Documentation
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Overview ¶
Package render carries the cross-renderer surface: the Renderer interface every output backend satisfies, the RenderOpts shape, and the RenderPrecision constant that pins float formatting across the SVG (P05), PNG (P12), PDF (P15), and canvas-JSON (P12) backends.
Concrete renderers live in subpackages (render/svg/, render/pdf/, render/canvas/). All three consume the same scene.SceneDoc shape.
Index ¶
Constants ¶
const RenderPrecision = 3
RenderPrecision pins float-to-string precision across every renderer for cross-impl + cross-Go-version stability. SVG goldens and the JS port's Canvas output both anchor on this constant. 3 decimals = sub-millimetre at typical chart sizes; no perceivable visual difference vs higher precision. JS port matches via the scene-JSON having pre-rounded floats (the encoder snaps before emitting).
Variables ¶
This section is empty.
Functions ¶
func FormatFloat ¶
FormatFloat renders v with RenderPrecision decimal places, trimming trailing zeros after the decimal point and dropping the decimal point itself when no fractional part remains (so "1.000" → "1", "1.230" → "1.23"). Matches D3's default formatting and keeps goldens diff-friendly.
NaN and +/-Inf coordinates are rendered as "0" defensively — the encoder is responsible for catching non-finite values upstream and raising PRISM_RENDER_001; the renderer's job is to never emit broken SVG even when handed garbage.
Types ¶
type RenderOpts ¶
type RenderOpts struct {
// Format is the requested output format ("svg" | "png" | "pdf" |
// "canvas-json"). The CLI rejects formats the runtime cannot
// produce with PRISM_RENDER_FORMAT_UNAVAILABLE.
Format string
// Width overrides the scene's natural width. 0 = use the scene's.
Width float64
// Height overrides the scene's natural height. 0 = use the scene's.
Height float64
// Theme overrides SceneDoc.Theme. nil = use the doc's.
Theme *scene.Theme
// Background overrides the theme's background ("transparent",
// "#fff", "rgba(0,0,0,0.5)", etc.). "" = use the theme's.
Background string
// Paginate is PDF-only (P15). One chart per page.
Paginate bool
// DPI is PNG-only (P12).
DPI float64
}
RenderOpts carries the runtime knobs every renderer accepts. Zero values are sensible: 0 dimensions = use the scene's natural width/height; nil Theme = use the scene's Theme.
type Renderer ¶
type Renderer interface {
// Render produces output bytes for the SceneDoc + opts. The
// returned bytes are renderer-format-specific; callers route them
// through MimeType() for HTTP / display contexts.
Render(doc *scene.SceneDoc, opts RenderOpts) ([]byte, error)
// MimeType returns the canonical MIME type for the renderer's
// output (image/svg+xml, image/png, application/pdf, etc.).
MimeType() string
}
Renderer is the contract every output-format backend satisfies. The SVG impl ships in P05; PNG (via resvg-go) lands in P12, PDF in P15, canvas-json in P12.
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