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// abstract base + registry mechanics.
import {Animation, AllAnimations, IAnimationStep, registerAnimation} from "../Animations";
import {GeomElement} from "../GeomElement";
import {Slate} from "../../Slate";
import {CircleElement} from "./CircleElement";
import {PointElement} from "../point/PointElement";
import {LineElement} from "../line/LineElement";
import {PolygonElement} from "../polygon/PolygonElement";
// Default sweep rate in radians/ms. Calibrated for unhurried teaching:
// a full circle (2π) draws in ≈ 2 seconds at 0.003 rad/ms. Authors who
// want a faster compass raise the rate via
// slate.animationConfig.rates["Circle.compass"].
const DEFAULT_ARC_RATE_RAD_PER_MS = 0.003;
// A.Circle.compass — anchor at centre, pick up the pencil at the
// radius-defining point B, sweep 2π back to the start. Args:
// { startAngle?: number } — default is computed from the angle from
// centre to B so the trace begins where a real compass would.
//
// Strict two-step sequence (mirrors A.Polygon.outlineAndFill):
// 1. Edge sweep: drawProgress 0 → 1 over 2π / rate.
// 2. Face fade-in: faceAlpha 0 → 1 over ~half the sweep duration.
// The edge stays fully drawn through step 2 because drawProgress
// finalises to 1 before the fade-in starts, and faceAlpha is the
// independent driver for drawFace's globalAlpha.
const DEFAULT_CIRCLE_FILL_MS = 600;
export class CircleCompassAnimation extends Animation {
public animationMethod = AllAnimations.CIRCLE_COMPASS;
public name = "Circle.compass";
public elementType = CircleElement;
public defaultRate = DEFAULT_ARC_RATE_RAD_PER_MS;
public defaultDurationMs = DEFAULT_CIRCLE_FILL_MS;
public build(target: GeomElement, slate: Slate, args: any): IAnimationStep[] {
const circle = target as CircleElement;
const explicitStart = (args && typeof args.startAngle === "number")
? args.startAngle
: Math.atan2(circle.B.y - circle.Center.y, circle.B.x - circle.Center.x);
const sweepMs = (2 * Math.PI) / this.defaultRate;
const fullRestore = () => {
circle.faceAlpha = 1;
circle.drawProgress = 1;
circle.drawStartAngle = 0;
circle.visible = true;
};
// Step 1 — edge sweep with the face hidden.
const sweep: IAnimationStep = {
durationMs: sweepMs,
setup: () => {
circle.drawStartAngle = explicitStart;
circle.faceAlpha = 0;
circle.drawProgress = 0;
},
tick: (progress) => { circle.drawProgress = progress; },
finalise: () => { circle.drawProgress = 1; },
};
// A face-less circle has nothing to fade — scheduling the
// fill step anyway would be pure dead time in the middle of
// a cascade (#81). Run the sweep alone, with its finalise
// doing the full restore.
if (circle.faceColor == null) {
sweep.finalise = fullRestore;
return [sweep];
}
// Fill ~twice as fast as the sweep, capped by the class-level
// default so a tiny circle doesn't yield a blink-of-an-eye fade.
const fillMs = Math.min(sweepMs / 2, this.defaultDurationMs);
return [
sweep,
// Step 2 — face fade-in over the now-complete arc.
{
durationMs: fillMs,
tick: (progress) => { circle.faceAlpha = progress; },
finalise: fullRestore,
},
];
}
}
registerAnimation(new CircleCompassAnimation());
// A.Circle.compassTransfer — Euclid I.2 (copy a length to a point) as one
// animation. The target is the declared RADIUS circle the deck keeps: a
// `circle;radius;P,C,D` (centre P, radius the length |CD| to copy). The
// macro reads P + the source CD straight off the target, draws the rigorous
// I.2 walk that justifies that radius — join, the two I.1 circles + the
// equilateral triangle, the two produced sides, and the two lay-off circles —
// nine steps, all transitory gold EPHEMERALS
// (created in step-1 setup, cleared in the last finalise), then reveals the
// circle. The result is a circle, so its scaffolding side is a free visual
// choice (args.side, default +1). A deck calls one entry instead of declaring
// and sequencing the ~8-element rig.
//
// Geometry (P = centre, C = near source end, D = far, r = |CD|):
// T = equilateral apex of P,C M = C + r·unit(C−T) (CM = r, on circle(C,r))
// N = T + (|TC|+r)·unit(P−T) (PN = r, on circle(T,|TM|)) → the kept radius
const CIRCLE_TRANSFER_SWEEP_RATE = 0.0055; // rad/ms — brisk for a long walk
const CIRCLE_TRANSFER_TRACE_RATE = 0.3; // px/ms for the straightedge traces
function equilateralApex(A: PointElement, B: PointElement, side: number): { x: number, y: number } {
const mx = (A.x + B.x) / 2, my = (A.y + B.y) / 2;
const dx = B.x - A.x, dy = B.y - A.y;
const len = Math.hypot(dx, dy) || 1;
const h = len * Math.sqrt(3) / 2;
// perpendicular unit (rotate the base 90°), times the chosen side
return { x: mx + side * h * (-dy / len), y: my + side * h * (dx / len) };
}
export class CircleCompassTransferAnimation extends Animation {
public animationMethod = AllAnimations.CIRCLE_COMPASS_TRANSFER;
public name = "Circle.compassTransfer";
public elementType = CircleElement;
public defaultRate = CIRCLE_TRANSFER_SWEEP_RATE;
public defaultDurationMs = DEFAULT_CIRCLE_FILL_MS;
public build(target: GeomElement, slate: Slate, args: any): IAnimationStep[] {
const circ = target as CircleElement;
const P = circ.Center;
const s0 = circ.A, s1 = circ.B;
const instant = (): IAnimationStep[] => [{
durationMs: 0, tick: () => {},
finalise: () => { circ.faceAlpha = 1; circ.drawProgress = 1; circ.visible = true; },
}];
// Need a radius defined by two distinct source points (the length to
// copy), distinct from the centre — i.e. circle;radius;P,C,D.
if (s0 == null || s1 == null || s0 === P || s1 === P || s0.distance(s1) < 1e-6) {
slate.reportDiagnostic({
code: "bad-animation-args",
key: "Circle.compassTransfer|" + String(circ.name),
message: "Circle.compassTransfer: needs a radius defined by two "
+ "points distinct from the centre (circle;radius;centre,p1,p2) — skipping",
detail: { animation: "Circle.compassTransfer", elem: String(circ.name) },
});
return instant();
}
const plane = (P as any).AP || circ.AP;
const r = s0.distance(s1);
// Near source end joins the centre; far end is the length's reach.
const C = (P.distance(s0) <= P.distance(s1)) ? s0 : s1;
const D = (C === s0) ? s1 : s0;
const side = (args && (args.side === 1 || args.side === -1)) ? args.side : 1;
const t = equilateralApex(P, C, side);
const T = new PointElement(); T.x = t.x; T.y = t.y; (T as any).AP = plane;
const TC = Math.hypot(C.x - t.x, C.y - t.y) || 1;
// M = C + r·unit(C − T); N = T + (TC + r)·unit(P − T)
const u1x = (C.x - t.x) / TC, u1y = (C.y - t.y) / TC;
const M = new PointElement(); M.x = C.x + r * u1x; M.y = C.y + r * u1y; (M as any).AP = plane;
const TP = Math.hypot(P.x - t.x, P.y - t.y) || 1;
const u2x = (P.x - t.x) / TP, u2y = (P.y - t.y) / TP;
const N = new PointElement(); N.x = t.x + (TC + r) * u2x; N.y = t.y + (TC + r) * u2y; (N as any).AP = plane;
// Transitory gold scaffolding (bare ephemerals).
const join = new LineElement({ A: P, B: C });
const tri = new PolygonElement(); tri.V = [P, C, T];
const prodM = new LineElement({ A: C, B: M }); // produced side, C → M
const prodN = new LineElement({ A: P, B: N }); // produced side, P → N (carries the result)
const circC = new CircleElement({ C: C, B: D, AP: plane }); // circle(C, r): thru D and M
const circT = new CircleElement({ C: T, B: M, AP: plane }); // circle(T, |TM|): thru M and N
const circEp = new CircleElement({ C: P, B: C, AP: plane }); // I.1 circle: centre P thru C
const circEc = new CircleElement({ C: C, B: P, AP: plane }); // I.1 circle: centre C thru P
const transitory: GeomElement[] = [join, tri, prodM, prodN];
// The four construction circles, in walk order (2 equilateral, 2 lay-off).
const circles: CircleElement[] = [circEp, circEc, circC, circT];
for (const e of (transitory as GeomElement[]).concat(circles)) {
(e as any).edgeColor = null; (e as any).faceColor = null;
(e as any).nameColor = null; (e as any).vertexColor = null;
e.emphasized = true; // paints in the gold highlight stroke
}
// keepCircles: name the four circles so they persist as real, named
// elements (rather than being wiped on slide advance) — a later slide
// can re-show / count them. Order matches I.23's [t1Ka, t1Kc, t1Kc2, t1KT].
const keepNames: string[] | null =
(args && Array.isArray(args.keepCircles)) ? args.keepCircles : null;
if (keepNames) circles.forEach((c, i) => { if (keepNames[i]) c.name = String(keepNames[i]); });
const isKept = (c: CircleElement) => keepNames != null && c.name != null;
const sweepMs = (2 * Math.PI) / this.defaultRate;
const traceMs = (a: PointElement, b: PointElement) =>
Math.max(120, a.distance(b) / CIRCLE_TRANSFER_TRACE_RATE);
const lineStep = (ln: LineElement, ms: number): IAnimationStep => ({
durationMs: ms,
setup: () => { ln.drawProgress = 0; },
tick: (p) => { ln.drawProgress = p; },
finalise: () => { ln.drawProgress = 1; },
});
const sweepStep = (c: CircleElement): IAnimationStep => ({
durationMs: sweepMs,
setup: () => { c.drawStartAngle = Math.atan2(c.B.y - c.Center.y, c.B.x - c.Center.x); c.drawProgress = 0; },
tick: (p) => { c.drawProgress = p; },
finalise: () => { c.drawProgress = 1; },
});
// Clear the transitory scaffolding; kept circles persist (the slideshow's
// visible-set hides them on advance and can re-show them for a count).
const clearScaffold = () => {
for (const e of transitory) slate.removeEphemeral(e);
for (const c of circles) if (!isKept(c)) slate.removeEphemeral(c);
};
// Step 1 — join P→C; also registers all scaffolding and hides the
// result circle until the reveal.
const step1 = lineStep(join, traceMs(P, C));
step1.setup = () => {
circ.drawProgress = 0; circ.faceAlpha = 0; // result stays dark until reveal
for (const e of transitory) { slate.addEphemeral(e); (e as any).drawProgress = 0; }
for (const c of circles) {
c.drawProgress = 0;
if (isKept(c)) {
slate.addElement(c); // persist as a real, named element
slate.setInitiallyHidden(c.name!); // keep it out of the post-presentation figure
c.visible = true; // but show it now, through the walk
} else {
slate.addEphemeral(c);
}
}
join.drawProgress = 0;
};
const steps: IAnimationStep[] = [
step1,
// Steps 2,3 — the two I.1 compass circles that fix the equilateral apex.
sweepStep(circEp),
sweepStep(circEc),
// Step 4 — the equilateral triangle PCT traces.
{ durationMs: traceMs(P, C) + traceMs(C, T),
setup: () => { tri.drawProgress = 0; },
tick: (p) => { tri.drawProgress = p; },
finalise: () => { tri.drawProgress = 1; } },
// Steps 5,6 — produce the two sides.
lineStep(prodM, traceMs(C, M)),
lineStep(prodN, traceMs(P, N)),
// Steps 7,8 — the two lay-off compass circles.
sweepStep(circC),
sweepStep(circT),
];
// Step 7 — reveal the result radius circle, clearing the scaffold as it lands.
const reveal: IAnimationStep = {
durationMs: sweepMs,
setup: () => {
circ.drawStartAngle = Math.atan2(circ.B.y - P.y, circ.B.x - P.x);
circ.drawProgress = 0; circ.faceAlpha = 0; circ.visible = true;
},
tick: (p) => { circ.drawProgress = p; },
finalise: () => { circ.drawProgress = 1; circ.faceAlpha = 1; circ.visible = true; clearScaffold(); },
};
steps.push(reveal);
return steps;
}
}
registerAnimation(new CircleCompassTransferAnimation());
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