svg

Overview ¶

Package svg is refract's built-in, zero-dependency SVG backend.

It emits SVG using nothing but the standard library. That is its whole reason to exist: the leanest use case — "give me a chart as SVG on a server" — should pull in no rendering engine, no font stack, and nothing young. Importing refract and this backend yields a stdlib-only dependency graph and a static binary.

Text ¶

Text is emitted as <text> elements, so the viewer or browser shapes it. For layout, this backend measures with internal/fontmetrics: exact advances when a font file is supplied via WithFont, and a built-in generic-sans table otherwise. Geometry is therefore identical to any other backend given identical metrics, but the metrics themselves differ slightly between backends, so the layout does too — the accepted imprecision in refract's "one model, identical output" promise. The bounds are measured in backend/gg/parity_test.go and explained in docs/adr/0003.

Determinism ¶

Attribute order and number formatting are fixed, and nothing here iterates a map or reads a clock, so the same chart produces byte-identical SVG on every run on a given machine.

Across architectures it does not, and no amount of care here would change that: Go may contract a*b+c into a fused multiply-add, arm64 does and amd64 does not, and a float32 coordinate can consequently differ in its last bit. Golden-file tests therefore compare with internal/svgdiff — everything but the numbers exactly, coordinates to within a hundredth of a pixel.