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* An SVG picture, replayed as canvas drawing calls.
*
* This exists for one reason: the PDF export must stay a real vector export.
*
* Every figure in this app is a {@link PlotFigure} — an object with a `draw(ctx,
* box)` that is handed *some* context and draws into it. On screen that context
* belongs to a canvas; in an export it is a {@link VectorPage}, which turns the
* same calls into PDF operators. That indirection is the whole reason a plot
* leaves this application as paths and text rather than as a photograph of
* pixels, and it is not something a charting library gives away: a library
* paints into a canvas of its own, and what comes back is an image.
*
* So the library is asked for SVG instead — `zrender`'s SVG renderer, which is
* what ECharts draws with here — and this module reads that SVG back out and
* issues the equivalent canvas calls. One implementation then serves both
* paths: the screen gets the calls on a real context, the PDF gets the same
* calls on a page, and the two cannot drift, because they are the same drawing
* twice rather than two drawings of the same data.
*
* The vocabulary handled is the one `zrender` emits, which is small and worth
* naming: `<g transform>`, `<path d>` (`M L H V C S Q T A Z`, absolute and
* relative), `<rect>`, `<circle>`, `<ellipse>`, `<line>`, `<polyline>`,
* `<polygon>`, `<text>`/`<tspan>`, `<defs>` holding `<clipPath>` and gradients,
* and `<style>`, which carries only `:hover` rules and is therefore ignored.
*
* Three limits, stated rather than hidden:
*
* - **A linear gradient is bands.** A canvas context can hold a
* `CanvasGradient`, but a {@link VectorPage} holds only the radial one its
* structure painter asks for — so a shape filled with a linear one is clipped to and filled with a
* hundred bands across the gradient's line, each the colour the gradient has
* at its middle. That is what a chart's continuous colour bar is: it used to
* be flattened to its middle stop, and every exported pileup's key was one
* orange rectangle beside a picture in a hundred colours. A radial gradient,
* which nothing here draws, is still its middle stop; a gradient stroke is
* too.
* - **`<image>` is skipped.** Nothing `zrender` draws for these charts is a
* raster; a contact map, which genuinely is one, is not drawn through here at
* all (`ui/analysisPlots.ts` keeps its own painter).
* - **Arc flags must be separated.** SVG allows `a1 1 0 11 5 5`, gluing the two
* one-character flags to their neighbours. The scanner below reads them as
* single characters, so that form works too — but a flag written as anything
* other than `0` or `1` is refused rather than guessed at.
*/
import { pdfColour, type VectorTarget } from '../ui/vector'
/** The slice of a canvas context a replay needs. A real one satisfies it. */
export type PaintTarget = VectorTarget
/** The size to paint at, when it differs from the picture's own. */
export interface PaintBox {
width: number
height: number
}
// ---------------------------------------------------------------------------
// Inherited paint state
// ---------------------------------------------------------------------------
interface PaintState {
/** `null` is SVG's `none`: the shape is not filled at all. */
fill: string | null
/**
* The linear gradient a shape is filled with, where it is one; {@link fill}
* is then its middle stop, for the text and the strokes that cannot be
* banded.
*/
fillGradient: LinearPaint | null
stroke: string | null
strokeWidth: number
opacity: number
fillOpacity: number
strokeOpacity: number
lineCap: CanvasLineCap
lineJoin: CanvasLineJoin
dash: number[]
fontSize: number
fontFamily: string
fontWeight: string
fontStyle: string
anchor: CanvasTextAlign
baseline: CanvasTextBaseline
/** Which of fill and stroke is laid down first, from `paint-order`. */
strokeFirst: boolean
}
const INITIAL: PaintState = {
fill: '#000000',
fillGradient: null,
stroke: null,
strokeWidth: 1,
opacity: 1,
fillOpacity: 1,
strokeOpacity: 1,
lineCap: 'butt',
lineJoin: 'miter',
dash: [],
fontSize: 12,
fontFamily: 'sans-serif',
fontWeight: 'normal',
fontStyle: 'normal',
anchor: 'left',
baseline: 'alphabetic',
strokeFirst: false,
}
/**
* A presentation property, from the `style` attribute or the attribute itself.
*
* CSS wins, which is what a browser does and what `zrender` relies on: it puts
* the font in `style` and the colours in attributes, on the same element.
*/
function prop(el: Element, inline: Map<string, string>, name: string): string | null {
const styled = inline.get(name)
if (styled !== undefined && styled !== '') return styled
const attr = el.getAttribute(name)
return attr === null || attr === '' ? null : attr
}
function inlineStyle(el: Element): Map<string, string> {
const map = new Map<string, string>()
const text = el.getAttribute('style')
if (text === null) return map
for (const rule of text.split(';')) {
const colon = rule.indexOf(':')
if (colon < 0) continue
map.set(rule.slice(0, colon).trim().toLowerCase(), rule.slice(colon + 1).trim())
}
return map
}
function num(text: string | null, fallback: number): number {
if (text === null) return fallback
const value = Number.parseFloat(text)
return Number.isFinite(value) ? value : fallback
}
function alignOf(text: string | null, fallback: CanvasTextAlign): CanvasTextAlign {
if (text === 'middle') return 'center'
if (text === 'end') return 'right'
if (text === 'start') return 'left'
return fallback
}
function baselineOf(text: string | null, fallback: CanvasTextBaseline): CanvasTextBaseline {
switch (text) {
case 'central':
case 'middle':
return 'middle'
case 'hanging':
case 'text-before-edge':
return 'top'
case 'text-after-edge':
case 'ideographic':
return 'bottom'
case 'alphabetic':
case 'auto':
return 'alphabetic'
default:
return fallback
}
}
function dashOf(text: string | null): number[] | null {
if (text === null || text === 'none') return null
const parts = text
.split(/[\s,]+/)
.filter((piece) => piece !== '')
.map((piece) => Number.parseFloat(piece))
if (parts.length === 0 || parts.some((on) => !Number.isFinite(on) || on < 0)) return []
return parts
}
/** The state an element's own attributes make out of the one it inherited. */
function descend(el: Element, parent: PaintState, paints: Paints): PaintState {
const inline = inlineStyle(el)
const next: PaintState = { ...parent }
const fill = prop(el, inline, 'fill')
if (fill !== null) {
next.fill = colourOf(fill, parent.fill, paints)
next.fillGradient = gradientOf(fill, parent.fillGradient, paints)
}
const stroke = prop(el, inline, 'stroke')
if (stroke !== null) next.stroke = colourOf(stroke, parent.stroke, paints)
const width = prop(el, inline, 'stroke-width')
if (width !== null) next.strokeWidth = num(width, parent.strokeWidth)
const opacity = prop(el, inline, 'opacity')
if (opacity !== null) next.opacity = parent.opacity * clamp01(num(opacity, 1))
const fillOpacity = prop(el, inline, 'fill-opacity')
if (fillOpacity !== null) next.fillOpacity = clamp01(num(fillOpacity, 1))
const strokeOpacity = prop(el, inline, 'stroke-opacity')
if (strokeOpacity !== null) next.strokeOpacity = clamp01(num(strokeOpacity, 1))
const cap = prop(el, inline, 'stroke-linecap')
if (cap === 'round' || cap === 'square' || cap === 'butt') next.lineCap = cap
const join = prop(el, inline, 'stroke-linejoin')
if (join === 'round' || join === 'bevel' || join === 'miter') next.lineJoin = join
const dash = dashOf(prop(el, inline, 'stroke-dasharray'))
if (dash !== null) next.dash = dash
const size = prop(el, inline, 'font-size')
if (size !== null) next.fontSize = num(size, parent.fontSize)
const family = prop(el, inline, 'font-family')
if (family !== null) next.fontFamily = family
const weight = prop(el, inline, 'font-weight')
if (weight !== null) next.fontWeight = weight
const style = prop(el, inline, 'font-style')
if (style !== null) next.fontStyle = style
next.anchor = alignOf(prop(el, inline, 'text-anchor'), parent.anchor)
next.baseline = baselineOf(
prop(el, inline, 'dominant-baseline') ?? prop(el, inline, 'alignment-baseline'),
parent.baseline,
)
const order = prop(el, inline, 'paint-order')
if (order !== null) next.strokeFirst = order.trim().split(/\s+/)[0] === 'stroke'
return next
}
function clamp01(value: number): number {
return value < 0 ? 0 : value > 1 ? 1 : value
}
/**
* A linear gradient as SVG states it: the line it runs along, in the shape's
* own box (`objectBoundingBox`, the default) or in the user space the shape is
* drawn in, and its stops in order.
*/
interface LinearPaint {
units: 'objectBoundingBox' | 'userSpaceOnUse'
x1: number
y1: number
x2: number
y2: number
stops: Array<{ offset: number; rgb: [number, number, number]; opacity: number }>
}
/**
* Every gradient in the document, by id: the colour it stands for where only
* one colour can be drawn — a stroke, a run of text, a radial gradient — and,
* for a linear one, the gradient itself, for a fill to be banded with.
*/
type Paints = Map<string, { flat: string; linear: LinearPaint | null }>
/** The `#id` a `url(#id)` paint names, or `null` for any other paint. */
function urlOf(text: string): string | null {
return /^url\(\s*['"]?#([^)'"]+)['"]?\s*\)$/.exec(text.trim())?.[1] ?? null
}
/**
* A paint value as a colour, or `null` for `none`.
*
* `url(#id)` is a gradient, which a colour string cannot be; the table built
* by {@link collectPaints} holds the one stop that stands for each.
*/
function colourOf(value: string, inherited: string | null, paints: Paints): string | null {
const text = value.trim()
if (text === 'none' || text === 'transparent') return null
if (text === 'currentColor' || text === 'inherit') return inherited
const url = urlOf(text)
if (url !== null) return paints.get(url)?.flat ?? null
return text
}
/** The linear gradient a fill names, or `null` where it names anything else. */
function gradientOf(value: string, inherited: LinearPaint | null, paints: Paints): LinearPaint | null {
const text = value.trim()
if (text === 'inherit') return inherited
const url = urlOf(text)
return url === null ? null : (paints.get(url)?.linear ?? null)
}
/**
* Every gradient in the document.
*
* Its single colour is the middle stop rather than the first, because a
* gradient is chosen for the colour it reads as overall and its ends are the
* extremes of that, not the average of it.
*/
function collectPaints(root: Element): Paints {
const paints: Paints = new Map()
const gradients = root.querySelectorAll('linearGradient, radialGradient')
for (const gradient of Array.from(gradients)) {
const id = gradient.getAttribute('id')
if (id === null) continue
const stops = Array.from(gradient.querySelectorAll('stop'))
if (stops.length === 0) continue
const middle = stops[Math.floor((stops.length - 1) / 2)]
const flat = prop(middle, inlineStyle(middle), 'stop-color') ?? '#000000'
paints.set(id, {
flat,
linear: gradient.tagName.toLowerCase() === 'lineargradient' ? linearOf(gradient, stops) : null,
})
}
return paints
}
/**
* A `<linearGradient>` read whole. Offsets are fractions or percentages and
* never run backwards, as SVG has them; the line defaults to left to right
* across the shape's box.
*/
function linearOf(gradient: Element, stops: Element[]): LinearPaint {
const fraction = (text: string | null, fallback: number): number => {
if (text === null || text.trim() === '') return fallback
const value = Number.parseFloat(text)
if (!Number.isFinite(value)) return fallback
return text.trim().endsWith('%') ? value / 100 : value
}
let last = 0
return {
units: gradient.getAttribute('gradientUnits') === 'userSpaceOnUse' ? 'userSpaceOnUse' : 'objectBoundingBox',
x1: fraction(gradient.getAttribute('x1'), 0),
y1: fraction(gradient.getAttribute('y1'), 0),
x2: fraction(gradient.getAttribute('x2'), 1),
y2: fraction(gradient.getAttribute('y2'), 0),
stops: stops.map((stop) => {
const inline = inlineStyle(stop)
last = Math.max(last, clamp01(fraction(stop.getAttribute('offset'), 0)))
return {
offset: last,
rgb: pdfColour(prop(stop, inline, 'stop-color') ?? '#000000'),
opacity: clamp01(num(prop(stop, inline, 'stop-opacity'), 1)),
}
}),
}
}
// ---------------------------------------------------------------------------
// Transforms
// ---------------------------------------------------------------------------
type Matrix = [number, number, number, number, number, number]
/**
* An SVG `transform` attribute as one matrix.
*
* Applied to the context with `transform` rather than `setTransform`, so it
* composes with wherever the caller already placed the figure.
*/
export function parseTransform(text: string): Matrix {
let out: Matrix = [1, 0, 0, 1, 0, 0]
const each = /(matrix|translate|scale|rotate|skewX|skewY)\s*\(([^)]*)\)/g
let found: RegExpExecArray | null
while ((found = each.exec(text)) !== null) {
const args = found[2]
.split(/[\s,]+/)
.filter((piece) => piece !== '')
.map((piece) => Number.parseFloat(piece))
.map((value) => (Number.isFinite(value) ? value : 0))
out = compose(out, single(found[1], args))
}
return out
}
function single(kind: string, a: number[]): Matrix {
switch (kind) {
case 'matrix':
return [a[0] ?? 1, a[1] ?? 0, a[2] ?? 0, a[3] ?? 1, a[4] ?? 0, a[5] ?? 0]
case 'translate':
return [1, 0, 0, 1, a[0] ?? 0, a[1] ?? 0]
case 'scale': {
const sx = a[0] ?? 1
return [sx, 0, 0, a[1] ?? sx, 0, 0]
}
case 'rotate': {
const angle = ((a[0] ?? 0) * Math.PI) / 180
const cos = Math.cos(angle)
const sin = Math.sin(angle)
const turn: Matrix = [cos, sin, -sin, cos, 0, 0]
if (a.length < 3) return turn
const cx = a[1]
const cy = a[2]
return compose(compose([1, 0, 0, 1, cx, cy], turn), [1, 0, 0, 1, -cx, -cy])
}
case 'skewX':
return [1, 0, Math.tan(((a[0] ?? 0) * Math.PI) / 180), 1, 0, 0]
case 'skewY':
return [1, Math.tan(((a[0] ?? 0) * Math.PI) / 180), 0, 1, 0, 0]
default:
return [1, 0, 0, 1, 0, 0]
}
}
function compose(m: Matrix, n: Matrix): Matrix {
return [
m[0] * n[0] + m[2] * n[1],
m[1] * n[0] + m[3] * n[1],
m[0] * n[2] + m[2] * n[3],
m[1] * n[2] + m[3] * n[3],
m[0] * n[4] + m[2] * n[5] + m[4],
m[1] * n[4] + m[3] * n[5] + m[5],
]
}
const IDENTITY: Matrix = [1, 0, 0, 1, 0, 0]
function isIdentity(m: Matrix): boolean {
return m[0] === 1 && m[1] === 0 && m[2] === 0 && m[3] === 1 && m[4] === 0 && m[5] === 0
}
// ---------------------------------------------------------------------------
// Path data
// ---------------------------------------------------------------------------
/**
* A `d` attribute, issued as path calls on the context.
*
* The scanner is positional rather than a token list, for one reason: an arc's
* two flags are single characters that may be glued to the numbers around them
* (`a1 1 0 11 5 5` is legal and means flags `1` and `1`), and a tokeniser that
* read numbers greedily would see `11` and mis-shape the curve.
*
* Arcs are converted to cubics here rather than passed on, because a canvas has
* no elliptical-arc-to and the conversion is exact for the segments the
* standard decomposition produces.
*/
export function paintPath(ctx: PaintTarget, d: string): void {
let at = 0
const skip = (): void => {
while (at < d.length && (d[at] === ' ' || d[at] === ',' || d[at] === '\n' || d[at] === '\t' || d[at] === '\r')) {
at += 1
}
}
const number = (): number => {
skip()
const start = at
if (d[at] === '+' || d[at] === '-') at += 1
while (at < d.length && d[at] >= '0' && d[at] <= '9') at += 1
if (d[at] === '.') {
at += 1
while (at < d.length && d[at] >= '0' && d[at] <= '9') at += 1
}
if (d[at] === 'e' || d[at] === 'E') {
at += 1
if (d[at] === '+' || d[at] === '-') at += 1
while (at < d.length && d[at] >= '0' && d[at] <= '9') at += 1
}
const value = Number.parseFloat(d.slice(start, at))
return Number.isFinite(value) ? value : Number.NaN
}
const flag = (): number => {
skip()
const ch = d[at]
if (ch === '0' || ch === '1') {
at += 1
return ch === '1' ? 1 : 0
}
return Number.NaN
}
const more = (): boolean => {
skip()
const ch = d[at]
return ch !== undefined && (ch === '+' || ch === '-' || ch === '.' || (ch >= '0' && ch <= '9'))
}
let x = 0
let y = 0
let startX = 0
let startY = 0
/** The reflection point `S` and `T` need, or `null` after any other command. */
let lastCubic: { x: number; y: number } | null = null
let lastQuad: { x: number; y: number } | null = null
let open = false
const move = (nx: number, ny: number): void => {
ctx.moveTo(nx, ny)
x = nx
y = ny
startX = nx
startY = ny
open = true
}
const line = (nx: number, ny: number): void => {
if (!open) move(nx, ny)
else {
ctx.lineTo(nx, ny)
x = nx
y = ny
}
}
const cubic = (
c1x: number, c1y: number, c2x: number, c2y: number, nx: number, ny: number,
): void => {
if (!open) move(x, y)
ctx.bezierCurveTo(c1x, c1y, c2x, c2y, nx, ny)
x = nx
y = ny
}
let code = ''
skip()
while (at < d.length) {
const ch = d[at]
if (/[MmLlHhVvCcSsQqTtAaZz]/.test(ch)) {
code = ch
at += 1
} else if (code === '') {
// Junk before any command: nothing can be drawn from it.
return
} else if (code === 'M') {
code = 'L'
} else if (code === 'm') {
code = 'l'
}
const rel = code === code.toLowerCase()
const ox = rel ? x : 0
const oy = rel ? y : 0
switch (code.toUpperCase()) {
case 'Z': {
ctx.closePath()
x = startX
y = startY
lastCubic = null
lastQuad = null
// `Z` has no implicit repeat, so the next thing must be a command
// letter; forgetting the code is what makes a stray number end the
// walk instead of closing the same subpath for ever.
code = ''
skip()
continue
}
case 'M': {
move(ox + number(), oy + number())
lastCubic = null
lastQuad = null
break
}
case 'L': {
line(ox + number(), oy + number())
lastCubic = null
lastQuad = null
break
}
case 'H': {
line(ox + number(), y)
lastCubic = null
lastQuad = null
break
}
case 'V': {
line(x, oy + number())
lastCubic = null
lastQuad = null
break
}
case 'C': {
const c1x = ox + number()
const c1y = oy + number()
const c2x = ox + number()
const c2y = oy + number()
const nx = ox + number()
const ny = oy + number()
cubic(c1x, c1y, c2x, c2y, nx, ny)
lastCubic = { x: c2x, y: c2y }
lastQuad = null
break
}
case 'S': {
const c1x: number = lastCubic === null ? x : 2 * x - lastCubic.x
const c1y: number = lastCubic === null ? y : 2 * y - lastCubic.y
const c2x = ox + number()
const c2y = oy + number()
const nx = ox + number()
const ny = oy + number()
cubic(c1x, c1y, c2x, c2y, nx, ny)
lastCubic = { x: c2x, y: c2y }
lastQuad = null
break
}
case 'Q': {
const cx = ox + number()
const cy = oy + number()
const nx = ox + number()
const ny = oy + number()
if (!open) move(x, y)
ctx.quadraticCurveTo(cx, cy, nx, ny)
x = nx
y = ny
lastQuad = { x: cx, y: cy }
lastCubic = null
break
}
case 'T': {
const cx: number = lastQuad === null ? x : 2 * x - lastQuad.x
const cy: number = lastQuad === null ? y : 2 * y - lastQuad.y
const nx = ox + number()
const ny = oy + number()
if (!open) move(x, y)
ctx.quadraticCurveTo(cx, cy, nx, ny)
x = nx
y = ny
lastQuad = { x: cx, y: cy }
lastCubic = null
break
}
case 'A': {
const rx = number()
const ry = number()
const angle = number()
const large = flag()
const sweep = flag()
const nx = ox + number()
const ny = oy + number()
if (Number.isNaN(large) || Number.isNaN(sweep) || Number.isNaN(nx) || Number.isNaN(ny)) {
return
}
if (!open) move(x, y)
for (const seg of arcToCubics(x, y, rx, ry, angle, large === 1, sweep === 1, nx, ny)) {
ctx.bezierCurveTo(seg[0], seg[1], seg[2], seg[3], seg[4], seg[5])
}
x = nx
y = ny
lastCubic = null
lastQuad = null
break
}
default:
return
}
if (Number.isNaN(x) || Number.isNaN(y)) return
skip()
if (!more() && at < d.length && !/[MmLlHhVvCcSsQqTtAaZz]/.test(d[at])) return
}
}
/**
* An elliptical arc as a run of cubics.
*
* The endpoint parameterisation SVG uses turned into the centre one, then split
* into segments of at most a quarter turn — the span over which the standard
* `4/3·tan(θ/4)` handle is accurate to well under a printed pixel.
*/
export function arcToCubics(
x1: number, y1: number,
rxIn: number, ryIn: number,
degrees: number,
large: boolean,
sweep: boolean,
x2: number, y2: number,
): Array<[number, number, number, number, number, number]> {
let rx = Math.abs(rxIn)
let ry = Math.abs(ryIn)
// A zero radius is a straight line, per the specification.
if (rx === 0 || ry === 0) return [[x1, y1, x2, y2, x2, y2]]
const phi = (degrees * Math.PI) / 180
const cos = Math.cos(phi)
const sin = Math.sin(phi)
const dx = (x1 - x2) / 2
const dy = (y1 - y2) / 2
const x1p = cos * dx + sin * dy
const y1p = -sin * dx + cos * dy
// Radii too small to reach the endpoint are scaled up until they just do.
const lambda = (x1p * x1p) / (rx * rx) + (y1p * y1p) / (ry * ry)
if (lambda > 1) {
const grow = Math.sqrt(lambda)
rx *= grow
ry *= grow
}
const sign = large === sweep ? -1 : 1
const top = rx * rx * ry * ry - rx * rx * y1p * y1p - ry * ry * x1p * x1p
const bottom = rx * rx * y1p * y1p + ry * ry * x1p * x1p
const factor = bottom === 0 ? 0 : sign * Math.sqrt(Math.max(0, top / bottom))
const cxp = (factor * rx * y1p) / ry
const cyp = (-factor * ry * x1p) / rx
const cx = cos * cxp - sin * cyp + (x1 + x2) / 2
const cy = sin * cxp + cos * cyp + (y1 + y2) / 2
const angleOf = (ux: number, uy: number): number => Math.atan2(uy, ux)
const start = angleOf((x1p - cxp) / rx, (y1p - cyp) / ry)
const end = angleOf((-x1p - cxp) / rx, (-y1p - cyp) / ry)
let span = end - start
if (!sweep && span > 0) span -= 2 * Math.PI
if (sweep && span < 0) span += 2 * Math.PI
const steps = Math.max(1, Math.ceil(Math.abs(span) / (Math.PI / 2)))
const step = span / steps
const handle = (4 / 3) * Math.tan(step / 4)
const out: Array<[number, number, number, number, number, number]> = []
const at = (angle: number): [number, number] => [
cx + rx * Math.cos(angle) * cos - ry * Math.sin(angle) * sin,
cy + rx * Math.cos(angle) * sin + ry * Math.sin(angle) * cos,
]
const slope = (angle: number): [number, number] => [
-rx * Math.sin(angle) * cos - ry * Math.cos(angle) * sin,
-rx * Math.sin(angle) * sin + ry * Math.cos(angle) * cos,
]
for (let i = 0; i < steps; i++) {
const a0 = start + i * step
const a1 = a0 + step
const [px, py] = at(a0)
const [qx, qy] = at(a1)
const [dpx, dpy] = slope(a0)
const [dqx, dqy] = slope(a1)
out.push([
px + handle * dpx, py + handle * dpy,
qx - handle * dqx, qy - handle * dqy,
qx, qy,
])
}
return out
}
// ---------------------------------------------------------------------------
// The walk
// ---------------------------------------------------------------------------
/** Parse an SVG document and paint it. See {@link paintSvgElement}. */
export function paintSvgString(svg: string, ctx: PaintTarget, box?: PaintBox): void {
const parsed = new DOMParser().parseFromString(svg, 'image/svg+xml')
const root = parsed.documentElement
if (root === null || root.nodeName === 'parsererror') return
paintSvgElement(root, ctx, box)
}
/**
* Paint an `<svg>` element's contents onto a context.
*
* `box` scales the picture to a size other than its own — a PNG exported at
* twice the screen size, say — by the one transform that keeps it a drawing
* rather than an enlargement of pixels.
*/
export function paintSvgElement(root: Element, ctx: PaintTarget, box?: PaintBox): void {
const size = sizeOf(root)
const paints = collectPaints(root)
const clips = collectClips(root)
ctx.save()
if (box !== undefined && size !== null && size.width > 0 && size.height > 0) {
const sx = box.width / size.width
const sy = box.height / size.height
if (sx !== 1 || sy !== 1) ctx.transform(sx, 0, 0, sy, 0, 0)
}
// The viewBox's own origin, so a picture that does not start at (0, 0) lands
// where it says it does.
if (size !== null && (size.x !== 0 || size.y !== 0)) ctx.transform(1, 0, 0, 1, -size.x, -size.y)
walk(root, ctx, INITIAL, paints, clips)
ctx.restore()
}
/** The picture's own coordinate box, from `viewBox` or `width`/`height`. */
function sizeOf(root: Element): { x: number; y: number; width: number; height: number } | null {
const view = root.getAttribute('viewBox')
if (view !== null) {
const parts = view
.split(/[\s,]+/)
.filter((piece) => piece !== '')
.map((piece) => Number.parseFloat(piece))
if (parts.length === 4 && parts.every((value) => Number.isFinite(value))) {
return { x: parts[0], y: parts[1], width: parts[2], height: parts[3] }
}
}
const width = num(root.getAttribute('width'), Number.NaN)
const height = num(root.getAttribute('height'), Number.NaN)
if (!Number.isFinite(width) || !Number.isFinite(height)) return null
return { x: 0, y: 0, width, height }
}
/** Every `<clipPath>` in the document, by id. */
function collectClips(root: Element): Map<string, Element> {
const clips = new Map<string, Element>()
for (const clip of Array.from(root.querySelectorAll('clipPath'))) {
const id = clip.getAttribute('id')
if (id !== null) clips.set(id, clip)
}
return clips
}
const SKIP = new Set(['defs', 'style', 'clippath', 'lineargradient', 'radialgradient', 'title', 'desc', 'metadata', 'filter', 'mask', 'pattern', 'marker', 'symbol'])
function walk(
el: Element,
ctx: PaintTarget,
inherited: PaintState,
paints: Paints,
clips: Map<string, Element>,
): void {
for (const child of Array.from(el.children)) {
const tag = child.tagName.toLowerCase()
if (SKIP.has(tag)) continue
const state = descend(child, inherited, paints)
const matrix = transformOf(child)
const clip = clipOf(child, clips)
const framed = !isIdentity(matrix) || clip !== null
if (framed) ctx.save()
if (!isIdentity(matrix)) ctx.transform(...matrix)
if (clip !== null) applyClip(ctx, clip, clips)
if (tag === 'g' || tag === 'a' || tag === 'svg') {
walk(child, ctx, state, paints, clips)
} else {
shape(child, tag, ctx, state)
}
if (framed) ctx.restore()
}
}
function transformOf(el: Element): Matrix {
const text = el.getAttribute('transform')
return text === null || text === '' ? IDENTITY : parseTransform(text)
}
function clipOf(el: Element, clips: Map<string, Element>): Element | null {
const text = el.getAttribute('clip-path') ?? inlineStyle(el).get('clip-path') ?? null
if (text === null) return null
const url = /^url\(\s*['"]?#([^)'"]+)['"]?\s*\)$/.exec(text.trim())
if (url === null) return null
return clips.get(url[1]) ?? null
}
/**
* A `<clipPath>`, as a clip on the context.
*
* Every child contributes to one path, which is what SVG says a clip path is:
* the union of its shapes. Nothing inside it is filled or stroked.
*/
function applyClip(ctx: PaintTarget, clip: Element, clips: Map<string, Element>): void {
ctx.beginPath()
let any = false
for (const child of Array.from(clip.children)) {
const matrix = transformOf(child)
// A transform on a clip child would have to move the path's own points,
// since the clip is built as one path; identity is what `zrender` emits and
// anything else is skipped rather than silently mis-clipped.
if (!isIdentity(matrix)) continue
if (outline(child, child.tagName.toLowerCase(), ctx)) any = true
}
const nested = clipOf(clip, clips)
if (nested !== null) applyClip(ctx, nested, clips)
if (any) ctx.clip()
}
/**
* The geometry of one shape, added to the current path.
*
* Split out from {@link shape} because a clip path needs exactly this and none
* of the painting.
*/
function outline(el: Element, tag: string, ctx: PaintTarget): boolean {
switch (tag) {
case 'path': {
const d = el.getAttribute('d')
if (d === null || d === '') return false
paintPath(ctx, d)
return true
}
case 'rect': {
const x = num(el.getAttribute('x'), 0)
const y = num(el.getAttribute('y'), 0)
const width = num(el.getAttribute('width'), 0)
const height = num(el.getAttribute('height'), 0)
if (!(width > 0) || !(height > 0)) return false
const rx = Math.min(num(el.getAttribute('rx'), 0), width / 2)
const ry = Math.min(num(el.getAttribute('ry'), rx), height / 2)
if (rx > 0 && ry > 0) roundedRect(ctx, x, y, width, height, rx, ry)
else ctx.rect(x, y, width, height)
return true
}
case 'circle': {
const r = num(el.getAttribute('r'), 0)
if (!(r > 0)) return false
ctx.moveTo(num(el.getAttribute('cx'), 0) + r, num(el.getAttribute('cy'), 0))
ctx.arc(num(el.getAttribute('cx'), 0), num(el.getAttribute('cy'), 0), r, 0, Math.PI * 2)
return true
}
case 'ellipse': {
const rx = num(el.getAttribute('rx'), 0)
const ry = num(el.getAttribute('ry'), 0)
if (!(rx > 0) || !(ry > 0)) return false
// As an arc, since `ellipse` is not in the slice of the context this can
// count on; the four-cubic decomposition is the same one an arc gets.
const cx = num(el.getAttribute('cx'), 0)
const cy = num(el.getAttribute('cy'), 0)
ctx.moveTo(cx + rx, cy)
for (const seg of arcToCubics(cx + rx, cy, rx, ry, 0, true, true, cx - rx, cy)) {
ctx.bezierCurveTo(seg[0], seg[1], seg[2], seg[3], seg[4], seg[5])
}
for (const seg of arcToCubics(cx - rx, cy, rx, ry, 0, true, true, cx + rx, cy)) {
ctx.bezierCurveTo(seg[0], seg[1], seg[2], seg[3], seg[4], seg[5])
}
ctx.closePath()
return true
}
case 'line': {
ctx.moveTo(num(el.getAttribute('x1'), 0), num(el.getAttribute('y1'), 0))
ctx.lineTo(num(el.getAttribute('x2'), 0), num(el.getAttribute('y2'), 0))
return true
}
case 'polyline':
case 'polygon': {
const points = (el.getAttribute('points') ?? '')
.split(/[\s,]+/)
.filter((piece) => piece !== '')
.map((piece) => Number.parseFloat(piece))
if (points.length < 4) return false
ctx.moveTo(points[0], points[1])
for (let i = 2; i + 1 < points.length; i += 2) ctx.lineTo(points[i], points[i + 1])
if (tag === 'polygon') ctx.closePath()
return true
}
default:
return false
}
}
function roundedRect(
ctx: PaintTarget,
x: number, y: number, w: number, h: number,
rx: number, ry: number,
): void {
ctx.moveTo(x + rx, y)
ctx.lineTo(x + w - rx, y)
ctx.quadraticCurveTo(x + w, y, x + w, y + ry)
ctx.lineTo(x + w, y + h - ry)
ctx.quadraticCurveTo(x + w, y + h, x + w - rx, y + h)
ctx.lineTo(x + rx, y + h)
ctx.quadraticCurveTo(x, y + h, x, y + h - ry)
ctx.lineTo(x, y + ry)
ctx.quadraticCurveTo(x, y, x + rx, y)
ctx.closePath()
}
function shape(el: Element, tag: string, ctx: PaintTarget, state: PaintState): void {
if (tag === 'text' || tag === 'tspan') {
paintText(el, ctx, state)
return
}
// A raster has no vector form, and nothing these figures draw is one.
if (tag === 'image' || tag === 'use' || tag === 'foreignobject') return
ctx.beginPath()
if (!outline(el, tag, ctx)) return
const gradient = state.fill === null ? null : state.fillGradient
if (gradient === null) {
fillAndStroke(ctx, state, false)
return
}
// A banded fill clips to the outline, so the stroke is laid along it again
// afterwards — in the order `paint-order` asks for, as for any other shape.
const fill = (): void => paintGradient(el, tag, ctx, state, gradient)
const stroke = (): void => {
ctx.beginPath()
outline(el, tag, ctx)
fillAndStroke(ctx, { ...state, fill: null }, false)
}
if (state.strokeFirst) {
stroke()
fill()
} else {
fill()
stroke()
}
}
/** How many bands a gradient's whole line is cut into, at most, between its first stop and its last. */
const GRADIENT_BANDS = 100
/**
* A shape filled with a linear gradient, as bands.
*
* Each band is a strip square to the gradient's line, clipped to the shape and
* filled with the colour the gradient has at the strip's middle: a hundred
* across the line, fewer where two stops are closer than a hundredth and one
* where two stops are the same colour, plus the first and last stops' colours
* padding out to the shape's edges, which is SVG's `spreadMethod="pad"`. An
* opaque band runs on into the next by half its width, since two strips that
* merely touch leave a hairline of the page between them in every
* anti-aliased reader; the next one covers the overlap.
*
* In `objectBoundingBox` units the line is in fractions of the shape's own box
* and so are the strips — square to the line *in that box*, as SVG has it,
* which on a box that is not square is a parallelogram on the page.
*/
function paintGradient(el: Element, tag: string, ctx: PaintTarget, state: PaintState, gradient: LinearPaint): void {
const bounds = boundsOf(el, tag)
if (bounds === null || gradient.stops.length === 0) return
// Gradient space → the shape's user space: the box's own affine for
// `objectBoundingBox`, the identity for `userSpaceOnUse`.
const boxed = gradient.units === 'objectBoundingBox'
const toUser = (x: number, y: number): [number, number] =>
boxed ? [bounds.x + x * bounds.width, bounds.y + y * bounds.height] : [x, y]
const corners: Array<[number, number]> = boxed
? [[0, 0], [1, 0], [1, 1], [0, 1]]
: [
[bounds.x, bounds.y],
[bounds.x + bounds.width, bounds.y],
[bounds.x + bounds.width, bounds.y + bounds.height],
[bounds.x, bounds.y + bounds.height],
]
const dx = gradient.x2 - gradient.x1
const dy = gradient.y2 - gradient.y1
const length2 = dx * dx + dy * dy
const stops = gradient.stops
const first = stops[0]
const last = stops[stops.length - 1]
const alpha = state.opacity * state.fillOpacity
const band = (from: number, to: number, rgb: [number, number, number], opacity: number): void => {
// A strip of the gradient's line from `from` to `to`, wide enough across
// to cover every corner of the shape.
const along = (t: number): [number, number] => [gradient.x1 + dx * t, gradient.y1 + dy * t]
const nx = -dy / Math.sqrt(length2)
const ny = dx / Math.sqrt(length2)
let reach = 0
for (const [cx, cy] of corners) {
reach = Math.max(reach, Math.abs((cx - gradient.x1) * nx + (cy - gradient.y1) * ny))
}
reach += 1
const [ax, ay] = along(from)
const [bx, by] = along(to)
const quad = [
toUser(ax + nx * reach, ay + ny * reach),
toUser(bx + nx * reach, by + ny * reach),
toUser(bx - nx * reach, by - ny * reach),
toUser(ax - nx * reach, ay - ny * reach),
]
ctx.globalAlpha = alpha * opacity
ctx.fillStyle = `rgb(${rgb.map((v) => Math.round(clamp01(v) * 255)).join(', ')})`
ctx.beginPath()
ctx.moveTo(quad[0][0], quad[0][1])
for (const [x, y] of quad.slice(1)) ctx.lineTo(x, y)
ctx.closePath()
ctx.fill()
}
ctx.save()
ctx.beginPath()
outline(el, tag, ctx)
ctx.clip()
if (!(length2 > 0)) {
// A line of no length paints the last stop everywhere, as SVG says.
band(-1, 1, last.rgb, last.opacity)
} else {
// Where the shape's corners fall on the line, so the padding reaches them.
let lo = 0
let hi = 1
for (const [cx, cy] of corners) {
const t = ((cx - gradient.x1) * dx + (cy - gradient.y1) * dy) / length2
lo = Math.min(lo, t)
hi = Math.max(hi, t)
}
type Strip = { from: number; to: number; rgb: [number, number, number]; opacity: number }
const strips: Strip[] = []
// Neighbours of one colour are one strip: a gradient of a hundred equal
// stops — the grey track behind a chart's colour bar — is one fill.
const push = (strip: Strip): void => {
const before = strips[strips.length - 1]
const same =
before !== undefined &&
before.opacity === strip.opacity &&
before.rgb.every((v, channel) => v === strip.rgb[channel])
if (same) before.to = strip.to
else strips.push(strip)
}
if (lo < first.offset) push({ from: lo - 0.01, to: first.offset, rgb: first.rgb, opacity: first.opacity })
for (let k = 0; k + 1 < stops.length; k++) {
const a = stops[k]
const b = stops[k + 1]
const span = b.offset - a.offset
if (!(span > 0)) continue
const same = a.opacity === b.opacity && a.rgb.every((v, channel) => v === b.rgb[channel])
const count = same ? 1 : Math.max(1, Math.round(span * GRADIENT_BANDS))
for (let i = 0; i < count; i++) {
const mid = (i + 0.5) / count
push({
from: a.offset + (span * i) / count,
to: a.offset + (span * (i + 1)) / count,
rgb: [0, 1, 2].map((channel) => a.rgb[channel] + (b.rgb[channel] - a.rgb[channel]) * mid) as [
number,
number,
number,
],
opacity: a.opacity + (b.opacity - a.opacity) * mid,
})
}
}
if (hi > last.offset) push({ from: last.offset, to: hi + 0.01, rgb: last.rgb, opacity: last.opacity })
strips.forEach((strip, index) => {
const opaque = alpha * strip.opacity >= 1 && index + 1 < strips.length
band(strip.from, opaque ? strip.to + (strip.to - strip.from) / 2 : strip.to, strip.rgb, strip.opacity)
})
}
ctx.restore()
ctx.globalAlpha = 1
}
/**
* A shape's box in its own user space, from the same outline it is drawn
* with: every point the outline visits, a curve's handles included. That is
* the box a little generously for a curve that does not reach its handles,
* which on the shapes a chart fills with a gradient — rectangles and polygons
* — is the box exactly.
*/
function boundsOf(el: Element, tag: string): { x: number; y: number; width: number; height: number } | null {
let x0 = Infinity
let y0 = Infinity
let x1 = -Infinity
let y1 = -Infinity
const add = (x: number, y: number): void => {
x0 = Math.min(x0, x)
y0 = Math.min(y0, y)
x1 = Math.max(x1, x)
y1 = Math.max(y1, y)
}
const noop = (): void => {}
const recorder = {
beginPath: noop,
closePath: noop,
moveTo: add,
lineTo: add,
rect: (x: number, y: number, w: number, h: number) => {
add(x, y)
add(x + w, y + h)
},
arc: (x: number, y: number, r: number) => {
add(x - r, y - r)
add(x + r, y + r)
},
bezierCurveTo: (a: number, b: number, c: number, d: number, e: number, f: number) => {
add(a, b)
add(c, d)
add(e, f)
},
quadraticCurveTo: (a: number, b: number, c: number, d: number) => {
add(a, b)
add(c, d)
},
}
if (!outline(el, tag, recorder as unknown as PaintTarget)) return null
if (!(x1 > x0) || !(y1 > y0)) return null
return { x: x0, y: y0, width: x1 - x0, height: y1 - y0 }
}
/**
* Lay down the fill and the stroke, in the order `paint-order` asks for.
*
* `globalAlpha` carries both the element's own opacity and the per-paint one,
* because that is the only transparency the target has — and it is enough:
* SVG's two opacities multiply into exactly this number for a shape painted on
* its own, which every shape here is.
*/
function fillAndStroke(ctx: PaintTarget, state: PaintState, text: boolean): void {
const strokes = state.stroke !== null && state.strokeWidth > 0
const paintFill = (): void => {
if (state.fill === null) return
ctx.globalAlpha = state.opacity * state.fillOpacity
ctx.fillStyle = state.fill
if (!text) ctx.fill()
}
const paintStroke = (): void => {
if (!strokes) return
ctx.globalAlpha = state.opacity * state.strokeOpacity
ctx.strokeStyle = state.stroke as string
ctx.lineWidth = state.strokeWidth
ctx.lineJoin = state.lineJoin
ctx.lineCap = state.lineCap
ctx.setLineDash(state.dash)
if (!text) ctx.stroke()
}
if (state.strokeFirst) {
paintStroke()
paintFill()
} else {
paintFill()
paintStroke()
}
ctx.globalAlpha = 1
ctx.setLineDash([])
}
/**
* One run of text.
*
* `x`/`y` are the SVG anchor, and `text-anchor`/`dominant-baseline` have already
* become the canvas's `textAlign`/`textBaseline`, so the context places the run
* itself — which matters for the export, where the offsets are worked out from
* the screen font's metrics rather than guessed.
*
* A stroked run is `zrender`'s halo, kept because a label over a busy series is
* unreadable without it; `paint-order` decides which way round the two go.
*/
function paintText(el: Element, ctx: PaintTarget, state: PaintState): void {
const spans = Array.from(el.children).filter(
(child) => child.tagName.toLowerCase() === 'tspan',
)
const text = spans.length > 0 ? '' : (el.textContent ?? '')
if (text.trim() !== '') {
const x = num(el.getAttribute('x'), 0) + num(el.getAttribute('dx'), 0)
const y = num(el.getAttribute('y'), 0) + num(el.getAttribute('dy'), 0)
ctx.font = fontOf(state)
ctx.textAlign = state.anchor
ctx.textBaseline = state.baseline
const strokes = state.stroke !== null && state.strokeWidth > 0
const write = (): void => {
if (state.fill === null) return
ctx.globalAlpha = state.opacity * state.fillOpacity
ctx.fillStyle = state.fill
ctx.fillText(text, x, y)
}
const halo = (): void => {
if (!strokes) return
ctx.globalAlpha = state.opacity * state.strokeOpacity
ctx.strokeStyle = state.stroke as string
ctx.lineWidth = state.strokeWidth
ctx.lineJoin = state.lineJoin
ctx.setLineDash([])
ctx.strokeText(text, x, y)
}
if (state.strokeFirst) {
halo()
write()
} else {
write()
halo()
}
ctx.globalAlpha = 1
}
for (const span of spans) paintText(span, ctx, descend(span, state, new Map()))
}
/** A CSS `font` shorthand out of the resolved text state. */
function fontOf(state: PaintState): string {
const style = state.fontStyle !== 'normal' ? `${state.fontStyle} ` : ''
const weight = state.fontWeight !== 'normal' ? `${state.fontWeight} ` : ''
return `${style}${weight}${state.fontSize}px ${state.fontFamily}`
}
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