Style Clamping

Charts never reject a style value. A value out of range is drawn as the closest value that makes sense, so a slider, an animation, or float math that lands on 1.0000001f never replaces a chart with an error.

Rules

A NaN size is usually Dp.Unspecified, which Compose uses to mean "use the default", so it falls back to the default of that size. No single size fits every element, and 0.dp would hide it. A NaN alpha has no such meaning, so 1f is enough. A text size is not a length, so clampTextSize also falls back for a non-sp unit and for zero, which would draw nothing.

The 16384 pixel cap keeps a size inside Compose layout limits. It depends on the screen density, which is why clampSize and clampTextSize take a Density.

Where it happens

• The helpers are clampAlpha(), clampSize(fallback, density), clampTextSize(fallback, density), and clampGridSteps() in StyleClamping.kt in charts-core.
• Each chart's style has a clamped(density) extension next to its style class, for example StackedAreaChartStyle.clamped in StackedAreaChartStyle.kt. It returns a copy with every number clamped.
• Each chart calls clamped() once, at its public entry point, as remember(style, density) { style.clamped(density) }, and passes the copy to its drawing code. Drawing code never clamps on its own.
• Factories and style constructors never clamp. A style keeps exactly what the user passed, so copy() and equality behave as users expect.

Adding a style value

• Give it a default in StyleDefaults.
• Clamp it in the chart's clamped(): alphas with clampAlpha(), sizes with clampSize() or clampTextSize(), and the same StyleDefaults value the factory uses as the fallback.
• Do not add a validation error for it.

Tests

• StyleClampingTest in charts-core covers each helper, including NaN, Dp.Unspecified, and an unspelled text unit.
• Line, radar, stacked bar, and stacked area each have a *_withInvalidNumericStyleValues_drawsClampedChart test that draws the chart with out-of-range values and checks that no error appears.
• BarStyleDefaultsTest checks the clamped bar values, which histogram shares. Pie has no clamping test.