Maxim Dolgolyov
fd29acbbdd
Classroom performance: - WebSocket server (ws-server.js) for low-latency cursor & stroke preview Replaces HTTP POST per event → eliminates per-message auth overhead Session member cache (30s TTL) avoids SQLite query per WS message Fallback to HTTP POST when WS not connected - Cursor throttle reduced 100ms → 33ms (~30fps) - Stroke preview throttle reduced 50ms → 20ms - whiteboard.js: render() is now rAF-gated (_doRender/_rafPending) Multiple render() calls within one frame collapse into one repaint document.hidden check — zero CPU when tab is in background visibilitychange listener restores canvas on tab focus Guest board: - guestClassroom.js route: public token-based read-only access - guest-board.html: name entry + read-only whiteboard + SSE - SSE: addGuestClient/removeGuestClient/emitToGuests Screen share picker: - Discord-style modal with tab switching (screen/window/tab) - Live video preview before confirming share - useExistingScreenStream() in ClassroomRTC Fullscreen exit overlay: - #cr-fs-exit-overlay button inside cr-board-wrap - Visible only via CSS :fullscreen selector (touchpad users) File sharing from library: - Teacher picks file from library, sends as styled card in chat - crDownloadLibraryFile() fetches with Bearer auth Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
435 lines
14 KiB
JavaScript
435 lines
14 KiB
JavaScript
'use strict';
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/* ══════════════════════════════════════════════════════════════
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QuadraticSim — interactive quadratic equation explorer
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y = ax² + bx + c · discriminant, roots, vertex
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══════════════════════════════════════════════════════════════ */
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class QuadraticSim {
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constructor(canvas) {
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this.canvas = canvas;
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this.ctx = canvas.getContext('2d');
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this.W = 0; this.H = 0;
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/* coefficients */
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this.a = 1;
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this.b = 0;
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this.c = -1;
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/* view */
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this.ox = 0;
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this.oy = 0;
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this.scl = 40; // px per unit
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/* interaction */
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this._drag = null;
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this.hx = null; // hovered math x
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/* callback */
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this.onUpdate = null;
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this._bind();
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new ResizeObserver(() => { this.fit(); this.draw(); }).observe(canvas.parentElement);
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}
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/* ── public API ───────────────────────────────────── */
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fit() {
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const dpr = window.devicePixelRatio || 1;
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const w = this.canvas.offsetWidth || 600;
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const h = this.canvas.offsetHeight || 400;
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this.canvas.width = w * dpr;
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this.canvas.height = h * dpr;
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this.ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
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this.W = w; this.H = h;
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}
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getParams() { return { a: this.a, b: this.b, c: this.c }; }
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setParams({ a, b, c } = {}) {
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if (a !== undefined) this.a = +a;
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if (b !== undefined) this.b = +b;
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if (c !== undefined) this.c = +c;
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this.draw();
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this._emit();
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}
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resetView() { this.ox = 0; this.oy = 0; this.scl = 40; this.draw(); }
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zoomIn() { this.scl = Math.min(800, this.scl * 1.3); this.draw(); }
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zoomOut() { this.scl = Math.max(4, this.scl / 1.3); this.draw(); }
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info() {
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const { a, b, c } = this;
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const D = b * b - 4 * a * c;
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let roots = '—';
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let rootCount = 0;
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if (a === 0) {
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roots = b !== 0 ? `x = ${this._fmt(-c / b)}` : '—';
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rootCount = b !== 0 ? 1 : 0;
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} else if (D > 0.0001) {
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const sqD = Math.sqrt(D);
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const x1 = (-b - sqD) / (2 * a);
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const x2 = (-b + sqD) / (2 * a);
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roots = `x₁=${this._fmt(x1)}, x₂=${this._fmt(x2)}`;
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rootCount = 2;
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} else if (Math.abs(D) <= 0.0001) {
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roots = `x = ${this._fmt(-b / (2 * a))}`;
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rootCount = 1;
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}
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const vx = a !== 0 ? -b / (2 * a) : 0;
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const vy = a !== 0 ? c - b * b / (4 * a) : 0;
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return {
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D: this._fmt(D),
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rootCount,
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roots,
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vertex: a !== 0 ? `(${this._fmt(vx)}; ${this._fmt(vy)})` : '—',
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equation: `y = ${a !== 1 ? (a === -1 ? '−' : this._fmt(a)) : ''}x² ${b >= 0 ? '+' : '−'} ${this._fmt(Math.abs(b))}x ${c >= 0 ? '+' : '−'} ${this._fmt(Math.abs(c))}`,
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};
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}
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/* ── internals ────────────────────────────────────── */
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_fmt(n) {
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if (Number.isInteger(n)) return String(n);
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return Math.abs(n) < 0.005 ? '0' : n.toFixed(2).replace(/\.?0+$/, '');
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}
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_f(x) {
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return this.a * x * x + this.b * x + this.c;
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}
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_emit() {
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if (this.onUpdate) this.onUpdate(this.info());
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}
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/* ── coordinate transforms ─────────────────────────── */
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_toPx(mx, my) {
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return [
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this.W / 2 + (mx - this.ox) * this.scl,
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this.H / 2 - (my - this.oy) * this.scl,
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];
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}
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_toMath(px, py) {
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return [
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(px - this.W / 2) / this.scl + this.ox,
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-(py - this.H / 2) / this.scl + this.oy,
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];
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}
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/* ── draw ─────────────────────────────────────────── */
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draw() {
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const ctx = this.ctx, W = this.W, H = this.H;
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if (!W || !H) return;
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ctx.fillStyle = '#0D0D1A';
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ctx.fillRect(0, 0, W, H);
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this._drawGrid(ctx, W, H);
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this._drawAxes(ctx, W, H);
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this._drawParabola(ctx, W, H);
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this._drawFeatures(ctx, W, H);
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if (this.hx !== null) this._drawHover(ctx, W, H);
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}
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/* ── grid & axes ──────────────────────────────────── */
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_niceStep() {
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const raw = this.W / this.scl / 8;
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const p = Math.pow(10, Math.floor(Math.log10(raw)));
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for (const m of [1, 2, 5, 10]) if (m * p >= raw) return m * p;
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return p;
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}
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_drawGrid(ctx, W, H) {
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const step = this._niceStep();
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const [x0] = this._toMath(0, 0), [x1] = this._toMath(W, 0);
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const [, y0] = this._toMath(0, H), [, y1] = this._toMath(0, 0);
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const gx = Math.floor(x0 / step) * step;
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const gy = Math.floor(y0 / step) * step;
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ctx.strokeStyle = 'rgba(255,255,255,0.065)';
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ctx.lineWidth = 1;
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for (let x = gx; x <= x1 + step; x += step) {
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const [px] = this._toPx(x, 0);
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ctx.beginPath(); ctx.moveTo(px, 0); ctx.lineTo(px, H); ctx.stroke();
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}
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for (let y = gy; y <= y1 + step; y += step) {
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const [, py] = this._toPx(0, y);
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ctx.beginPath(); ctx.moveTo(0, py); ctx.lineTo(W, py); ctx.stroke();
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}
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// labels
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ctx.font = '11px Manrope, system-ui, sans-serif';
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ctx.fillStyle = 'rgba(255,255,255,0.3)';
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const [axX, axY] = this._toPx(0, 0);
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const lblY = Math.max(4, Math.min(H - 18, axY + 5));
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const lblX = Math.max(28, Math.min(W - 6, axX - 5));
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ctx.textAlign = 'center'; ctx.textBaseline = 'top';
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for (let x = gx; x <= x1; x += step) {
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if (Math.abs(x) < step * 0.01) continue;
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const [px] = this._toPx(x, 0);
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if (px < 18 || px > W - 18) continue;
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ctx.fillText(this._fmtLabel(x, step), px, lblY);
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}
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ctx.textAlign = 'right'; ctx.textBaseline = 'middle';
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for (let y = gy; y <= y1; y += step) {
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if (Math.abs(y) < step * 0.01) continue;
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const [, py] = this._toPx(0, y);
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if (py < 12 || py > H - 12) continue;
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ctx.fillText(this._fmtLabel(y, step), lblX, py);
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}
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}
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_fmtLabel(n, step) {
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if (n === 0) return '0';
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if (step >= 1 && Number.isInteger(n)) return String(n);
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if (step < 0.001) return n.toExponential(1);
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const dec = Math.max(0, -Math.floor(Math.log10(step)));
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return n.toFixed(dec);
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}
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_drawAxes(ctx, W, H) {
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const [ax, ay] = this._toPx(0, 0);
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ctx.strokeStyle = 'rgba(255,255,255,0.4)';
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ctx.lineWidth = 1.5;
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ctx.beginPath(); ctx.moveTo(0, ay); ctx.lineTo(W - 10, ay); ctx.stroke();
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ctx.beginPath(); ctx.moveTo(ax, H); ctx.lineTo(ax, 8); ctx.stroke();
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// arrowheads
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ctx.fillStyle = 'rgba(255,255,255,0.4)';
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this._arrowHead(ctx, W - 8, ay, 0);
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this._arrowHead(ctx, ax, 6, -Math.PI / 2);
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ctx.fillStyle = 'rgba(255,255,255,0.55)';
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ctx.font = 'bold 12px Manrope, sans-serif';
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ctx.textBaseline = 'middle'; ctx.textAlign = 'left';
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ctx.fillText('x', W - 10, ay - 13);
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ctx.textBaseline = 'top'; ctx.textAlign = 'left';
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ctx.fillText('y', ax + 7, 4);
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}
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_arrowHead(ctx, x, y, angle) {
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const s = 5;
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ctx.save(); ctx.translate(x, y); ctx.rotate(angle);
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ctx.beginPath();
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ctx.moveTo(0, 0); ctx.lineTo(-s * 1.6, -s * 0.6); ctx.lineTo(-s * 1.6, s * 0.6);
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ctx.closePath(); ctx.fill();
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ctx.restore();
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}
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/* ── parabola curve ───────────────────────────────── */
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_drawParabola(ctx, W, H) {
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const steps = Math.min(W * 2, 2000);
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const [x0] = this._toMath(0, 0), [x1] = this._toMath(W, 0);
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const dx = (x1 - x0) / steps;
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// glow
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ctx.strokeStyle = 'rgba(155,93,229,0.15)';
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ctx.lineWidth = 8;
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ctx.lineJoin = 'round';
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ctx.beginPath();
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let pen = false;
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for (let i = 0; i <= steps; i++) {
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const mx = x0 + i * dx;
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const my = this._f(mx);
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if (!isFinite(my)) { pen = false; continue; }
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const [px, py] = this._toPx(mx, my);
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if (py < -200 || py > H + 200) { pen = false; continue; }
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pen ? ctx.lineTo(px, py) : ctx.moveTo(px, py);
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pen = true;
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}
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ctx.stroke();
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// main curve
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ctx.strokeStyle = '#9B5DE5';
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ctx.lineWidth = 2.5;
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ctx.beginPath();
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pen = false;
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for (let i = 0; i <= steps; i++) {
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const mx = x0 + i * dx;
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const my = this._f(mx);
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if (!isFinite(my)) { pen = false; continue; }
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const [px, py] = this._toPx(mx, my);
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if (py < -200 || py > H + 200) { pen = false; continue; }
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pen ? ctx.lineTo(px, py) : ctx.moveTo(px, py);
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pen = true;
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}
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ctx.stroke();
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}
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/* ── vertex, roots, axis of symmetry ──────────────── */
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_drawFeatures(ctx, W, H) {
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const { a, b, c } = this;
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if (a === 0) return; // linear — no features
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const vx = -b / (2 * a);
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const vy = this._f(vx);
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const D = b * b - 4 * a * c;
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// axis of symmetry
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const [symPx] = this._toPx(vx, 0);
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ctx.strokeStyle = 'rgba(6,214,224,0.25)';
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ctx.lineWidth = 1;
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ctx.setLineDash([6, 4]);
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ctx.beginPath(); ctx.moveTo(symPx, 0); ctx.lineTo(symPx, H); ctx.stroke();
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ctx.setLineDash([]);
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// vertex point
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const [vpx, vpy] = this._toPx(vx, vy);
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if (vpy > -20 && vpy < H + 20) {
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ctx.fillStyle = '#06D6E0';
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ctx.beginPath(); ctx.arc(vpx, vpy, 6, 0, Math.PI * 2); ctx.fill();
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ctx.strokeStyle = 'rgba(255,255,255,0.8)'; ctx.lineWidth = 1.5; ctx.stroke();
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// label
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ctx.fillStyle = '#06D6E0';
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ctx.font = 'bold 12px Manrope, sans-serif';
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ctx.textAlign = 'center'; ctx.textBaseline = 'bottom';
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ctx.fillText(`(${this._fmt(vx)}; ${this._fmt(vy)})`, vpx, vpy - 12);
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}
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// roots
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if (D >= -0.0001) {
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ctx.fillStyle = '#EF476F';
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const roots = [];
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if (D > 0.0001) {
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const sqD = Math.sqrt(D);
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roots.push((-b - sqD) / (2 * a));
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roots.push((-b + sqD) / (2 * a));
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} else {
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roots.push(-b / (2 * a));
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}
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for (const rx of roots) {
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const [rpx, rpy] = this._toPx(rx, 0);
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if (rpx < -20 || rpx > W + 20) continue;
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// root dot
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ctx.fillStyle = '#EF476F';
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ctx.beginPath(); ctx.arc(rpx, rpy, 5.5, 0, Math.PI * 2); ctx.fill();
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ctx.strokeStyle = 'rgba(255,255,255,0.8)'; ctx.lineWidth = 1.5; ctx.stroke();
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// label
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ctx.fillStyle = '#EF476F';
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ctx.font = '11px Manrope, sans-serif';
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ctx.textAlign = 'center'; ctx.textBaseline = 'top';
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ctx.fillText(this._fmt(rx), rpx, rpy + 10);
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}
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}
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// discriminant badge
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const badgeColor = D > 0.0001 ? '#7BF5A4' : (D < -0.0001 ? '#EF476F' : '#FFD166');
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const badgeText = D > 0.0001 ? `D = ${this._fmt(D)} > 0 (2 корня)` :
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D < -0.0001 ? `D = ${this._fmt(D)} < 0 (нет корней)` :
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`D = 0 (1 корень)`;
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ctx.font = 'bold 12px Manrope, sans-serif';
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const tw = ctx.measureText(badgeText).width;
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const bx = W - tw - 28, by = 16;
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ctx.fillStyle = 'rgba(22,22,38,0.85)';
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ctx.beginPath(); ctx.roundRect(bx, by, tw + 20, 28, 8); ctx.fill();
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ctx.strokeStyle = badgeColor; ctx.lineWidth = 1;
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ctx.beginPath(); ctx.roundRect(bx, by, tw + 20, 28, 8); ctx.stroke();
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ctx.fillStyle = badgeColor;
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ctx.textAlign = 'left'; ctx.textBaseline = 'middle';
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ctx.fillText(badgeText, bx + 10, by + 14);
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}
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/* ── hover crosshair ──────────────────────────────── */
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_drawHover(ctx, W, H) {
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const [px] = this._toPx(this.hx, 0);
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const my = this._f(this.hx);
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if (!isFinite(my)) return;
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const [, py] = this._toPx(this.hx, my);
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// vertical line
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ctx.strokeStyle = 'rgba(255,255,255,0.15)';
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ctx.lineWidth = 1;
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ctx.setLineDash([5, 5]);
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ctx.beginPath(); ctx.moveTo(px, 0); ctx.lineTo(px, H); ctx.stroke();
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ctx.setLineDash([]);
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if (py < -20 || py > H + 20) return;
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// point
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ctx.fillStyle = '#FFD166';
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ctx.beginPath(); ctx.arc(px, py, 5, 0, Math.PI * 2); ctx.fill();
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ctx.strokeStyle = 'rgba(255,255,255,0.8)'; ctx.lineWidth = 1.5; ctx.stroke();
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// tooltip
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ctx.fillStyle = 'rgba(22,22,38,0.9)';
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const text = `(${this._fmt(this.hx)}, ${this._fmt(my)})`;
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ctx.font = '12px Manrope, sans-serif';
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const tw2 = ctx.measureText(text).width;
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const tx = px + 14, ty = py - 14;
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ctx.beginPath(); ctx.roundRect(tx, ty - 10, tw2 + 16, 22, 6); ctx.fill();
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ctx.fillStyle = '#FFD166';
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ctx.textAlign = 'left'; ctx.textBaseline = 'middle';
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ctx.fillText(text, tx + 8, ty + 1);
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}
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/* ── events ───────────────────────────────────────── */
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_bind() {
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const cv = this.canvas;
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cv.addEventListener('wheel', e => {
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e.preventDefault();
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const [mx, my] = this._toMath(e.offsetX, e.offsetY);
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this.scl = Math.max(4, Math.min(800, this.scl * (e.deltaY < 0 ? 1.15 : 1 / 1.15)));
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const [nx, ny] = this._toMath(e.offsetX, e.offsetY);
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this.ox -= nx - mx; this.oy -= ny - my;
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this.draw();
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}, { passive: false });
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cv.addEventListener('mousedown', e => {
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this._drag = { x: e.clientX, y: e.clientY, ox: this.ox, oy: this.oy };
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cv.style.cursor = 'grabbing';
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});
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window.addEventListener('mousemove', e => {
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if (this._drag) {
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this.ox = this._drag.ox - (e.clientX - this._drag.x) / this.scl;
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this.oy = this._drag.oy + (e.clientY - this._drag.y) / this.scl;
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this.draw();
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} else {
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const r = cv.getBoundingClientRect();
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const lx = e.clientX - r.left, ly = e.clientY - r.top;
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if (lx >= 0 && lx <= r.width && ly >= 0 && ly <= r.height) {
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this.hx = this._toMath(lx, ly)[0];
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this.draw();
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}
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}
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});
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window.addEventListener('mouseup', () => {
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this._drag = null;
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cv.style.cursor = 'crosshair';
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});
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cv.addEventListener('mouseleave', () => {
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this.hx = null; this.draw();
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});
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cv.style.cursor = 'crosshair';
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// touch
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let t0 = null;
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cv.addEventListener('touchstart', e => {
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if (e.touches.length === 1)
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t0 = { x: e.touches[0].clientX, y: e.touches[0].clientY, ox: this.ox, oy: this.oy };
|
||
}, { passive: true });
|
||
cv.addEventListener('touchmove', e => {
|
||
e.preventDefault();
|
||
if (e.touches.length === 1 && t0) {
|
||
this.ox = t0.ox - (e.touches[0].clientX - t0.x) / this.scl;
|
||
this.oy = t0.oy + (e.touches[0].clientY - t0.y) / this.scl;
|
||
this.draw();
|
||
}
|
||
}, { passive: false });
|
||
cv.addEventListener('touchend', () => { t0 = null; });
|
||
}
|
||
}
|