Add options for toggling buildings, traffic, POIs in Mapbox Streets–sourced styles

[1ec5]

MGLStyle should have showsBuildings, showsTraffic, and showsPointsOfInterest properties that toggle the visibility of relevant layers in any style that uses the Mapbox Streets and/or Mapbox Traffic sources. These properties would help us achieve parity with the similarly named MKMapView properties in MapKit and the GMSMapView.buildingsEnabled and GMSMapView.trafficEnabled properties in the Google Maps SDK for iOS.

• showsBuildings would toggle the visibility of any MGLFillStyleLayer or MGLFillExtrusionStyleLayer whose source’s URL is mapbox.mapbox-streets-v7 and whose sourceLayerIdentifier is building.
• showsTraffic would toggle the visibility of any MGLLineStyleLayer whose source’s URL is mapbox://mapbox.mapbox-traffic-v1.
• showsPointsOfInterest would toggle the visibility of any MGLSymbolStyleLayer whose source’s URL is mapbox.mapbox-streets-v7 and whose sourceLayerIdentifier is poi_label.

We should also add corresponding IBInspectable properties to the MGLMapView(IBAdditions) category for parity with MapKit:

This feature would obviate mapbox/ios-sdk-examples#64.

/cc @bsudekum @frederoni @pveugen

[1ec5]

One thorny issue is what the getter’s default value should be and what the getter and setter should do in the event of a mixed state (some relevant layers shown, some hidden).

[1ec5]

#11726 proposes a similar inspectable for label localization.

[1ec5]

One thorny issue is what the getter’s default value should be and what the getter and setter should do in the event of a mixed state (some relevant layers shown, some hidden).

For the inspectable specifically, Interface Builder represents a Boolean property as a three-way option, with “Default Value” corresponding to the natural state where the setter is never called. So the question of a default value is only thorny for the public property but not the inspectable.

The public property could have a non-Boolean type, like MapKit’s three-way MKFeatureVisibility enumeration.

[fabian-guerra]

@1ec5 the traffic style is enabled by default. If someone uses:
mapbox://styles/mapbox/traffic-day-v2 will get the the traffic status turned on.

I'm not sure this IBInspectable would be necessary at all. Unless when setting the property on I reload with the traffic style, which it may be problematic for developers.

Or maybe just left it as a convenience method for navigation.

[1ec5]

It’s important to distinguish between the Traffic source and the Traffic Day/Night styles. As seen in the Traffic plugin, any style can have traffic congestion lines powered by the Traffic source; no reloading is required.

We could treat these inspectables as a way to force certain things on or off. When an inspectable is in its default state, we would leave the style untouched, so the Traffic Day style would have traffic by default, but the Streets style would not. On the other hand, when the inspectable is on, both styles would have traffic layers.

That said, some of these options, including traffic, could be problematic because we don’t necessarily know what would look good atop an arbitrary style. So we could scope down this feature even further: the inspectables would only hide certain layers but not create any layers on its own.

[stale]

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