GoFish Graphics
Internals

connect ​

Draws a connector through the chart's own marks. .connect(line()) is builder sugar for the two-layer selectAll recipe: it positions the chart's marks, then threads a line or area through exactly those nodes, painted underneath.

python
from gofish import chart, scatter, circle, line

chart(driving_shifts, axes=True).flow(
    scatter(by="year", x="miles", y="gas")
).mark(circle(r=4, fill="white", stroke="black", strokeWidth=2)).connect(
    line(stroke="black", strokeWidth=2)
).render(w=500, h=300)

Signature ​

python
ChartBuilder.connect(mark) -> ChartBuilder

Parameters ​

ParameterTypeDescription
markMarkA ref-consuming mark — typically line() or area()

Returns a new ChartBuilder with the connector set.

Desugaring ​

.connect() is exactly the manual two-layer form. This:

python
chart(data, axes=True).flow(
    scatter(by="lake", x="x", y="y")
).mark(circle()).connect(line())

desugars to:

python
Layer([
    chart(data).flow(scatter(by="lake", x="x", y="y")).mark(circle().name("pts")),
    chart(selectAll("pts")).mark(line()).zOrder(-1),
])

The elaboration happens at resolve time (like axes and legends), so the sugar keeps the IR small and never leaks an extra layer into your code.

Semantics ​

  • Targets are exactly the nodes the chart's final mark registers — one per flow leaf, identical to what selectAll(name) yields in the manual form.
  • Name — if the mark carries a string .name("pts"), that name is used (and stays selectable by other charts). Otherwise no name is created at all: the chart tags its mark's nodes directly at resolve time, so nothing is minted, leaked, or serialized.
  • Paint order — the connector renders under the marks (the elaboration applies zOrder(-1) to the connector layer). This is fixed; reach for the manual Layer([...]) form if you need a different paint order.
  • Connector type — any ref-consuming mark works: line(), area().

Constraints ​

  • One call max. A second .connect() raises ValueError.
  • String names only. A non-string mark name raises TypeError.
  • Cross-chart connection — to connect another chart's marks, use the explicit Layer([...]) + selectAll form. .connect() only threads a chart through its own marks.