Question: Add legend to columnchart clustered

[iilyak]

Currently the bars within the group do not have labels and legend is not provided. It is hard to tell that the bars are actually represent p99, p95, min, max

[iilyak]

I was able to add legend, but it would be really cool to have this functionality in CeTZ.

#let legend = (
  "p99": (stroke: black, fill: rgb("#3D5A80")),
  "p95": (stroke: black, fill: rgb("#98C1D9")),
  "min": (stroke: black, fill: rgb("#E0FBFC")),
  "max": (stroke: black, fill: rgb("#EE6C4D")),
)

#let legend-item(point, name, style) = {
  import cetz.draw: *
  content(
    (point.at(0)+2, point.at(1)+0), (point.at(0)+5, point.at(1)+0), 
    par(justify: false)[#name],
    frame: "rect",
    padding: .5em,
    fill: style.fill
  )
}

#let style(index) = legend.values().at(index)

#cetz.canvas({
  cetz.chart.columnchart(
    mode: "clustered",
    y-label: "ms",
    size: (auto, 5),
    label-key: 0,
    value-key: (..range(1, 5  )),
    bar-width: 0.9,
    bar-style: style,
    data3
  )

  let y = 4
  for (key, style) in legend {
    legend-item((4, y), key, style)
    y = y + 0.5
  }
})

Specifically what I don't like in the above solution is manual coordinates management.

[johannes-wolf]

I want to add a legend function for charts and plots, but I am not yet sure what a good API could look like.

[reitermarkus]

what a good API could look like.

Maybe a value-labels option, since this adds labels to each value, and a legend option to specify the position of those labels, e.g. legend: none | "left" | "right" | "bottom".

[johannes-wolf]

Implemented with #337.

Preview:

The chart API will use the plot API and therefore uses the same legend mechanism.
You can freely move the legend around or use some predefined anchors, see plot.plot for details.