blank

An invisible mark. blank takes up space and can be positioned and named like any other mark, but draws nothing. It is the positioning guide that line and ribbon trace.

from gofish import layer, chart, spread, blank, select_all, area

layer([
    chart(lake_totals)
        .flow(spread(by="lake", dir="x", spacing=64))
        .mark(blank(h="count").name("points")),
    chart(select_all("points")).mark(ribbon(opacity=0.8)),
]).render(w=500, h=300, axes=True)

Signature

blank(w=None, h=None, **options) -> Mark

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
em_x	bool		Embed x in the parent's x space.
em_y	bool		Embed y in the parent's y space.
w	int | float | str	0	Width.
h	int | float | str	0	Height.
fill	str		Fill color. A blank never paints; fill only seeds the shared color scale.
debug	bool		Dev-only flag: logs this mark's key and datum to the console as it is built. It changes nothing about what is drawn.

Returns a Mark for use in .mark().

Why use a blank?

A blank lets you run a full layout — spread, stack, scatter — and capture the positions without drawing anything. Name the result with .name(...), then have another chart select_all() it and draw a line, ribbon, or other mark through those positions.

# Position points, draw nothing — then connect them
chart(data).flow(scatter(by="lake", x="x", y="y")).mark(blank().name("points"))
chart(select_all("points")).mark(line())

Notes

• A blank still occupies layout space; its w/h participate in scales and positioning even though nothing is painted.