The marks of a design drawn through the frame's scales (spec/14 §5, D-61).

generate/3 is one mark node as one Visualize.IR.Element group in the plot area's coordinates: its rows are the bound source through the mark's pipeline (rows/3, spec/14 §5.4), each channel is read from the rows and mapped through the scale it names in Visualize.Chart.Frame.scales/1 — the frame kind's table, renamed by the mark's scales node (spec/14 §5.1) — and every element is the generator's own — Visualize.Shape.Line, Visualize.Shape.Area, Visualize.Shape.Band, Visualize.Shape.Rule, Visualize.Shape.XBand, Visualize.Shape.PercentileBand, Visualize.Shape.Rose, Visualize.Shape.Symbol, Visualize.Shape.Pie over Visualize.Shape.Arc — fed the pixels the mark computed, so a mark is byte for byte the direct call with the same numbers. The four generic marks (path, rect, circle, arc) draw what a layout's rows carry. The mark's style resolves through Visualize.Chart.Style in the mode of the render target, and its paint, when the style gives none, is the theme's series colour for its position (spec/14 §5.6).

Examples

iex> chart =
...>   Visualize.Chart.from_map!(%{
...>     version: 2,
...>     sources: %{primary: %{fields: [:t, :v]}},
...>     frames: %{main: %{
...>       kind: :cartesian,
...>       margin: %{top: 0, right: 0, bottom: 0, left: 0},
...>       scales: %{x: %{kind: :linear}, y: %{kind: :linear}}
...>     }},
...>     marks: [%{type: :line, data: :primary, channels: %{x: :t, y: :v}}]
...>   })
iex> sources = %{primary: [%{t: 0, v: 0}, %{t: 1, v: 1}]}
iex> frame = Visualize.Chart.Frame.new(chart, sources: sources, size: {300, 200})
iex> group = Visualize.Chart.Mark.generate(frame, hd(chart.marks), sources: sources)
iex> group.style
%{class: "mark mark-line", fill: :none, stroke: "var(--vis-series-1, #3b6fa8)"}
iex> [path] = group.children
iex> Visualize.Backend.SVG.path_data(path.path)
"M0,200L300,0"