Capability: Apply custom styling to map markers and vector features

[prushforth]

This issue is for discussion of the map viewer capability "Apply custom styling to map markers and vector features".

---

It's important that map authors be able to share the standards of the Web, without necessary extensions and pre-processors. The CSS model of styling should be used for styling map content.

[AmeliaBR]

I think this might end up being multiple sections, because there are many parts of the map that an author might want to style:

• buttons and other controls
• text labels
• route lines and areas
• marker points

[AmeliaBR]

I've got this issue now cross-referenced for discussion specifically of styling map markers and vector features (map content), with a separate capability for controls.