Style Defaults

Every chart takes one style object built with its *ChartDefaults factories. These rules keep the defaults the same across charts. Follow them when adding a chart, a style block, or a default.

Every default value lives in StyleDefaults in charts-core, including the chart-specific ones. Factories read their defaults from it and never repeat a literal, so the same element cannot differ between charts. The tables below list what it holds.

Factories

A chart's *ChartDefaults object has one factory per style block, plus style(). Users write every call against one object:

BarChartDefaults.style(
    axis = BarChartDefaults.axis(xLabels = BarChartDefaults.xLabels(maxCount = 4)),
)

Nesting stops at three levels: style, then a block, then axis labels. Axis labels are the only third level, and all Cartesian charts share them as AxisLabelStyle.
Every block gets a factory on the chart's own object, even when the block type is shared. HistogramChartDefaults forwards grid, axis, xLabels, yLabels and selection to BarChartDefaults, and its range keeps a zero minimum.
Forwarding factories repeat the default parameters, because Kotlin cannot forward them. Both read the same StyleDefaults value, and a test compares the two objects (BarStyleDefaultsTest).

Colors

Default colors come from MaterialTheme.colorScheme roles at full opacity, so they follow the app's theme in light and dark mode. Do not lower the alpha of a theme color, and do not check isSystemInDarkTheme(): the app's theme can differ from the system setting.

Element	Role	Charts
Series (bars, lines, fills, slices)	`primary`, or a palette from it	All
Points	`tertiary`	Line, radar (with `colorSameAsLine = false`)
Axis labels	`onSurfaceVariant`	Bar, histogram, line, stacked bar, stacked area, radar
Title	`onSurface`	All
Grid lines	`outlineVariant`	Bar, histogram, radar (rings and spokes)
Axis lines	`outline`	Bar, histogram, line
Selection line	`onSurface`	Bar, histogram, line, stacked bar, stacked area
Selection marker	`tertiary`	Line
Slice border	`surface`	Pie

Selection indicators draw on top of series marks. A selection default must never use the series role (primary or its palette), or it disappears over the selected mark.

Sizes

Sizes are Dp, so they scale with screen density. Point and marker sizes are radii.

Element	Default	Charts
Grid and axis lines	`1.dp`	Bar, histogram, line, radar
Selection line	`1.dp`	Bar, histogram, line, stacked bar, stacked area
Slice border	`1.dp`	Pie
Series line	`2.dp`	Line (`strokeWidth`), radar (`lineWidth`)
Points	`4.dp`	Line, radar (data points)
Selected point	`5.dp` (`selection.pointSize`)	Line, radar
Touch marker on the line	`3.dp` (`selection.markerSize`)	Line
Gap between an axis and its labels	`10.dp`	Bar, histogram, line, stacked bar, stacked area, radar
Radar label clamp margin	`6.dp`, only for a label that does not fit	Radar
Bar spacing	`10.dp`, `0.dp` on histogram	Bar, histogram, stacked bar
Minimum bar width	`10.dp`	Bar, histogram, stacked bar
Container padding	`15.dp`	All

Text

Element	Default	Charts
Title	`20.sp`, `ExtraBold`	All
Axis labels	`11.sp`	Bar, histogram, line, stacked bar, stacked area, radar

Alpha

Chart color alpha defaults to 1f, so the colors a user passes are drawn exactly as given. Users who want a softer look pass alpha themselves.

Setting	Default	Charts
Series `alpha`	`1f`	Bar, histogram, line, pie, stacked bar, stacked area
Polygon `fillAlpha`	`0.25f`	Radar
Selection `unselectedAlpha`	`0.7f`	Bar, histogram, stacked bar, stacked area, radar
Selection `unfocusedSeriesAlpha`	`0.35f`	Radar

Radar is the one exception to full-opacity fills. Radar polygons overlap each other and the grid, so a solid fill would hide the series behind it.

Selection dimming applies only while something is selected and multiplies the series alpha; it does not change the resting colors. unfocusedSeriesAlpha is lower than unselectedAlpha, because translucent radar fills barely change at 0.7f.

Do not add a default mark that draws in the series color on top of its own series, such as the removed stacked-area boundary line. At full opacity it cannot be seen.

Chart-specific defaults

Setting	Default	Charts
Grid steps	`4`	Bar, histogram, radar
Range	Fitted to the data, minimum `0.0` on histogram	Bar, histogram, line
Axis label `maxCount`	`null` (as many as fit)	Bar, histogram, line, stacked bar, stacked area
Curved lines (`bezier`)	`true` on line, `false` on stacked area	Line, stacked area
Points visible	`false`; the selected point is still drawn	Line, radar
Radar axis labels visible	`true`; the web shrinks to leave room for them	Radar
Radar points use line color	`true`	Radar
Donut hole	`0f` (full pie)	Pie
Zoom controls visible	`true`	Bar, histogram, line, stacked bar, stacked area
Legend visible	`true`	Line, pie; radar only with more than one series

Invalid values

Style values are never rejected; each chart draws a clamped copy of its style. Style Clamping describes the rules, and Validation Errors lists what is still an error.

Selection

A thin line cannot contrast with both the background and every bar color, so bar, histogram, and stacked bar charts let the selected bar mark the selection. The other bars dim to unselectedAlpha, and the selection line is drawn only over the background.

Stacked area follows the same rule. A column one data step wide around the selected point keeps full color, the rest of the stack dims, and the selection line stops at the top of the stack.

Radar has no selection line. Dragging selects an axis, and its per-axis marks are the points: the data points and labels of the other axes dim to unselectedAlpha. Polygons stay whole, because their shape is what a radar chart shows. Tapping a series outline focuses the series and fades the others to unfocusedSeriesAlpha.