Module theme 

Chart theme — colors, typography, and shape defaults for chart chrome.

The Theme struct provides all chrome properties used by chart renderers: colors (axes, grid, text, background), typography (fonts and sizes for titles, labels, and numeric tick labels), and shape defaults (stroke weights, dot radii, corner radii, grid styling).

Plain values are written directly into SVG attributes, ensuring compatibility with every SVG renderer (browsers, resvg, Inkscape, etc.).

Browser theming

When charts are rendered in a browser, a <style> block inside the SVG maps element classes to CSS custom properties:

.axis-line { stroke: var(--chartml-axis-line) }
.grid-line { stroke: var(--chartml-grid) }

CSS specificity means these override the inline attribute defaults, so consuming apps can set --chartml-axis-line: #9ca3af on a parent element and charts respond instantly — no re-render needed.

Server-side rendering

For server-side rendering (e.g. render_to_png()), pass a Theme that matches your application’s current appearance. The same Theme used server-side should match the CSS custom properties set browser-side, ensuring visual parity between both rendering paths.

Example

use chartml_core::theme::Theme;

// Light mode (default)
let light = Theme::default();

// Dark mode
let dark = Theme::dark();

// Custom theme — `Theme` is `#[non_exhaustive]`, so consumers must
// start from `Theme::default()` or `Theme::dark()` and mutate fields.
// This makes adding new theme fields non-breaking forever.
let mut custom = Theme::dark();
custom.axis_line = "#9ca3af".into();
custom.grid = "#374151".into();

Structs

Theme

Chart theme — colors, typography, and shape defaults.

ZeroLineSpec

Specification for the zero-line (baseline) overlay on value axes.

Enums

BarCornerRadius

Which corners of a bar rect are rounded.

GridStyle

Grid line style — controls which gridlines are drawn.

TextTransform

Text transform applied to label text (tick labels, axis labels, legend).