blank

Creates invisible positioning guides. Use blank when you need to define positions for other marks (like line or ribbon) without rendering visible shapes.

A blank draws nothing at all: it takes part in layout, carries its datum, can be named and selected with selectAll, and feeds the color scale, but it produces no SVG element and no hover target. That is unconditional — there is no option that makes a blank paint.

const locations = Object.entries(lakeLocations).map(([lake, { x, y }]) => ({
  lake,
  x,
  y,
}));

gf.layer([
  gf
    .chart(locations)
    .flow(gf.scatter({ by: "lake", x: "x", y: "y" }))
    .mark(gf.blank().name("points")),
  gf
    .chart(gf.selectAll("points"))
    .mark(gf.line({ stroke: "steelblue", strokeWidth: 2 })),
]).render(root, { w: 400, h: 250, axes: true });

Signature

blank({ w?, h?, fill?, debug? })

Parameters

An invisible sizing/positioning guide — a rect that emits no display items at all, with a restricted channel set (no x/y/cx/cy/x2/y2/theta/r — position it via a layout operator).

Option	Type	Default	Description
emX	boolean		Embed x in the parent's x space.
emY	boolean		Embed y in the parent's y space.
w	number | string | FieldExpr	0	Width.
h	number | string | FieldExpr	0	Height.
fill	string | FieldExpr		Fill color. A blank never paints; fill only seeds the shared color scale.
debug	boolean		Dev-only flag: logs this mark's key and datum to the console as it is built. It changes nothing about what is drawn.

Examples

// Create invisible anchor points for a line chart
.mark(blank().name("points"))

// Blank with height encoding for area charts
.mark(blank({ h: "value" }).name("bars"))

// Log each blank's key and datum to the console (it still draws nothing)
.mark(blank({ debug: true }).name("guides"))