A mark's facet containers, or none when the mark is not faceted.
Plot nests each facet's elements in a translated <g>, so a mark is faceted
when every child is a group; a mixed set means the groups are part of the
mark itself — an axis tick's line and label, say — rather than facet
containers.
Three separate readings turn on that distinction: what a mark's leaf elements
are, how it splits into facets, and where Plot wrote the styling that says a
tick is a box plot's median (#1074). They have to agree, so the rule lives
here rather than being spelled out at each of them.
Parameters
group: Element
A mark group.
Returns Element[]
The facet groups, or an empty array when the mark has none.
A mark's facet containers, or none when the mark is not faceted.
Plot nests each facet's elements in a translated
<g>, so a mark is faceted when every child is a group; a mixed set means the groups are part of the mark itself — an axis tick's line and label, say — rather than facet containers.Three separate readings turn on that distinction: what a mark's leaf elements are, how it splits into facets, and where Plot wrote the styling that says a
tickis a box plot's median (#1074). They have to agree, so the rule lives here rather than being spelled out at each of them.