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* A structure drawn through a `CanvasRenderingContext2D`, for the figure (§25).
*
* Every representation is paths, and paths are what the vector export is made
* of (`ui/vector.ts`): five thousand beads are five thousand `arc`s, which is
* squarely on the side of the line `ui/analysisPlots.ts` draws between *tens of
* cells are paths* and *twelve thousand bins are pixels*. Beads are discs and
* sticks are segments. The **tube** is a stretch per bead along the curve the
* GPU draws it on, filled band by band from its shadowed rim to its highlight.
* It used to be handed back to the
* GPU as a raster, on the argument that a lit surface is not a path; so the
* default representation of every model left as a picture of pixels in the one
* file that was supposed to be a drawing (§25.7). A contact map's cells are now
* the only raster any PDF of this application carries.
*
* It is **not a second renderer**. The scene, the camera, the colours and what
* is lit are the same objects the adapter is handed, projected through the
* same arithmetic (`structure/camera.ts`), and everything the adapter adds to
* the model — the dashes across a gap, the ruler's ticks, the centre of
* rotation, the depth slab and the fog — is drawn here from the same numbers,
* so the page shows the picture the screen showed. The words written on the
* model are one function, {@link drawStructureLabels}, which the adapter's own
* snapshot calls too: the PNG and the PDF cannot disagree about a name. It is
* also the one path a test can exercise without a GPU: `drawingOf` runs this
* into a `VectorPage`, and a figure that draws nothing is caught by the
* operator stream being empty.
*
* Painter's algorithm: every mark is sorted by depth and drawn far to near, so
* a bead in front covers a bead behind. Exact for discs of one radius, and the
* right picture for sticks and a tube at the widths a figure uses.
*
* **Lit, as the screen is.** A model drawn in flat colour reads as a tangle of
* ribbons on paper beside the PNG of the same model, which reads as a solid.
* So every surface is shaded by the screen's own key light ({@link KEY}, which
* rides with the eye): a bead is a **radial shading** from its highlight out to
* its shadowed rim — `createRadialGradient`, which the page writes as a PDF
* shading, smooth at any zoom — and a tube or a stick, which no gradient can
* follow round a curve, is a stack of strokes, each narrower, lighter and
* nudged towards the light, fine enough that the steps are under a third of a
* pixel. The depth cue is the screen's fog besides, done by mixing every
* colour — each of a bead's stops — towards the paper, and beads and sticks
* further from the eye are drawn a little smaller.
*/
import type { StructureStyle } from '../annotations/types'
import { fmt } from '../units'
import { basis, frameAxes, project, type Camera } from './camera'
import type { BeadColours } from './colour'
import { parseColour, UNSET_COLOUR } from './colour'
import { centroidOf, distanceBetween, type Structure } from './scene'
/** Everything the painter draws from — the same object the adapter is handed. */
export interface StructureView {
structure: Structure
camera: Camera
style: StructureStyle
colours: BeadColours
/**
* `1` for a bead inside the deck's window, `0` for one outside it; `null`
* where nothing is windowed and every bead is lit.
*/
lit: Uint8Array | null
/** Beads under the pointer, or lit by an echo from another panel. */
hovered: readonly number[]
/** The pinned bead, or `-1`. */
pinned: number
/** Two beads joined by a chord — the two ends of a hovered contact. */
chord: readonly [number, number] | null
/** Loops drawn as chords (§25.5): each pair's anchors, as beads. */
chords: ReadonlyArray<readonly [number, number]>
/** The reader's measurements: pairs of beads joined by a dashed line, with the distance written at the middle. */
measures: ReadonlyArray<readonly [number, number]>
/**
* The reader's marked places (§25.4): a bead drawn in the mark's own colour
* at {@link MARKED_BEAD} times the radius, so a place stands out of the
* fibre it is on whether or not anything else is coloured by the marks.
*
* Places only. A loop is two places and a chord, and it is the chord that
* says *these two*; two fat beads at its ends would be a third way of
* saying what the chord and the colouring already do.
*/
marks: ReadonlyArray<{ bead: number; colour: string }>
/** The genomic ruler: beads that carry a tick, and what the tick says. */
ruler: ReadonlyArray<{ bead: number; label: string }>
/**
* The reader's bookmarks (§25.5), as the bead in the middle of each and its
* name — written on the model with the sequence names, under the same
* switch. Optional: a view built with no session behind it has none.
*/
bookmarks?: ReadonlyArray<{ bead: number; label: string }>
/** Another model in this one's frame (`StructureStyle.compare`), or `null`. */
overlay: { structure: Structure; colours: BeadColours } | null
/** The one haplotype shown, as an index, or `-1` for all of them. */
haplotype: number
}
/** What the figure is drawn in, read off the page it is drawn on. */
export interface PainterPalette {
background: string
ink: string
halo: string
}
/** How much smaller the farthest bead and stick are drawn than the nearest. */
const DEPTH_SHRINK = 0.35
/** The opacity of a bead outside the window, under `others: 'ghost'`, where a style says nothing. */
export const GHOST_OPACITY = 0.15
/** Below this an alpha is *gone*, as the adapter's `GHOST_GONE` has it: nothing is drawn. */
const GHOST_GONE = 0.004
/** How much wider than a bead the halo round a hovered or pinned one is. */
const HALO = 1.8
/** How much wider than a bead a marked place is drawn: twice, which is four times the ink. */
export const MARKED_BEAD = 2
/** Ink drawn along or across the fibre — a gap's dashes, a loop's chord — as a share of a stick's width. */
const INK_SHARE = 0.5
/**
* The screen's lights, in the camera's frame — x to the right, y up, z towards
* the reader — where `structure/three.ts` puts them, riding with the eye: a key
* above and to the right in front, a weaker fill below and to the left behind,
* and ambient. The weights are the screen's balance read off its PNG rather
* than its physics: the face towards the reader is the surface's own colour, a
* highlight up and to the right, the silhouette away from the key in shadow.
*/
const KEY = unit([1, 1.2, 1.5])
const FILL = unit([-1, -0.4, -1])
const AMBIENT = 0.55
const KEY_WEIGHT = 0.6
const FILL_WEIGHT = 0.25
/** The specular highlight: how far towards white at its peak, and how tight it is. */
const SPECULAR = 0.35
const SHININESS = 24
/** Halfway between the key and the eye: where on a sphere the highlight sits. */
const HIGHLIGHT = unit([KEY[0], KEY[1], KEY[2] + 1])
/** How many stops a bead's shading carries, from its highlight to its rim. */
const SPHERE_STOPS = 12
/**
* Below this many pixels across, a tube, a stick or a bead is flat. Low, since
* the page is a drawing: a tube a pixel across on the screen's framing is a
* reader's zoom away from being the width of a finger, and lit when it is.
*/
const TUBE_SHADED_MIN = 0.75
/** The widest a tube's band of shading is, in pixels, and the fewest and most bands one carries. */
const BAND_WIDTH = 0.3
const BANDS_MIN = 8
const BANDS_MAX = 32
/** How many bands further in a tube's band reaches under the ones over it (see {@link tubeMarks}). */
const RING_REACH = 3
/** The longest straight piece a tube's outline is drawn in, in pixels. */
const OUTLINE_STEP = 1.5
/**
* How far, in CSS pixels, an opaque stretch of tube runs on past the midpoint
* where it meets the next — see {@link tubeMarks}. Not for a ghosted one,
* whose overlap would be a band of twice the alpha at every joint.
*/
const JOIN_OVERLAP = 0.5
/** The compared model's tube, as a share of this one's: thinner, so the two read apart where they cross. */
const OVERLAY_TUBE = 0.7
/** The centre of rotation's parts, as the adapter builds them, in units of its size (`structure/three.ts`). */
const CENTRE = {
/** The whole gizmo, as a share of the camera's distance. */
size: 0.12,
ball: 0.075,
shaft: { from: 0, to: 0.8, radius: 0.022 },
head: { from: 0.8, to: 1.02, radius: 0.07 },
stub: { from: 0, to: -0.45, radius: 0.012 },
/** x red, y green, z blue — the colours every 3D tool uses. */
colours: ['#d8453c', '#2f9e44', '#3b7ddd'],
ballOpacity: 0.8,
armOpacity: 0.95,
} as const
type Rgb = [number, number, number]
/** One thing on the model, at the depth it is sorted by. */
interface Mark {
depth: number
/**
* Which of several marks at one depth goes first: a halo under its bead, the
* fibre under the bead on it, a ruler's tick over both.
*/
layer: number
draw: () => void
}
/** Where a set of beads lands on the page, and which of them are drawn at all. */
interface Placed {
px: Float64Array
py: Float64Array
depth: Float64Array
/** Pixels per scene unit at the bead's depth. */
size: Float64Array
/** `1` for a bead that is drawn: placed, of the haplotype shown, not hidden, inside the slab. */
drawn: Uint8Array
}
/**
* Draw the view into a box.
*
* The context is asked for nothing outside `VectorTarget`'s subset: `arc`,
* `moveTo`, `lineTo`, `bezierCurveTo`, `fill`, `stroke`, `setLineDash`,
* `fillText` and the colour and width properties. That is the whole of the
* contract with the PDF.
*/
export function drawStructure(
ctx: CanvasRenderingContext2D,
box: { width: number; height: number },
view: StructureView,
palette: PainterPalette,
): void {
const { structure, camera, style } = view
ctx.save()
ctx.fillStyle = palette.background
ctx.fillRect(0, 0, box.width, box.height)
// The depth slab, as the adapter's two clipping planes: what lies further
// than `half` either side of the centre of rotation, along the line of
// sight, is not drawn.
const half = slabHalf(structure, style)
const inSlab = slabTest(camera, style, half)
const placed = placeAll(structure, camera, box, inSlab, (i) => visible(view, i))
const { px, py, depth, size, drawn } = placed
let nearest = Infinity
let farthest = -Infinity
for (let i = 0; i < drawn.length; i++) {
if (drawn[i] === 0) continue
if (depth[i] < nearest) nearest = depth[i]
if (depth[i] > farthest) farthest = depth[i]
}
const span = farthest > nearest ? farthest - nearest : 1
/** How far back a bead is, 0 at the nearest and 1 at the farthest: the shrink. */
const back = (i: number): number => (depth[i] - nearest) / span
const fog = fogAt(camera, style, half)
const background = parseColour(palette.background)
const ink = parseColour(palette.ink)
const alphaOf = (i: number): number => (view.lit !== null && view.lit[i] === 0 ? style.opacity : 1)
const rgbOf = (colours: BeadColours, i: number): Rgb => [
colours.rgb[i * 3],
colours.rgb[i * 3 + 1],
colours.rgb[i * 3 + 2],
]
/** A colour as it reads at a depth: mixed towards the paper by the fog. */
const fogged = (rgb: Rgb, at: number): string => css(mix(rgb, background, fog(at)))
const beadRadius = structure.step * style.beadRadius
const stickRadius = structure.step * style.tubeRadius
ctx.lineCap = 'round'
ctx.lineJoin = 'round'
// Every mark with its depth, then one sort. Far to near is what makes near
// cover far; the layer orders marks at the same depth.
const marks: Mark[] = []
// The compared model, in this one's frame: a thinner tube in its own
// colours, sorted in with this model's marks, since the two are one scene.
const overlay = view.overlay
if (overlay !== null) {
const o = overlay.structure
const there = placeAll(o, camera, box, inSlab, (i) => o.present[i] === 1)
for (const chain of o.chains) {
tubeMarks(ctx, marks, chain, there, {
radius: stickRadius * OVERLAY_TUBE,
colour: (i) => rgbOf(overlay.colours, i),
alpha: () => 1,
fogged,
position: (i) => [o.x[i], o.y[i], o.z[i]],
camera,
box,
})
}
}
if (style.tube) {
for (const chain of structure.chains) {
if (view.haplotype >= 0 && chain.hap !== view.haplotype) continue
tubeMarks(ctx, marks, chain, placed, {
radius: stickRadius,
colour: (i) => rgbOf(view.colours, i),
alpha: alphaOf,
fogged,
position: (i) => [structure.x[i], structure.y[i], structure.z[i]],
camera,
box,
})
}
}
if (style.sticks) {
for (const chain of structure.chains) {
if (view.haplotype >= 0 && chain.hap !== view.haplotype) continue
for (let r = 0; r < chain.runs.length; r += 2) {
for (let k = chain.runs[r] + 1; k < chain.runs[r + 1]; k++) {
const a = chain.beads[k - 1]
const b = chain.beads[k]
if (drawn[a] === 0 || drawn[b] === 0) continue
marks.push({
// Under both its beads where they are drawn: a stick runs between
// their centres, inside both spheres, and sorted at its middle it
// was laid over the farther one — invisible while both were one
// flat colour, a dark bar across a lit sphere once they are not.
depth: style.beads ? Math.max(depth[a], depth[b]) : (depth[a] + depth[b]) / 2,
layer: 1,
draw: () => {
const alpha = (alphaOf(a) + alphaOf(b)) / 2
if (alpha < GHOST_GONE) return
const t = (back(a) + back(b)) / 2
const width = Math.max(0.5, stickRadius * 2 * ((size[a] + size[b]) / 2) * (1 - DEPTH_SHRINK * t))
ctx.globalAlpha = alpha
ctx.setLineDash([])
// Two-tone sticks, each half in its own bead's colour, so a
// colouring by position or by a track reads along the fibre
// rather than in steps — and lit, band by band, both halves'
// band before either's next, so neither half's cap is laid
// across the other's lighter core.
const mx = (px[a] + px[b]) / 2
const my = (py[a] + py[b]) / 2
for (const band of bandsOf(width, alpha)) {
const [dx, dy] = nudgeOf(width, band.outer)
ctx.lineWidth = width * band.outer
ctx.strokeStyle = fogged(band.shade(rgbOf(view.colours, a)), depth[a])
ctx.beginPath()
ctx.moveTo(px[a] + dx, py[a] + dy)
ctx.lineTo(mx + dx, my + dy)
ctx.stroke()
ctx.strokeStyle = fogged(band.shade(rgbOf(view.colours, b)), depth[b])
ctx.beginPath()
ctx.moveTo(mx + dx, my + dy)
ctx.lineTo(px[b] + dx, py[b] + dy)
ctx.stroke()
}
},
})
}
}
}
}
// A dashed run across each gap, **whatever the model is drawn as**: a gap is
// a fact about the model, and a chain that seems to end where a bead is
// missing is a model that looks like two. The dashes are the adapter's, in
// the model's own units and projected one by one, so a gap seen end-on is
// short dashes rather than the same pattern laid flat.
for (const chain of structure.chains) {
if (view.haplotype >= 0 && chain.hap !== view.haplotype) continue
for (let r = 2; r < chain.runs.length; r += 2) {
const a = chain.beads[chain.runs[r - 1] - 1]
const b = chain.beads[chain.runs[r]]
if (drawn[a] === 0 || drawn[b] === 0) continue
const dashes = dashesBetween(camera, box, structure, a, b, stickRadius * 3, stickRadius * 2)
const at = (depth[a] + depth[b]) / 2
marks.push({
depth: at,
layer: 1,
draw: () => {
const alpha = (alphaOf(a) + alphaOf(b)) / 2
if (alpha < GHOST_GONE) return
ctx.globalAlpha = alpha
ctx.strokeStyle = fogged(ink, at)
// Ink at half the stick's width: the line says *nothing is here*,
// and a line about the fibre that outweighs the fibre reads as part
// of it.
ctx.lineWidth = Math.max(1, stickRadius * 2 * INK_SHARE * ((size[a] + size[b]) / 2))
ctx.lineCap = 'butt'
ctx.setLineDash([])
ctx.beginPath()
for (const [x0, y0, x1, y1] of dashes) {
ctx.moveTo(x0, y0)
ctx.lineTo(x1, y1)
}
ctx.stroke()
ctx.lineCap = 'round'
},
})
}
}
// The halo behind a hovered or pinned bead, under whatever is drawn there:
// round the bead, or round the fibre where there are no beads.
const haloRadius = HALO * (style.beads ? beadRadius : Math.max(stickRadius, beadRadius * 0.6))
for (const i of new Set([...view.hovered, ...(view.pinned >= 0 ? [view.pinned] : [])])) {
if (i < 0 || i >= drawn.length || drawn[i] === 0) continue
marks.push({
depth: depth[i],
layer: 0,
draw: () => {
const t = back(i)
ctx.globalAlpha = 1
ctx.fillStyle = palette.ink
ctx.beginPath()
ctx.arc(px[i], py[i], Math.max(1, haloRadius * size[i] * (1 - DEPTH_SHRINK * t)), 0, Math.PI * 2)
ctx.fill()
},
})
}
if (style.beads) {
for (let i = 0; i < drawn.length; i++) {
if (drawn[i] === 0) continue
marks.push({
depth: depth[i],
layer: 2,
draw: () => {
const alpha = alphaOf(i)
if (alpha < GHOST_GONE) return
const t = back(i)
const radius = Math.max(0.4, beadRadius * size[i] * (1 - DEPTH_SHRINK * t))
ctx.globalAlpha = alpha
ctx.fillStyle = sphereFill(ctx, px[i], py[i], radius, rgbOf(view.colours, i), (rgb) => fogged(rgb, depth[i]))
ctx.beginPath()
ctx.arc(px[i], py[i], radius, 0, Math.PI * 2)
ctx.fill()
},
})
}
}
// The ruler's ticks: a small bead of ink at each, over the fibre it marks,
// faded with the bead it sits on as every mark is (§25.5).
const tickRadius = Math.max(stickRadius * 1.6, beadRadius * 0.8)
for (const tick of view.ruler) {
const i = tick.bead
if (i < 0 || i >= drawn.length || drawn[i] === 0) continue
marks.push({
depth: depth[i],
layer: 3,
draw: () => {
const alpha = alphaOf(i)
if (alpha < GHOST_GONE) return
ctx.globalAlpha = alpha
ctx.fillStyle = fogged(ink, depth[i])
ctx.beginPath()
ctx.arc(px[i], py[i], Math.max(0.8, tickRadius * size[i]), 0, Math.PI * 2)
ctx.fill()
},
})
}
marks.sort((m, o) => o.depth - m.depth || m.layer - o.layer)
for (const mark of marks) mark.draw()
ctx.setLineDash([])
ctx.lineCap = 'round'
// The reader's marked places: the bead again, twice the size, in the mark's
// own colour. Over the fibre and under every line, so a marked place reads
// as a place on the model rather than as another line across it.
for (const mark of view.marks) {
const i = mark.bead
if (i < 0 || i >= drawn.length || drawn[i] === 0) continue
const alpha = alphaOf(i)
if (alpha < GHOST_GONE) continue
const t = back(i)
const radius = Math.max(0.8, beadRadius * size[i] * MARKED_BEAD * (1 - DEPTH_SHRINK * t))
ctx.globalAlpha = alpha
ctx.fillStyle = sphereFill(ctx, px[i], py[i], radius, parseColour(mark.colour), (rgb) => fogged(rgb, depth[i]))
ctx.beginPath()
ctx.arc(px[i], py[i], radius, 0, Math.PI * 2)
ctx.fill()
}
// Loops as chords, under the hovered one: thin, so a hundred of them read
// as a texture of the model rather than a cage round it.
if (view.chords.length > 0 && style.chords) {
ctx.globalAlpha = 0.9
ctx.strokeStyle = palette.ink
ctx.beginPath()
let widest = 0
for (const [a, b] of view.chords) {
if (drawn[a] !== 1 || drawn[b] !== 1) continue
widest = Math.max(widest, size[a], size[b])
ctx.moveTo(px[a], py[a])
ctx.lineTo(px[b], py[b])
}
ctx.lineWidth = Math.max(1, stickRadius * 2 * INK_SHARE * widest)
ctx.stroke()
}
// The reader's measurements: dashed ink, the dashes the adapter's. The
// distance is written with the other words, below.
for (const [a, b] of view.measures) {
if (drawn[a] !== 1 || drawn[b] !== 1) continue
ctx.globalAlpha = 1
ctx.strokeStyle = palette.ink
ctx.lineWidth = Math.max(1.2, stickRadius * 1.2 * ((size[a] + size[b]) / 2))
ctx.lineCap = 'butt'
ctx.beginPath()
for (const [x0, y0, x1, y1] of dashesBetween(camera, box, structure, a, b, stickRadius * 2.5, stickRadius * 1.5)) {
ctx.moveTo(x0, y0)
ctx.lineTo(x1, y1)
}
ctx.stroke()
ctx.lineCap = 'round'
}
// The chord on top of everything: the one line that says *these two*.
if (view.chord !== null) {
const [a, b] = view.chord
if (drawn[a] === 1 && drawn[b] === 1) {
ctx.globalAlpha = 1
ctx.strokeStyle = palette.ink
ctx.lineWidth = Math.max(2, stickRadius * 1.6 * ((size[a] + size[b]) / 2))
ctx.lineCap = 'butt'
ctx.beginPath()
for (const [x0, y0, x1, y1] of dashesBetween(camera, box, structure, a, b, stickRadius * 3, stickRadius * 2)) {
ctx.moveTo(x0, y0)
ctx.lineTo(x1, y1)
}
ctx.stroke()
ctx.lineCap = 'round'
}
}
// The centre of rotation, over the model as the adapter draws it — a centre
// inside a tube is still the centre.
if (style.axes) drawCentre(ctx, box, view, palette)
ctx.globalAlpha = 1
drawStructureLabels(ctx, box, view, palette)
ctx.restore()
}
/**
* Everything written on the model — the ruler's labels, the measurements'
* distances, and under *names* the bookmarks and each chain's name — in the
* box's own CSS pixels.
*
* One function for both pictures: the vector page calls it above, and the
* adapter's snapshot calls it over the GL frame (`structure/three.ts`), so the
* PNG and the PDF of one model carry the same words in the same places. What
* the cell writes as DOM over its canvas is the source: a tick's label is
* every *k*-th of at most eighty, a sequence outside the window under *hide*
* is not named, and one ghosted is named faintly.
*
* Not clipped by the depth slab, as the cell's own labels are not.
*/
export function drawStructureLabels(
ctx: CanvasRenderingContext2D,
box: { width: number; height: number },
view: StructureView,
palette: PainterPalette,
): void {
const { structure, style } = view
const named = (bead: number): boolean =>
bead >= 0 &&
bead < structure.present.length &&
structure.present[bead] === 1 &&
!(view.haplotype >= 0 && structure.model.hap[bead] !== view.haplotype) &&
!(view.lit !== null && view.lit[bead] === 0 && style.others === 'hide')
const at = (bead: number): { px: number; py: number } | null =>
project(view.camera, box, structure.x[bead], structure.y[bead], structure.z[bead])
/** A run of text with the halo under it, offset as the figure's names always were. */
const write = (text: string, x: number, y: number): void => {
ctx.fillStyle = palette.halo
ctx.fillText(text, x + 1, y + 1)
ctx.fillStyle = palette.ink
ctx.fillText(text, x, y)
}
ctx.save()
ctx.setLineDash([])
// The ruler's labels beside their ticks, every k-th where there are more
// than eighty, so a whole genome is not a cloud of numbers.
if (view.ruler.length > 0) {
const every = Math.max(1, Math.ceil(view.ruler.length / 80))
ctx.font = '10px sans-serif'
ctx.textAlign = 'left'
ctx.textBaseline = 'middle'
ctx.globalAlpha = 0.8
view.ruler.forEach((tick, index) => {
if (index % every !== 0 || !named(tick.bead)) return
const point = at(tick.bead)
if (point !== null) write(tick.label, point.px + 6, point.py)
})
}
// The measurements' distances, at the middle of each line, in the file's
// own units — the number the card and the cell print.
if (view.measures.length > 0) {
ctx.font = '600 10px sans-serif'
ctx.textAlign = 'center'
ctx.textBaseline = 'bottom'
ctx.globalAlpha = 1
for (const [a, b] of view.measures) {
if (!named(a) || !named(b)) continue
const pa = at(a)
const pb = at(b)
if (pa === null || pb === null) continue
write(fmt.num(distanceBetween(structure, a, b)), (pa.px + pb.px) / 2, (pa.py + pb.py) / 2 - 3)
}
}
if (style.labels) {
ctx.font = '11px sans-serif'
ctx.textAlign = 'center'
ctx.textBaseline = 'middle'
// The reader's bookmarks, at the bead in the middle of each (§25.5).
for (const bookmark of view.bookmarks ?? []) {
if (!named(bookmark.bead)) continue
const point = at(bookmark.bead)
if (point === null) continue
ctx.globalAlpha = view.lit !== null && view.lit[bookmark.bead] === 0 ? 0.45 : 1
write(bookmark.label, point.px, point.py)
}
// Chain names at each chain's midpoint bead.
for (const chain of structure.chains) {
if (view.haplotype >= 0 && chain.hap !== view.haplotype) continue
const mid = chain.beads[chain.beads.length >> 1]
if (mid === undefined || !named(mid)) continue
const point = at(mid)
if (point === null) continue
const name = structure.contigs[chain.contig]
const label =
structure.haplotypes.length > 1 && view.haplotype < 0
? `${name} ${structure.haplotypes[chain.hap]}`
: name
ctx.globalAlpha = view.lit !== null && view.lit[mid] === 0 ? 0.45 : 1
write(label, point.px, point.py)
}
}
ctx.restore()
}
/**
* One chain's tube, as a mark per bead.
*
* **Per bead, not per segment, and that is what makes it read as one tube.**
* The obvious drawing is a round-capped stroke between each pair of
* neighbours, sorted by depth — and every one of them then lays its dark rim's
* cap over the light core of the neighbour drawn before it, so the fibre comes
* out as a string of sausages with a dark crescent at every bead. Here each
* bead owns the stretch from half way to its previous neighbour to half way to
* its next, which is exactly the stretch the adapter colours by that bead, and
* the stretches meet **butt to butt** at those midpoints, where the two have
* one tangent: no rim is ever laid across another stretch's core, and a bead
* in front still covers a bead behind where the fibre crosses itself. Each
* runs on {@link JOIN_OVERLAP} past its midpoints, straight along the tangent,
* because two shapes that merely touch leave a hairline of the paper between
* them in every anti-aliased reader; whichever of the two is drawn second
* covers the overlap with its own rim *and* core, so the joint shows nothing.
*
* **On the curve the adapter draws.** The tube on screen is a Catmull–Rom
* spline through the beads (`CatmullRomCurve3` at a tension of a half), whose
* every span is a cubic Bézier — and an orthographic projection of a Bézier is
* the Bézier of the projected control points, which `bezierCurveTo` draws
* exactly. A run's two ends are given the curve's own reflected neighbour, and
* a round end, since the stretch's own cap has to be butt where it meets the
* next.
*
* Each stretch is lit as a cylinder is ({@link bandsOf}): a stack of bands
* along the one curve, from the full width in shadow to a narrow highlight,
* each nudged towards the key light. A band is filled, not stroked, as the
* outline of the curve offset either side ({@link ribbon}), so its width can
* run from one midpoint's to the other's. A ghosted bead, or a tube too thin
* to shade, is one flat band at the bead's alpha, as the adapter draws it at
* one.
*/
function tubeMarks(
ctx: CanvasRenderingContext2D,
marks: Mark[],
chain: { beads: Int32Array; runs: Int32Array },
placed: Placed,
options: {
radius: number
colour: (i: number) => Rgb
alpha: (i: number) => number
fogged: (rgb: Rgb, depth: number) => string
position: (i: number) => [number, number, number]
camera: Camera
box: { width: number; height: number }
},
): void {
const { drawn, depth, size, px, py } = placed
for (let r = 0; r < chain.runs.length; r += 2) {
// The run split wherever a bead is not drawn — hidden by the window, or
// cut by the slab — since a tube is never drawn through what is not there.
let run: number[] = []
const flush = (): void => {
if (run.length >= 2) tubeRun(run)
run = []
}
for (let k = chain.runs[r]; k < chain.runs[r + 1]; k++) {
const bead = chain.beads[k]
if (drawn[bead] === 1) run.push(bead)
else flush()
}
flush()
}
function tubeRun(beads: number[]): void {
const count = beads.length
// Each span's Bézier, projected, and split in two at its middle — the two
// halves belong to the beads at its two ends.
const firsts: number[][] = []
const seconds: number[][] = []
for (let s = 0; s + 1 < count; s++) {
const a = options.position(beads[s])
const b = options.position(beads[s + 1])
const before = s > 0 ? options.position(beads[s - 1]) : reflect(a, b)
const after = s + 2 < count ? options.position(beads[s + 2]) : reflect(b, a)
const c1 = a.map((v, axis) => v + (b[axis] - before[axis]) / 6)
const c2 = b.map((v, axis) => v - (after[axis] - a[axis]) / 6)
const flat = [a, c1, c2, b].map((point) => {
const at = project(options.camera, options.box, point[0], point[1], point[2])
return at === null ? [Number.NaN, Number.NaN] : [at.px, at.py]
})
const [first, second] = splitBezier(flat)
firsts.push(first)
seconds.push(second)
}
for (let j = 0; j < count; j++) {
const bead = beads[j]
const into = j > 0 ? seconds[j - 1] : null
const out = j + 1 < count ? firsts[j] : null
if ([...(into ?? []), ...(out ?? [])].some((v) => !Number.isFinite(v))) continue
const end = into === null || out === null
// The direction the curve leaves each midpoint in, for the overlap.
const back = into === null ? null : towards(into, 0)
const on = out === null ? null : towards(out, 6)
marks.push({
depth: depth[bead],
layer: 1,
draw: () => {
const alpha = options.alpha(bead)
if (alpha < GHOST_GONE) return
const colour = options.colour(bead)
const widthOf = (b: number): number => Math.max(0.5, options.radius * 2 * size[b])
const width = widthOf(bead)
// The width at each midpoint is the two beads' mean, from either
// side, so two stretches meet at one width rather than a step of
// the perspective between them.
const before = j > 0 ? (width + widthOf(beads[j - 1])) / 2 : width
const after = j + 1 < count ? (width + widthOf(beads[j + 1])) / 2 : width
const overlap = alpha >= 1 ? JOIN_OVERLAP : 0
const line = centreline(into, out, back, on, [px[bead], py[bead]], before, width, after, overlap)
const bands = bandsOf(width, alpha)
ctx.globalAlpha = alpha
ctx.setLineDash([])
for (let k = 0; k < bands.length; k++) {
const band = bands[k]
ctx.fillStyle = options.fogged(band.shade(colour), depth[bead])
// A round end where the run stops: a disc per band.
if (end) {
const [dx, dy] = nudgeOf(width, band.outer)
ctx.beginPath()
ctx.arc(px[bead] + dx, py[bead] + dy, (width * band.outer) / 2, 0, Math.PI * 2)
ctx.fill()
}
// Each band is the ring of the section that is its own, and
// reaches only RING_REACH bands in under the next: so where this
// stretch is laid over its neighbour's end, every part of it lies
// on the neighbour's same band, and nothing shows the seam. A band
// laid whole over the lighter ones of the stretch below put the
// edge of every band at one line, and the reader's anti-aliasing
// left a dark hairline across the tube at every bead.
const inner = k + RING_REACH < bands.length ? bands[k + RING_REACH].outer : null
ctx.beginPath()
ribbon(ctx, line, band.outer, inner, 1)
ribbon(ctx, line, band.outer, inner, -1)
ctx.fill()
}
ctx.lineCap = 'round'
},
})
}
}
}
/**
* The unit tangent of a projected half-span `[x0, y0, c1x, c1y, c2x, c2y, x1,
* y1]` at one of its ends — `0` its start, pointing into it, or `6` its end,
* pointing out of it — falling back along the control points where two of
* them coincide.
*/
function towards(half: number[], at: 0 | 6): [number, number] {
const order = at === 0 ? [2, 4, 6] : [4, 2, 0]
for (const other of order) {
const dx = at === 0 ? half[other] - half[0] : half[6] - half[other]
const dy = at === 0 ? half[other + 1] - half[1] : half[7] - half[other + 1]
const length = Math.hypot(dx, dy)
if (length > 1e-9) return [dx / length, dy / length]
}
return [0, 0]
}
/** The point the far side of `a` from `b`: the curve's own neighbour at a run's end. */
function reflect(a: [number, number, number], b: [number, number, number]): [number, number, number] {
return [2 * a[0] - b[0], 2 * a[1] - b[1], 2 * a[2] - b[2]]
}
/**
* A cubic Bézier split at its middle (de Casteljau), each half as
* `[x0, y0, c1x, c1y, c2x, c2y, x1, y1]`.
*/
function splitBezier(points: number[][]): [number[], number[]] {
const [p0, p1, p2, p3] = points
const mid = (a: number[], b: number[]): number[] => [(a[0] + b[0]) / 2, (a[1] + b[1]) / 2]
const m01 = mid(p0, p1)
const m12 = mid(p1, p2)
const m23 = mid(p2, p3)
const m012 = mid(m01, m12)
const m123 = mid(m12, m23)
const s = mid(m012, m123)
return [
[...p0, ...m01, ...m012, ...s],
[...s, ...m123, ...m23, ...p3],
]
}
/**
* The dashes between two beads, as the adapter lays them: `dash` on and `gap`
* off along the line in the model's own units, each dash projected on its
* own. At most two hundred, so a radius of nothing cannot ask for infinitely
* many.
*/
function dashesBetween(
camera: Camera,
box: { width: number; height: number },
structure: Structure,
a: number,
b: number,
dash: number,
gap: number,
): Array<[number, number, number, number]> {
const from: [number, number, number] = [structure.x[a], structure.y[a], structure.z[a]]
const to: [number, number, number] = [structure.x[b], structure.y[b], structure.z[b]]
const length = Math.hypot(to[0] - from[0], to[1] - from[1], to[2] - from[2])
if (!(length > 0)) return []
const step = Math.max(dash + gap, length / 200)
const on = dash * (step / Math.max(dash + gap, 1e-12))
const out: Array<[number, number, number, number]> = []
const along = (d: number): [number, number, number] => [
from[0] + ((to[0] - from[0]) * d) / length,
from[1] + ((to[1] - from[1]) * d) / length,
from[2] + ((to[2] - from[2]) * d) / length,
]
for (let at = 0; at < length; at += step) {
const p = along(at)
const q = along(Math.min(length, at + on))
const pp = project(camera, box, p[0], p[1], p[2])
const qq = project(camera, box, q[0], q[1], q[2])
if (pp === null || qq === null) continue
out.push([pp.px, pp.py, qq.px, qq.py])
}
return out
}
/**
* The centre of rotation as the adapter builds it (`structure/three.ts`): a
* ball of ink at the camera's target and an arm per axis of the model's
* planted frame — a shaft and a head on the positive side, a thin stub on the
* negative — in the axis colours. Flat, as the adapter's are, and sorted far to
* near among themselves, as three sorts its transparent parts.
*
* Each part is the outline a cylinder or a cone casts under the projection:
* the convex hull of its circles' projected points and its tip. Exact for the
* orthographic projection every model is drawn in, and right at every angle —
* an arm pointing at the reader is the small disc the screen shows, not a line
* of no length.
*/
function drawCentre(
ctx: CanvasRenderingContext2D,
box: { width: number; height: number },
view: StructureView,
palette: PainterPalette,
): void {
const { camera, style } = view
const size = camera.distance * CENTRE.size
const [tx, ty, tz] = camera.target
const centre = project(camera, box, tx, ty, tz)
if (centre === null) return
const axes = frameAxes(style.axesFrame)
const point = (dir: readonly number[], along: number): [number, number, number] => [
tx + dir[0] * along * size,
ty + dir[1] * along * size,
tz + dir[2] * along * size,
]
const parts: Array<{ depth: number; draw: () => void }> = [
{
depth: centre.depth,
draw: () => {
ctx.globalAlpha = CENTRE.ballOpacity
ctx.fillStyle = palette.ink
ctx.beginPath()
ctx.arc(centre.px, centre.py, Math.max(1, CENTRE.ball * size * centre.pixelsPerUnit), 0, Math.PI * 2)
ctx.fill()
},
},
]
;[axes.x, axes.y, axes.z].forEach((dir, index) => {
const colour = CENTRE.colours[index]
for (const part of [CENTRE.shaft, CENTRE.head, CENTRE.stub]) {
const base = point(dir, part.from)
const tip = point(dir, part.to)
const middle = point(dir, (part.from + part.to) / 2)
const ring = (at: [number, number, number]): Array<[number, number]> =>
circlePoints(at, dir, part.radius * size).flatMap((p) => {
const projected = project(camera, box, p[0], p[1], p[2])
return projected === null ? [] : [[projected.px, projected.py] as [number, number]]
})
const cone = part === CENTRE.head
const outline = convexHull([
...ring(base),
...(cone
? (() => {
const t = project(camera, box, tip[0], tip[1], tip[2])
return t === null ? [] : [[t.px, t.py] as [number, number]]
})()
: ring(tip)),
])
if (outline.length < 3) continue
const at = project(camera, box, middle[0], middle[1], middle[2])
parts.push({
depth: at === null ? centre.depth : at.depth,
draw: () => {
ctx.globalAlpha = CENTRE.armOpacity
ctx.fillStyle = colour
ctx.beginPath()
ctx.moveTo(outline[0][0], outline[0][1])
for (const [x, y] of outline.slice(1)) ctx.lineTo(x, y)
ctx.closePath()
ctx.fill()
},
})
}
})
parts.sort((m, o) => o.depth - m.depth)
for (const part of parts) part.draw()
ctx.globalAlpha = 1
}
/** Sixteen points round a circle in 3D: centre, the axis it is square to, radius. */
function circlePoints(
centre: [number, number, number],
axis: readonly number[],
radius: number,
): Array<[number, number, number]> {
const helper = Math.abs(axis[0]) < 0.9 ? [1, 0, 0] : [0, 1, 0]
const cross = (p: readonly number[], q: readonly number[]): number[] => [
p[1] * q[2] - p[2] * q[1],
p[2] * q[0] - p[0] * q[2],
p[0] * q[1] - p[1] * q[0],
]
const u0 = cross(axis, helper)
const length = Math.hypot(u0[0], u0[1], u0[2]) || 1
const u = u0.map((v) => v / length)
const v = cross(axis, u)
const out: Array<[number, number, number]> = []
for (let k = 0; k < 16; k++) {
const angle = (k / 16) * Math.PI * 2
const c = Math.cos(angle) * radius
const s = Math.sin(angle) * radius
out.push([centre[0] + u[0] * c + v[0] * s, centre[1] + u[1] * c + v[1] * s, centre[2] + u[2] * c + v[2] * s])
}
return out
}
/** The convex hull of points on the page, in order round it (Andrew's monotone chain). */
function convexHull(points: Array<[number, number]>): Array<[number, number]> {
const sorted = [...points].sort((p, q) => p[0] - q[0] || p[1] - q[1])
if (sorted.length < 3) return sorted
const turn = (o: [number, number], a: [number, number], b: [number, number]): number =>
(a[0] - o[0]) * (b[1] - o[1]) - (a[1] - o[1]) * (b[0] - o[0])
const lower: Array<[number, number]> = []
for (const p of sorted) {
while (lower.length >= 2 && turn(lower[lower.length - 2], lower[lower.length - 1], p) <= 0) lower.pop()
lower.push(p)
}
const upper: Array<[number, number]> = []
for (let k = sorted.length - 1; k >= 0; k--) {
const p = sorted[k]
while (upper.length >= 2 && turn(upper[upper.length - 2], upper[upper.length - 1], p) <= 0) upper.pop()
upper.push(p)
}
return [...lower.slice(0, -1), ...upper.slice(0, -1)]
}
/** Whether a bead of the model is drawn at all, before the slab is asked. */
function visible(view: StructureView, i: number): boolean {
const { structure, style } = view
if (structure.present[i] === 0) return false
if (view.haplotype >= 0 && structure.model.hap[i] !== view.haplotype) return false
if (view.lit !== null && view.lit[i] === 0 && style.others === 'hide') return false
return true
}
/** Every bead of a model on the page, and which of them are drawn. */
function placeAll(
structure: Structure,
camera: Camera,
box: { width: number; height: number },
inSlab: (x: number, y: number, z: number) => boolean,
keep: (i: number) => boolean,
): Placed {
const n = structure.set.length
const placed: Placed = {
px: new Float64Array(n),
py: new Float64Array(n),
depth: new Float64Array(n),
size: new Float64Array(n),
drawn: new Uint8Array(n),
}
for (let i = 0; i < n; i++) {
if (!keep(i)) continue
const x = structure.x[i]
const y = structure.y[i]
const z = structure.z[i]
if (!inSlab(x, y, z)) continue
const at = project(camera, box, x, y, z)
if (at === null) continue
placed.px[i] = at.px
placed.py[i] = at.py
placed.depth[i] = at.depth
placed.size[i] = at.pixelsPerUnit
placed.drawn[i] = 1
}
return placed
}
/**
* Half the slab's thickness, in the scene's units — the adapter's own: the
* model's reach from its centre, times the slab. Measured on every bead the
* file placed, so it is a fact about the model and not about the window.
*/
function slabHalf(structure: Structure, style: StructureStyle): number {
const all = centroidOf(structure, counting(structure.set.length))
const reach = all === null ? 1 : Math.max(1e-3, all.radius)
return Math.max(1e-3, reach * style.slab)
}
/** Whether a point lies between the slab's two planes; everything does at a slab of one. */
function slabTest(
camera: Camera,
style: StructureStyle,
half: number,
): (x: number, y: number, z: number) => boolean {
if (!(style.slab < 1)) return () => true
const { forward } = basis(camera)
const [tx, ty, tz] = camera.target
return (x, y, z) => {
const along = (x - tx) * forward[0] + (y - ty) * forward[1] + (z - tz) * forward[2]
return along >= -half && along <= half
}
}
/**
* How far into the fog a depth is, from 0 to 1 — the adapter's fog, as
* arithmetic.
*
* Linear fog in three.js is a smoothstep between where it starts and where it
* reaches the page, and the adapter starts it at the centre of rotation — the
* plane the slab is centred on — and has it reach the page `half / fog`
* further back, so what it says is how close a bead is to being cut away. Off
* is nothing.
*/
export function fogAt(camera: Camera, style: StructureStyle, half: number): (depth: number) => number {
if (!style.fogOn || !(style.fog > 0)) return () => 0
const near = camera.distance
const far = near + half / style.fog
return (depth) => {
const t = Math.max(0, Math.min(1, (depth - near) / Math.max(1e-12, far - near)))
return t * t * (3 - 2 * t)
}
}
/** `0, 1, … n − 1`, for a helper that wants an iterable of every bead. */
function* counting(n: number): Generator<number, void, void> {
for (let i = 0; i < n; i++) yield i
}
/** A colour mixed towards another by `t`. */
function unit(v: [number, number, number]): [number, number, number] {
const length = Math.hypot(v[0], v[1], v[2]) || 1
return [v[0] / length, v[1] / length, v[2] / length]
}
/** A colour under the screen's lights, on a surface facing `normal` (camera frame, unit). */
export function shade(colour: Rgb, normal: [number, number, number]): Rgb {
const dot = (l: readonly number[]): number => Math.max(0, normal[0] * l[0] + normal[1] * l[1] + normal[2] * l[2])
const light = AMBIENT + KEY_WEIGHT * dot(KEY) + FILL_WEIGHT * dot(FILL)
const lit: Rgb = [
Math.min(1, colour[0] * light),
Math.min(1, colour[1] * light),
Math.min(1, colour[2] * light),
]
return mix(lit, [1, 1, 1], SPECULAR * dot(HIGHLIGHT) ** SHININESS)
}
/**
* The colour a lit sphere has `t` of the way from its highlight (`0`) out to
* the point of its silhouette furthest from the light (`1`).
*
* The family of circles a radial shading sweeps — from a point at the
* highlight to the whole disc, centre and radius growing together — has each
* circle's far side `t` of the way along that line, and the far side is most
* of what each band shows; so that is the normal the band is lit by. The same
* profile across a tube's width is the cylinder's, near enough at the widths a
* figure reads it at.
*/
function sphereAt(colour: Rgb, t: number): Rgb {
const [hx, hy] = [HIGHLIGHT[0], HIGHLIGHT[1]]
const away = Math.hypot(hx, hy) || 1
const x = (1 - t) * hx - (t * hx) / away
const y = (1 - t) * hy - (t * hy) / away
const z = Math.sqrt(Math.max(0, 1 - x * x - y * y))
return shade(colour, [x, y, z])
}
/**
* A bead as a lit sphere: a radial gradient from a point at its highlight to
* the whole disc, its stops fogged as the bead is. One flat colour where the
* bead is too small to shade, and on a context without gradients.
*/
function sphereFill(
ctx: CanvasRenderingContext2D,
x: number,
y: number,
radius: number,
colour: Rgb,
fogged: (rgb: Rgb) => string,
): string | CanvasGradient {
if (radius < TUBE_SHADED_MIN / 2 || typeof ctx.createRadialGradient !== 'function') {
return fogged(sphereAt(colour, 0.5))
}
// Canvas y runs down the page; the camera's runs up it.
const gradient = ctx.createRadialGradient(
x + HIGHLIGHT[0] * radius,
y - HIGHLIGHT[1] * radius,
0,
x,
y,
radius,
)
for (let k = 0; k <= SPHERE_STOPS; k++) {
const t = k / SPHERE_STOPS
gradient.addColorStop(t, fogged(sphereAt(colour, t)))
}
return gradient
}
/**
* A lit line `width` across, as bands to lay one over the next along the
* same path: from the full width in the shadow of its rim to a narrow
* highlight, each a share `outer` of the width, nudged towards the light by
* as much as it is narrower ({@link nudgeOf}).
*
* The nudge is one vector for a whole path, and a vector moves a line only
* across itself, so a tube running towards the light is lit along its middle
* and one running across it on its lit side — which is what a cylinder does.
* One flat band, the surface's own colour, for a ghosted line (bands at an
* alpha would add up) or one too thin to shade.
*/
function bandsOf(width: number, alpha: number): Array<{ outer: number; shade: (colour: Rgb) => Rgb }> {
if (alpha < 1 || width < TUBE_SHADED_MIN) return [{ outer: 1, shade: (colour) => colour }]
const count = Math.min(BANDS_MAX, Math.max(BANDS_MIN, Math.ceil(width / 2 / BAND_WIDTH)))
const bands: Array<{ outer: number; shade: (colour: Rgb) => Rgb }> = []
for (let k = 0; k < count; k++) {
const middle = 1 - (k + 0.5) / count
bands.push({ outer: 1 - k / count, shade: (colour) => sphereAt(colour, middle) })
}
return bands
}
/** How far a band a share `outer` of a line `width` across is moved towards the light, in canvas pixels. */
function nudgeOf(width: number, outer: number): [number, number] {
const nudge = ((1 - outer) * width) / 2
// Canvas y runs down the page; the camera's runs up it.
return [HIGHLIGHT[0] * nudge, -HIGHLIGHT[1] * nudge]
}
/** A point on a tube's centreline: where, which way it runs, and how wide the tube is there. */
interface Station {
x: number
y: number
/** The unit tangent. */
tx: number
ty: number
width: number
}
/**
* A stretch's centreline as stations, from `overlap` before its first
* midpoint to `overlap` past its last, the width running linearly from each
* midpoint's to the bead's along each half-span.
*/
function centreline(
into: number[] | null,
out: number[] | null,
back: [number, number] | null,
on: [number, number] | null,
centre: [number, number],
before: number,
width: number,
after: number,
overlap: number,
): Station[] {
const stations: Station[] = []
const along = (half: number[], from: number, to: number, skipFirst: boolean, fallback: [number, number]): void => {
const reach =
Math.hypot(half[2] - half[0], half[3] - half[1]) +
Math.hypot(half[4] - half[2], half[5] - half[3]) +
Math.hypot(half[6] - half[4], half[7] - half[5])
const steps = Math.min(16, Math.max(2, Math.ceil(reach / OUTLINE_STEP)))
let tangent = fallback
for (let i = skipFirst ? 1 : 0; i <= steps; i++) {
const t = i / steps
const u = 1 - t
const x = u * u * u * half[0] + 3 * u * u * t * half[2] + 3 * u * t * t * half[4] + t * t * t * half[6]
const y = u * u * u * half[1] + 3 * u * u * t * half[3] + 3 * u * t * t * half[5] + t * t * t * half[7]
const dx = 3 * u * u * (half[2] - half[0]) + 6 * u * t * (half[4] - half[2]) + 3 * t * t * (half[6] - half[4])
const dy = 3 * u * u * (half[3] - half[1]) + 6 * u * t * (half[5] - half[3]) + 3 * t * t * (half[7] - half[5])
const length = Math.hypot(dx, dy)
if (length > 1e-9) tangent = [dx / length, dy / length]
stations.push({ x, y, tx: tangent[0], ty: tangent[1], width: from + (to - from) * t })
}
}
if (into !== null && back !== null) {
stations.push({ x: into[0] - back[0] * overlap, y: into[1] - back[1] * overlap, tx: back[0], ty: back[1], width: before })
along(into, before, width, false, back)
}
if (out !== null && on !== null) {
const start = into === null ? towards(out, 0) : [stations[stations.length - 1].tx, stations[stations.length - 1].ty]
along(out, width, after, into !== null, start as [number, number])
stations.push({ x: out[6] + on[0] * overlap, y: out[7] + on[1] * overlap, tx: on[0], ty: on[1], width: after })
}
if (stations.length === 0) stations.push({ x: centre[0], y: centre[1], tx: 1, ty: 0, width })
return stations
}
/**
* One side of a band of a tube, as a closed subpath: its edge on that side
* (`side` `1` or `-1`) out and back along the band `inner` of the width in,
* or along the other side's edge for the band in the middle (`inner` null).
*
* A band is a share of the tube's width wherever it is, so it narrows and
* widens with the tube and meets its neighbour's at the midpoint exactly.
*/
function ribbon(
ctx: CanvasRenderingContext2D,
line: Station[],
outer: number,
inner: number | null,
side: 1 | -1,
): void {
if (inner === null && side === -1) return
const edge = (station: Station, share: number, which: 1 | -1): [number, number] => {
const [dx, dy] = nudgeOf(station.width, share)
const half = (station.width * share) / 2
return [station.x + dx - station.ty * half * which, station.y + dy + station.tx * half * which]
}
line.forEach((station, i) => {
const [x, y] = edge(station, outer, side)
if (i === 0) ctx.moveTo(x, y)
else ctx.lineTo(x, y)
})
for (let i = line.length - 1; i >= 0; i--) {
const [x, y] = inner === null ? edge(line[i], outer, -1) : edge(line[i], inner, side)
ctx.lineTo(x, y)
}
ctx.closePath()
}
function mix(colour: Rgb, towards: Rgb, t: number): Rgb {
if (!(t > 0)) return colour
return [
colour[0] + (towards[0] - colour[0]) * t,
colour[1] + (towards[1] - colour[1]) * t,
colour[2] + (towards[2] - colour[2]) * t,
]
}
/** `0..1` channels as the `rgb()` the page writes, rounded to a byte. */
function css(rgb: Rgb): string {
const byte = (v: number): number => Math.round(Math.max(0, Math.min(1, v)) * 255)
return `rgb(${byte(rgb[0])}, ${byte(rgb[1])}, ${byte(rgb[2])})`
}
/**
* The weight of the rule round a model's cell in an exported figure, in CSS
* pixels: the map's plot border's (`render/heatmap.ts`), so the two cells of a
* deck are framed alike.
*/
export const CELL_FRAME_WIDTH = 0.75
/**
* The cell's edge, as a thin rule round an exported model (§25.7).
*
* A model zoomed past its cell is cut by the cell's edge, and on screen the
* cell's own border says where the cut is. Exported without one it floats on
* the page with a straight side sliced off it for no visible reason — so every
* export draws the edge: the deck's figure, the card's PNG and PDF and the
* clipboard. Inset by half its width, so the whole of the line is on the page
* rather than half of it cut by the page's own edge.
*/
export function drawCellFrame(
ctx: CanvasRenderingContext2D,
box: { width: number; height: number },
colour: string,
width: number,
): void {
ctx.save()
ctx.setLineDash([])
ctx.strokeStyle = colour
ctx.lineWidth = width
ctx.strokeRect(width / 2, width / 2, box.width - width, box.height - width)
ctx.restore()
}
/** A neutral palette for a figure on paper. */
export const PAPER_PALETTE: PainterPalette = {
background: '#ffffff',
ink: '#222222',
halo: '#ffffff',
}
/** What the painter draws a bead it knows nothing about in. */
export const PAINTER_UNSET = UNSET_COLOUR
|