UserLocation minDisplacement not limiting calls for onUpdate

Description of the issue/bug UserLocation.minDisplacement does not seem to limit the number of calls on UserLocation.onUpdate.

There is currently no documentation available, but I assume that the purpose of the property minDisplacement is to set the minimum distance (meters?) a user’s location has to change before UserLocation will receive an update.

Setting minDisplacement to high values did not make any difference though. UserLocation.onUpdate was called by rotating my phone without moving anywhere.

import React from 'react';
import {
  MapView,
  ShapeSource,
  LineLayer,
  Camera,
UserLocation,
} from '@react-native-mapbox-gl/maps';

const aLine = {
  type: 'LineString',
  coordinates: [
    [-74.00597, 40.71427],
    [-74.00697, 40.71527],
  ],
};

class BugReportExample extends React.Component {
  onUpdatePosition(location) {
    console.log('Updated position')
    // minDisplacement on UserLocation doesn't seem to limit the 
    // call for onUpdate. 
    this.setState({ location: location });
  }
  render() {
    return (
      <MapView style={{flex: 1}}>
        <Camera centerCoordinate={[-74.00597, 40.71427]} zoomLevel={14} />
        <ShapeSource id="idStreetLayer" shape={aLine}>
          <LineLayer id="idStreetLayer" />
        </ShapeSource>
          <UserLocation
            visible={true}
            renderMode={'normal'}
            minDisplacement={5}
            onUpdate={(location) => this.onUpdatePosition(location)}
            showsUserHeadingIndicator={true} />
      </MapView>
    );
  }
}

This might also be related to issue #770

I might just misunderstand the purpose of minDisplacement. If so then this would be a great feature to have.

Versions:

• Platform: iOS
• Device: iPhone11
• Emulator/ Simulator: no
• OS: 13.4.1
• react-native-mapbox-gl Version 8.0.0
• React Native Version 0.62.2

[mzu]

Hi @ferdicus. Just tested the branch and onUpdate gets now called as expected, i.e. when minDisplacement is reached. Thanks for taking care of this!

I just wanted to note that when showsUserHeadingIndicator={true} is set, the indicator arrow is also affected. It only updates along with minDisplacement. I assume it’s not possible with this fix to keep the onUpdate callback independent from the heading indicator updates. I just think that most use cases want to see the heading indicator continuously updating and see the displacement updates only in terms of ‘moving a certain distance on the ground’. Maybe the only solution for this case is to keep the displacement at 0 and limit any state updates inside the onUpdate callback instead.

At least there is now a choice since before the minDisplacement value didn’t have any effect on iOS. Thanks 😃

[mfazekas]

The userLocation expects heading for displaying direction. Maybe we can skip calling delegate when minDisplacement is set.