Visual primitive

Legend `has_legend`

Mini swatches mapping colours/markers to series names.

Required for any multi-series chart unless every series is labelled inline (e.g., end-of-line labels on a slope chart). Inline labels are usually preferable because the eye does not have to round-trip between chart and legend.

When critical

Multi-series charts where colours encode different categories: stacked/grouped bars, multi-line, multi-area, donut-multi, choropleth.

When optional

Single-series chart, or charts where every element is labelled inline.

Failures when missing

missing-label
the reader cannot tell which colour is which series

Failures when present (badly)

rainbow-palette + legend = headache (the colours are not memorable enough)
legend at the bottom for a tall narrow chart wastes space

Critical for families

composition
flow
correlation

Aspose property bindings

Legend.visibility
Legend.position