Mark line and point

Target bands, threshold lines, and named points layered over cartesian data. Use it to explain thresholds, goals, anomalies, or operational bands directly on the chart. The screenshot is captured from the native Fission chart gallery.

What the chart is for

Mark line and point belongs to the Components and interaction family. Its job is to make this data shape readable: MarkArea, MarkLine, and MarkPoint records attached to a chart. In a production interface, choose this chart when the visual form makes the user's question faster to answer than a table or a simpler chart would.

Avoid it when the visual form makes the user estimate more than necessary; choose the simplest chart that answers the product question.

Data model

MarkArea, MarkLine, and MarkPoint records attached to a chart. Keep the data close to the type that describes it. Fission Charts is typed Rust, so a line uses LineSeries, a calendar heatmap uses CalendarHeatmapSeries, and chart components such as zoom, marks, and graphics are explicit fields on Chart rather than hidden string configuration.

Rust API

Field	Type	Notes
title	&str	Names the chart for the screen, accessibility tree, and test output.
mark_point	MarkPoint	Annotates a named data point.
mark_line	MarkLine	Draws a threshold or target line.
mark_area	MarkArea	Highlights a value band.
width / height	f32	Optional fixed size; omit them when the chart should flex inside Fission layout.

Example

use fission_charts::{Axis, Chart, LineSeries, MarkArea, MarkLine, MarkPoint};

let chart = Chart::new()
    .title("Markers and target band")
    .x_axis(Axis::category(vec!["Jan", "Feb", "Mar", "Apr", "May", "Jun"]))
    .y_axis(Axis::value())
    .mark_area(MarkArea::y_range("Target band", 120.0, 190.0))
    .mark_line(MarkLine::y("Target", 160.0))
    .mark_point(MarkPoint::xy("Peak", 4.0, 230.0))
    .series(vec![LineSeries::new("Revenue").data(vec![80.0, 132.0, 101.0, 184.0, 230.0, 210.0]).into()]);

Interaction and animation

Charts can emit typed ChartInteractionEvent values when interaction is enabled. Handle those events in a reducer when the app needs hover, press, release, scroll, selection, or brush behavior. ChartAnimation stores duration, delay, stagger, easing, and reduced-motion behavior as deterministic chart data, so animation timing can be tested instead of being hidden in ad-hoc timers.

Testing guidance

For this chart, test the data mapping first, then test lowering, then capture a live screenshot when visual output changes. The screenshot for this page is refreshed with npm run charts:generate from the website package.

Tags: markPoint, markLine, markArea.

Components and interaction family overview