Motivation

For continuous (linear) scales on a color encoding, the gradientLength config can be used to control legend length.

Standard	With custom config

Unfortunately, this property has no effect when using discrete color scales, like quantile or quantize . As far as I could tell, the symbol config options don't control height either.

This can lead to legends that are much taller than their graph (see below: the gradientLength param is set, but it appears to have no effect.)

Quantize	Quantile

Proposed solution

• Add at least 1 configuration option for discrete color scales, perhaps setting the overall legend height (since the quantile mode won't have even tick sizes), in the direction of discreteColorLegendLength .
• If this property is added for Vega first, it will have to be propagated up to Vega-Lite separately.

Related PRs

• While searching for past legend issues, I found
  • Correctly Support Quantile, Quantize, Threshold Scales #1092 marked the introduction of quantile/quantize/threshold scales
  • vega/vega@ddd2bbf introduced discrete gradient legend