render-chart

render-chart

The user wants to see data as a chart. You have access to a renderer (lvc) that writes LiveCharts to a terminal. Pick the right mode for the situation, install the tool if it's missing, and either inline the result in your reply or hand the user a live window.

Decision: inline vs live window

Default to --no-color inline when you can read the chart — it keeps the conversation flowing and you can describe what's in it. Reserve --live for when there's genuinely no way to convey the information in monochrome glyphs.

Step 1 — make sure dotnet is installed

dotnet --version

If that errors, the user needs the .NET 8 SDK or runtime. Point them at https://dotnet.microsoft.com/download and stop — don't try to install it for them (admin install, varies per OS).

Step 2 — install lvc as a global tool (once)

dotnet tool install -g LiveChartsCore.Console.Cli

If they already have it, this errors with "already installed" — that's fine. Update with dotnet tool update -g LiveChartsCore.Console.Cli.

After install, lvc is on the user's PATH. Verify with:

lvc --json '{"kind":"line","series":[{"values":[1,2,3,2,1]}]}' --no-color

You should see a small Braille line chart in stdout.

Step 3 — write the JSON spec

Pass via --json '<spec>', --file path.json, or pipe stdin.

{
  "kind": "line",
  "title": "optional",
  "width": 70,
  "height": 20,
  "series": [
    {
      "name": "Signal",
      "values": [1, 2, 3, 4],
      "strokeThickness": 2
    }
  ],
  "xAxis": { "name": "X", "labels": ["a", "b", "c", "d"] },
  "yAxis": { "name": "Y" }
}

kind accepts: line, column, row, step, scatter, stackedcolumn, stackedrow, stackedarea, candlestick, box, pie, polar.

Series shape:

• values: number[] — line / column / row / step / stacked / pie / polar
• points: number[][] — scatter ([x, y]) / candlestick ([open, high, close, low]) / box ([max, q3, q1, median, min])
• strokeThickness: number — line / step (optional, default 1)

For pie: needs --width ≥ 80 --height ≥ 30 (outer labels collide otherwise). For stacked column / row with 2+ series: per-series textures auto-applied in plain mode; legend shows the texture next to each series name.

Step 4a — inline rendering (the common path)

lvc --json '<spec>' --no-color --width 70 --height 20

Capture the output and paste it back inside a fenced code block in your reply. CommonMark renders it monospace, the user sees the same glyphs you see.

Sizing: ~70×20 is a sweet spot. Smaller charts get cramped; larger ones might wrap weirdly in the user's terminal. Default to 70×20 unless the user asked otherwise.

Read what you rendered. Describe what's in it — "the blue series climbs from ~5 to ~12, the red oscillates around 8" — so the user can sanity-check it matches what they wanted. Don't claim "the chart looks correct" without naming the actual shapes you see.

Step 4b — live window (interactive / color path)

Spawn a new terminal so it doesn't block your conversation:

Windows (Windows Terminal):

Start-Process wt.exe -ArgumentList '-d', $pwd.Path, 'pwsh', '-NoExit', '-NoLogo', '-Command', 'lvc --live --file demo.json'

macOS (Terminal.app):

osascript -e "tell app \"Terminal\" to do script \"lvc --live --file $PWD/demo.json\""

Linux (GNOME Terminal):

gnome-terminal --working-directory="$PWD" -- lvc --live --file demo.json

For multi-line JSON, write a demo.json file first via the Write tool and pass --file — avoids cross-shell quoting hell.

Critical: you can't read the live window's contents. After launching, tell the user "I opened a chart in a new window — what do you see?" and iterate from their feedback. Don't fabricate a description of what's "probably there."

In the live window the user gets: mouse hover (tooltips), click-and-drag (pan), mouse wheel (zoom), q (quit), r (reset zoom), + / - (zoom at center).

Common pitfalls

• --live --no-color is an error: live mode redraws frames in place via ANSI escapes, which is exactly what --no-color strips. Pick one.
• --live with stdout redirected errors out — it needs a real TTY. Always spawn a new terminal window, never pipe --live output.
• --mode sixel --no-color errors out — Sixel is a binary escape sequence with no plain form. Drop --mode sixel or drop --no-color.
• Pie charts in plain mode at small canvases collapse the disc to a sliver because outer labels reserve margin space. Use --width 80 --height 30 minimum, or accept a smaller render in --live mode where the disc has full canvas.
• Stacked bar plain mode with 1 series keeps Braille ⣿ fills (no textures kick in until 2+ bar series exist). This is intentional.
• You cannot see colors in the user's terminal from your own output. Inline ANSI escapes you write get collapsed to one inline-code style by the CommonMark renderer — see [[reference_claude_code_cli_ansi_passthrough]]. This is why --no-color is the inline path: plain glyphs don't pretend to carry color information.

When NOT to use this skill

• The user asks to edit chart configuration in a LiveCharts app (XAML / source-code view) — that's a code-edit task, not a rendering task.
• The user wants to understand a chart they already have a screenshot of — use vision on the image, not lvc.
• The data is structural / hierarchical (trees, graphs, org charts) — lvc only handles statistical chart kinds.