For AI agents: a documentation index is available at /llms.txt. Markdown versions of all pages are available by appending .md to any URL.
ON_DATA_UPDATE_START
@SerialName(value = "dataloading")
Triggered when any map data (style, source, tile, etc) begins loading or changing asynchronously. All dataloading events are followed by a dataDidUpdate, dataUpdateDidAbort or error events.