Mapbox-gl-native: expose more style properties for annotations

[incanus]

Shape annotations need to support more features in the exposed API.

Definite:

• line join
• line cap
• line dash

Maybe:

• line/fill image
• translate (for putting lines next to roads? e.g. multiple transit line colors)
• antialias off?

@friedbunny

[friedbunny]

"Line/fill image" could also be useful for specifying symbols, like arrows. CartoCSS supported this via marker-type: arrow.

Line stroke would also be nice to have.

[jfirebaugh]

Can we expose exactly the set of properties that are in the style spec?

[incanus]

Can we expose exactly the set of properties that are in the style spec?

In C++, sure. We shouldn't do this all the way up in iOS because it would just crap up the delegate protocol, since that's where we configure these things (on a per-annotation basis).

[incanus]

Line stroke would also be nice to have.

BTW, this is in there for polylines already. For polygons, see https://github.com/mapbox/mapbox-gl-native/issues/1737 for why we can't do this right now.

[friedbunny]

@incanus I suppose I mean "stroke" in the Photoshop sense — an external casing around the filled line. Right now this requires duplicating the line and widening it, unless I'm missing something.

[incanus]

De-prioritizing this in light of https://github.com/mapbox/mapbox-gl-native/pull/1839, which solves the immediate problem at hand.

[webventil]

What about different colors or each shape point? Than there might be the possibility to make color gradients between each point to have something like heat maps for graphs.

[incanus]

@webventil Interesting idea, but not yet supported in the renderer, let alone exposed. Mind opening a new ticket for the feature so we can track?

[webventil]

I created a new issue for it (#2142).

[jfirebaugh]

Updating title to reflect that this is not specific to shape annotations -- markers could also benefit from style properties like icon-size and icon-rotate.

[ljbade]

This ticket is superseeded by https://github.com/mapbox/mapbox-gl-native/issues/837 which will allow the full range of style properties.

[incanus]

@jfirebaugh Should we close this in favor of #837 then?

[1ec5]

Reopening: the runtime styling API (#837, #5626) has landed on iOS and macOS, but something directly compatible with the existing annotation API would be a boon for developers who have to use that API for various reasons.

Per https://github.com/mapbox/mapbox-gl-native/issues/6172#issuecomment-242769482, support for additional annotation properties is mainly a matter of plumbing through style properties that can be applied to the symbol, line, or fill layer that the annotation adds to the style. We want to avoid a proliferation of methods on MGLMapViewDelegate; at the same time, MapKit’s MKOverlayRenderer class hierarchy may be a poor fit for our annotation implementation. Instead, we could introduce the idea of a _prototype style layer_: a single method on MGLMapViewDelegate, -mapView:prototypeStyleLayerForAnnotation: that returns an MGLStyleLayer object. The SDK would extract the underlying mbgl::style::Layer object and use it in mbgl::LineAnnotationImpl::updateStyle().

[jfirebaugh]

Re-closing; I feel strongly that we should focus our limited resources on the runtime styling API.