Untested, but would it be correct just to absolute the zoom offset? Or adjust the condition above to be < zoomOffset?

flutter_map/lib/src/layer/tile_layer/tile_coordinates.dart

Lines 80 to 83 in 7d9dd32

	if (positionCoordinates.z < 0) {
	return positionCoordinates;
	}
	final modulo = 1 << (positionCoordinates.z + zoomOffset);

[monsieurtanuki]

@JaffaKetchup Very strange - dart wise - as:

ArgumentError: Invalid argument(s): -1
  #0      int._shlFromInteger (dart:core-patch/integers.dart:86:42)
  #1      int.<< (dart:core-patch/integers.dart:117:49)
  #2      TileCoordinatesResolver.get (package:flutter_map/src/layer/tile_layer/tile_coordinates.dart:83:22)

...happens after a test of positionCoordinates.z < 0 that should prevent the -1 value.

• would positionCoordinates change the value of z between the if and the <<?
• should we explicitly set a variable like final int z = positionCoordinates.z?

[JaffaKetchup]

But surely this will happen if zoomOffset is less than z? Even if z is >= 0?

[monsieurtanuki]

But surely this will happen if zoomOffset is less than z? Even if z is >= 0?

Oops, you're right.

The code used to be:

    if (positionCoordinates.z < 0) {
      return positionCoordinates;
    }
    final modulo = 1 << positionCoordinates.z;

Can't remember the exact purpose of zoomOffset, but I guess the fix would be something like that:

    if (positionCoordinates.z + zoomOffset < 0) {
      return positionCoordinates;
    }
    final modulo = 1 << (positionCoordinates.z + zoomOffset);

[EtzBetz]

Hey there!
I'm currently running into an issue with version 8.2.1, where having only one marker to fit to with a CameraFit.bounds() call, without maxZoom given, it will crash.
When giving a maxZoom or two markers (i guess with a sufficient offset needed), it wont crash anymore. so i guess when having only one marker for the CameraFit, it will try to zoom infinitely far in? In those crash cases lat,lng have been NaN and zoomlevel has been Infinity.

Maybe thats related to this as well? Or should I open another issue? If you need more information i can help.

[JaffaKetchup]

Hey @ChibangLW, this may be resolved on master. If you could test it out, that would be great!

---

Hi @EtzBetz, that sounds like a separate issue. If you could open a new issue with a little more info, that would be great!

[ChibangLW]

Thanks for the fast response. flutter_map doesn't crash anymore, but I can't display a map neigher when using the negative offset. I'm not sure what the problem is now. There seem to be no errors.

I'm using the linked tile server from the Federal Agency for Cartography and Geodesy of Germany. As stated on page 6 of the linked document, they use zoom levels with an offset for their Germany only local tiles.

Just as a note the tiles for good and bad in the initial issue differ by the actual tileset used (last part before zoom).

Is there anything I can support you with?

[EtzBetz]

Hi @EtzBetz, that sounds like a separate issue. If you could open a new issue with a little more info, that would be great!

I just did in #2135 :) I hope it helps