Conflict between projection sources (style vs prop)

[SkySails]

Recently, with the introduction of #2294, we are now allowed to use the projection prop to set the projection used by the SDK.

However, I just realized that projection is part of the style spec. This means that we have to decide what has a higher priority - the projection prop or the style property. If I set globe inside my app and the style specifies projection: "mercator", what result should I expect?

Currently, as I've just realized, the behavior isn't even completely uniform between platforms. Both IOS and Android will initially force the projection set inside the projection prop, but switching styles is another story.

Current situation

On Android, we force the projection from the prop value every time a new style is loaded (reference). Since the projection defaults to mercator , any projection set in the file will be overridden on this platform.

The same cannot be said for IOS, where the projection is only set on prop changes and on initial load (reference). The state is not persisted, and if a new style with a different projection is loaded, it will change.

Opinion

I think that the prop should have a higher priority than the style property. However, we should probably make sure that - as long as no projection prop is set - we use fallback values in this order:

• projection prop
• projection style property
• SDK default (mercator)

Any thoughs? Sorry for not bringing this up before the merge - I just realized this.