Some arbitrary HTML content, specified by the option TextContent (a Hypertext object or other content to render in HTML).
Due to a limitation of <foreignObject>, coordinates are rounded to the nearest integer. So use large enough coordinate systems.
The object GraphicsHtml is an instance of the type GraphicsType, with ancestor classes GraphicsText < GraphicsObject < GraphicsAncestor < HashTable < Thing.
The source of this document is in /build/reproducible-path/macaulay2-1.25.06+ds/M2/Macaulay2/packages/VectorGraphics.m2:1875:0.