Style
Every chart style default in one place, so the same element looks the same in every chart.
When adding a new default here, also update StyleDefaultsTest.defaults_matchCurrentValues with an assertion for the new property.
Properties
Axis label cap; null lets the chart choose how many labels fit.
Gap between an axis and its labels.
Axis labels: selectedValueFormatter without the .0 on whole values.
Gauges most often show a percentage, so the default range is 0..100.
Histogram bins touch, so there is no spacing between them.
A bin count of zero renders at the baseline.
The legend shows by default; it still hides itself without two items and a name.
Radius of the marker that follows the touch along the line.
Pie's selected slice share: selectedValueFormatter with a % suffix, e.g. 42.5%.
Points are hidden at rest; the selected point is drawn even when they are hidden.
Each category name sits at the end of its axis, so the web shrinks to leave room for them.
Radar polygons overlap each other and the grid, so a solid fill would hide the series behind it.
How far a radar label that does not fit stays from the canvas edge. It is not reserved from the web: such a label moves inside the canvas instead, so only a too small chart pays for it.
Lower than unselectedAlpha, because translucent radar fills barely change at that value.
Gap between neighbouring rings.
Widest a ring is drawn; rings get thinner when this many would not fit.
Radius of a point on the selected position, drawn larger than pointSize so it stands out.
Selected values in the title and legend: two decimals with trailing zeros trimmed, keeping .0 on whole values. For example: 3.0, 41.7, and 0.0.
Lines that draw a series, such as a line chart line or a radar polygon outline.
Maximum numeric Y-axis labels when the label count is unset; short plots show fewer.