06A Rolling Oscilloscope Whose Rising-Edge Trigger Makes the Trace Hold Still
The first sample crossing the threshold from below is found and one screenful is drawn from there, so a repeating wave starts at the same spot every frame and looks frozen.
Best forInstrument-tuner screens and signal-measurement dashboards
TRIG_LEVELHOLDOFFTRACE_GLOWTIME_DIV
<main class="stage">
<div class="wf is-demo" id="wfRoot">
<canvas class="wf__canvas" data-role="canvas" width="480" height="300" tabindex="0" aria-label="A Rolling Oscilloscope Whose Rising-Edge Trigger Makes the Trace Hold Still"></canvas>
<p class="wf__status" data-role="status" aria-live="polite">Trigger level</p>
<button class="wf__btn" data-role="btn" type="button">Pause</button>
<p class="wf__caption">A Rolling Oscilloscope Whose Rising-Edge Trigger Makes the Trace Hold Still</p>
</div>
</main>@use "../../../../site/static/demo-tokens" as *;
@include stage($stage-ink);
.wf {
position: relative;
width: min(92vw, calc(160vh - 12.8vw));
aspect-ratio: 480 / 300;
margin: 0 auto;
border-radius: $r-card;
overflow: hidden;
box-shadow: $shadow-raised;
background: $subject-ink;
}
.wf__canvas {
display: block;
width: 100%;
height: 100%;
touch-action: pan-x;
}
.wf__canvas:focus-visible {
outline: 2px solid rgba(255, 255, 255, .85);
outline-offset: -6px;
}
.wf__status {
position: absolute;
left: $sp-3;
top: $sp-3;
max-width: 62%;
margin: 0;
padding: $sp-1 $sp-3;
border-radius: $r-pill;
background: rgba(255, 255, 255, .85);
color: $subject-ink;
font-weight: 500;
font-size: 11px;
line-height: 1.4;
pointer-events: none;
}
.wf__btn {
position: absolute;
right: $sp-3;
bottom: $sp-3;
margin: 0;
padding: $sp-1 $sp-3;
border: 0;
border-radius: $r-pill;
background: rgba(255, 255, 255, .85);
color: $subject-ink;
font: inherit;
font-weight: 500;
font-size: 12px;
line-height: 1.4;
cursor: pointer;
}
.wf__btn:focus-visible {
outline: 2px solid #ffffff;
outline-offset: 2px;
}
.wf__caption {
position: absolute;
left: $sp-3;
bottom: $sp-3;
max-width: 68%;
margin: 0;
padding: $sp-1 $sp-3;
border-radius: $r-pill;
background: rgba(255, 255, 255, .85);
color: $subject-ink;
font-weight: 500;
font-size: 12px;
line-height: 1.4;
pointer-events: none;
}
@media (max-width: 340px) {
.wf__caption, .wf__btn { font-size: 10px; padding: $sp-1 $sp-2; }
.wf__status { font-size: 10px; }
}
@media (prefers-reduced-motion: reduce) {
.wf { cursor: default; }
}html, body {
margin: 0;
overflow: hidden;
}
.stage {
box-sizing: border-box;
min-height: 100vh;
display: grid;
place-items: center;
margin: 0;
background: #17141a;
font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
padding: clamp(8px, 4vw, 24px);
}
.wf {
position: relative;
width: min(92vw, 160vh - 12.8vw);
aspect-ratio: 480/300;
margin: 0 auto;
border-radius: 16px;
overflow: hidden;
box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
background: #17141a;
}
.wf__canvas {
display: block;
width: 100%;
height: 100%;
touch-action: pan-x;
}
.wf__canvas:focus-visible {
outline: 2px solid rgba(255, 255, 255, 0.85);
outline-offset: -6px;
}
.wf__status {
position: absolute;
left: 12px;
top: 12px;
max-width: 62%;
margin: 0;
padding: 4px 12px;
border-radius: 999px;
background: rgba(255, 255, 255, 0.85);
color: #17141a;
font-weight: 500;
font-size: 11px;
line-height: 1.4;
pointer-events: none;
}
.wf__btn {
position: absolute;
right: 12px;
bottom: 12px;
margin: 0;
padding: 4px 12px;
border: 0;
border-radius: 999px;
background: rgba(255, 255, 255, 0.85);
color: #17141a;
font: inherit;
font-weight: 500;
font-size: 12px;
line-height: 1.4;
cursor: pointer;
}
.wf__btn:focus-visible {
outline: 2px solid #ffffff;
outline-offset: 2px;
}
.wf__caption {
position: absolute;
left: 12px;
bottom: 12px;
max-width: 68%;
margin: 0;
padding: 4px 12px;
border-radius: 999px;
background: rgba(255, 255, 255, 0.85);
color: #17141a;
font-weight: 500;
font-size: 12px;
line-height: 1.4;
pointer-events: none;
}
@media (max-width: 340px) {
.wf__caption, .wf__btn {
font-size: 10px;
padding: 4px 8px;
}
.wf__status {
font-size: 10px;
}
}
@media (prefers-reduced-motion: reduce) {
.wf {
cursor: default;
}
}(function () {
const W = 480;
const H = 300;
const PI2 = Math.PI * 2;
const FIXED_DT = 16;
const IDLE_STEPS = 220;
const REDUCE_STEP_MS = 900;
const REDUCE_WARM_STEPS = 40;
const BTN_PAUSE = 'Pause';
const BTN_PLAY = 'Play';
const BTN_NEXT = 'Next moment';
// 파스텔 팔레트와 어두운 바탕 두 끝 색
const PINK = [255, 170, 196];
const MINT = [150, 226, 196];
const LILAC = [196, 176, 255];
const SKY_BLUE = [150, 214, 255];
const BUTTER = [255, 230, 150];
const CREAM = [255, 247, 230];
const INK = [23, 20, 26];
const BG_TOP = [24, 21, 40];
const BG_BOT = [48, 42, 78];
function clamp(v, lo, hi) { return v < lo ? lo : (v > hi ? hi : v); }
function lerp(a, b, k) { return a + (b - a) * k; }
function smooth(x) { const c = clamp(x, 0, 1); return c * c * (3 - 2 * c); }
function mix(a, b, k) { return [lerp(a[0], b[0], k), lerp(a[1], b[1], k), lerp(a[2], b[2], k)]; }
function rgba(c, a) { return 'rgba(' + Math.round(c[0]) + ',' + Math.round(c[1]) + ',' + Math.round(c[2]) + ',' + a.toFixed(3) + ')'; }
// 시드 고정 난수 — 같은 시드면 언제나 같은 수열 (선형 합동 방식)
function lcg(seed) {
let s = seed >>> 0;
return function () {
s = (Math.imul(s, 1664525) + 1013904223) >>> 0;
return s / 4294967296;
};
}
// 정수 하나와 시드로 0 이상 1 미만의 값을 만드는 해시 (같은 입력은 늘 같은 값)
function hash1(i, seed) {
let h = (Math.imul(i | 0, 374761393) + Math.imul(seed | 0, 668265263)) | 0;
h = Math.imul(h ^ (h >>> 13), 1274126177);
h ^= h >>> 16;
return (h >>> 0) / 4294967296;
}
// 사인 두 개를 음절마다 갈아 끼우고 엔벨로프를 씌운 합성 신호 (소리는 재생하지 않고 수치만 만든다)
function synth(n, seed) {
const rnd = lcg(seed);
const out = new Float32Array(n);
let i = 0;
let p1 = 0;
let p2 = 0;
let peak = 0.0001;
while (i < n) {
const len = 1800 + Math.floor(rnd() * 4200);
const amp = 0.18 + rnd() * 0.82;
const rest = rnd() < 0.18;
const f1 = 0.02 + rnd() * 0.09;
const f2 = f1 * (1.5 + rnd());
const stop = Math.min(n, i + len);
for (let k = i; k < stop; k += 1) {
const x = (k - i) / len;
const env = Math.min(1, x / 0.06) * Math.pow(1 - x, 0.8);
p1 += PI2 * f1;
p2 += PI2 * f2;
const tone = Math.sin(p1) * 0.7 + Math.sin(p2) * 0.3;
const gain = rest ? 0.03 : amp * env;
const v = gain * tone + (rnd() - 0.5) * 0.08 * (rest ? 0.4 : amp);
out[k] = v;
const a = Math.abs(v);
if (a > peak) {
peak = a;
}
}
i = stop;
}
const norm = 0.92 / peak;
for (let k = 0; k < n; k += 1) {
out[k] *= norm;
}
return out;
}
// 표본 구간 [a, b) 의 최솟값과 최댓값 — 결과는 rangeLo, rangeHi 에 둔다
let rangeLo = 0;
let rangeHi = 0;
function scanRange(sig, a, b) {
const from = Math.max(0, Math.floor(a));
const to = Math.min(sig.length, Math.max(from + 1, Math.ceil(b)));
let lo = 1e9;
let hi = -1e9;
for (let i = from; i < to; i += 1) {
const v = sig[i];
if (v < lo) {
lo = v;
}
if (v > hi) {
hi = v;
}
}
if (lo > hi) {
lo = 0;
hi = 0;
}
rangeLo = lo;
rangeHi = hi;
}
function paintBg(ctx, top, bot) {
const g = ctx.createLinearGradient(0, 0, 0, H);
g.addColorStop(0, rgba(top, 1));
g.addColorStop(1, rgba(bot, 1));
ctx.fillStyle = g;
ctx.fillRect(0, 0, W, H);
}
// 가짜 포인터 — 시연 동안 손이 움직이는 것처럼 보이게 그린다
function drawCursor(ctx, x, y, down) {
ctx.save();
ctx.translate(x, y);
ctx.beginPath();
ctx.moveTo(0, 0);
ctx.lineTo(0, 15);
ctx.lineTo(4, 11.5);
ctx.lineTo(7.5, 18);
ctx.lineTo(10, 16.8);
ctx.lineTo(6.6, 10.4);
ctx.lineTo(11.5, 10.2);
ctx.closePath();
ctx.fillStyle = rgba(CREAM, 1);
ctx.strokeStyle = rgba(INK, 1);
ctx.lineWidth = 1.4;
ctx.fill();
ctx.stroke();
if (down) {
ctx.beginPath();
ctx.arc(0, 0, 9, 0, PI2);
ctx.strokeStyle = rgba(PINK, 0.9);
ctx.lineWidth = 2;
ctx.stroke();
}
ctx.restore();
}
function boot(root, make) {
const canvasEl = root.querySelector('[data-role="canvas"]');
const statusEl = root.querySelector('[data-role="status"]');
const btnEl = root.querySelector('[data-role="btn"]');
if (!(canvasEl instanceof HTMLCanvasElement) || !statusEl || !(btnEl instanceof HTMLButtonElement)) {
return function () { };
}
const ctxOrNull = canvasEl.getContext('2d');
if (!ctxOrNull) {
return function () { };
}
const canvas = canvasEl;
const ctx = ctxOrNull;
const status = statusEl;
const btn = btnEl;
const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
const cleaners = [];
let paused = false;
let idle = IDLE_STEPS + 1;
let clock = 0;
let lastSayAt = -1e9;
let lastText = status.textContent || '';
let scene = null;
let rafId = 0;
let acc = 0;
let lastTs = -1;
function isAuto() { return !reduce && !paused && idle > IDLE_STEPS; }
function sync() {
const on = isAuto();
if (root.classList.contains('is-demo') !== on) {
root.classList.toggle('is-demo', on);
}
}
function fit() {
const r = canvas.getBoundingClientRect();
const dpr = window.devicePixelRatio || 1;
const cw = Math.max(1, Math.round(r.width * dpr));
const ch = Math.max(1, Math.round(r.height * dpr));
canvas.width = cw;
canvas.height = ch;
ctx.setTransform(cw / W, 0, 0, ch / H, 0, 0);
}
const host = {
ctx,
canvas,
root,
reduce,
touch() {
idle = 0;
sync();
},
auto: isAuto,
refresh() {
if (scene) {
scene.draw();
}
},
say(text) {
if (text === lastText) {
return;
}
if (!reduce && clock - lastSayAt < 250) {
return;
}
lastText = text;
lastSayAt = clock;
// 시연이 혼자 돌 때는 읽어 주지 않고, 사람이 만졌을 때만 알린다
status.setAttribute('aria-live', isAuto() ? 'off' : 'polite');
status.textContent = text;
},
local(e) {
const r = canvas.getBoundingClientRect();
return [clamp((e.clientX - r.left) * W / Math.max(1, r.width), 0, W), clamp((e.clientY - r.top) * H / Math.max(1, r.height), 0, H)];
},
listen(target, type, fn, opts) {
target.addEventListener(type, fn, opts);
cleaners.push(function () { target.removeEventListener(type, fn, opts); });
}
};
function advance(ms) {
if (!scene) {
return;
}
const n = Math.max(1, Math.round(ms / FIXED_DT));
for (let i = 0; i < n; i += 1) {
idle += 1;
clock += FIXED_DT;
scene.step();
}
}
function frame(ts) {
if (lastTs < 0) {
lastTs = ts;
}
const dt = Math.min(ts - lastTs, 160);
lastTs = ts;
if (!paused && scene) {
acc += dt;
while (acc >= FIXED_DT) {
idle += 1;
clock += FIXED_DT;
scene.step();
acc -= FIXED_DT;
}
sync();
scene.draw();
}
rafId = requestAnimationFrame(frame);
}
scene = make(host);
btn.textContent = reduce ? BTN_NEXT : BTN_PAUSE;
fit();
if (reduce) {
root.classList.remove('is-demo');
advance(REDUCE_WARM_STEPS * FIXED_DT);
}
scene.draw();
host.listen(btn, 'click', function () {
if (reduce) {
advance(REDUCE_STEP_MS);
host.refresh();
return;
}
paused = !paused;
btn.textContent = paused ? BTN_PLAY : BTN_PAUSE;
sync();
});
host.listen(window, 'resize', function () {
fit();
host.refresh();
});
if (!reduce) {
rafId = requestAnimationFrame(frame);
}
return function () {
cancelAnimationFrame(rafId);
for (let i = 0; i < cleaners.length; i += 1) {
cleaners[i]();
}
};
}
const TRIG_LEVEL = 0.15;
const HOLDOFF = 40;
const TRACE_GLOW = 6;
const TIME_DIV = 48;
const SHOW = 480;
const BUF_LEN = 2048;
const STEP_SAMPLES = 9;
const BASE_FREQ = 0.011;
const PANEL_H = 88;
const TOP_Y = 40;
const BOT_Y = 146;
const LEVEL_LIMIT = 0.7;
const TXT_TRIG = 'Triggered';
const TXT_FREE = 'Free-run';
const TXT_LEVEL = 'Trigger level';
// 입력 신호 — 주파수가 천천히 떠도는 비대칭 파형에 빠른 잔물결을 얹었다. 표본 번호만으로 값이 정해진다
function scopeSample(n) {
const phase = PI2 * BASE_FREQ * (n + 285.7 * (1 - Math.cos(0.0007 * n)));
return 0.62 * Math.sin(phase) + 0.28 * Math.sin(2 * phase + 0.9) + 0.09 * Math.sin(n * 0.83) + (hash1(n, 7) - 0.5) * 0.05;
}
// 최근 표본에서 레벨을 아래에서 위로 가로지르는 지점을 찾고, HOLDOFF 안쪽의 다음 에지는 버린다
function findTrigger(buf, level, holdoff, show) {
let kept = -1;
let found = -1;
for (let j = 1; j + show <= buf.length; j += 1) {
if (buf[j - 1] < level && buf[j] >= level) {
if (kept < 0 || j - kept >= holdoff) {
kept = j;
found = j;
}
}
}
return found;
}
function makeScopeScene(h) {
const buf = new Float32Array(BUF_LEN);
let n = BUF_LEN;
let level = TRIG_LEVEL;
let k = 0;
let dragging = false;
function fill() {
for (let i = 0; i < BUF_LEN; i += 1) {
buf[i] = scopeSample(n - BUF_LEN + i);
}
}
function setLevel(v) {
level = clamp(v, -LEVEL_LIMIT, LEVEL_LIMIT);
h.touch();
h.refresh();
}
h.listen(h.canvas, 'pointerdown', function (e) {
const pe = e;
dragging = true;
h.canvas.setPointerCapture(pe.pointerId);
setLevel((TOP_Y + PANEL_H / 2 - h.local(pe)[1]) / (PANEL_H / 2 * 0.85));
});
h.listen(h.canvas, 'pointermove', function (e) {
if (dragging) {
setLevel((TOP_Y + PANEL_H / 2 - h.local(e)[1]) / (PANEL_H / 2 * 0.85));
}
});
const drop = function () { dragging = false; };
h.listen(h.canvas, 'pointerup', drop);
h.listen(h.canvas, 'pointercancel', drop);
h.listen(h.canvas, 'keydown', function (e) {
const key = e.key;
if (key === 'ArrowUp') {
e.preventDefault();
setLevel(level + 0.05);
}
else if (key === 'ArrowDown') {
e.preventDefault();
setLevel(level - 0.05);
}
});
function panel(y0, from, label, accent, marker) {
const ctx = h.ctx;
const yc = y0 + PANEL_H / 2;
const amp = PANEL_H / 2 * 0.85;
ctx.fillStyle = rgba(INK, 0.45);
ctx.fillRect(0, y0, W, PANEL_H);
for (let x = TIME_DIV; x < W; x += TIME_DIV) {
ctx.fillStyle = rgba(CREAM, 0.1);
ctx.fillRect(x, y0, 1, PANEL_H);
}
ctx.fillStyle = rgba(CREAM, 0.18);
ctx.fillRect(0, yc, W, 1);
ctx.beginPath();
ctx.moveTo(0, yc);
for (let i = 0; i < SHOW; i += 1) {
ctx.lineTo(i, yc - buf[from + i] * amp);
}
ctx.lineTo(SHOW - 1, yc);
ctx.closePath();
ctx.fillStyle = rgba(accent, 0.16);
ctx.fill();
ctx.beginPath();
for (let i = 0; i < SHOW; i += 1) {
const y = yc - buf[from + i] * amp;
if (i === 0) {
ctx.moveTo(i, y);
}
else {
ctx.lineTo(i, y);
}
}
ctx.save();
ctx.shadowColor = rgba(accent, 0.9);
ctx.shadowBlur = TRACE_GLOW * ctx.getTransform().a;
ctx.strokeStyle = rgba(accent, 1);
ctx.lineWidth = 2;
ctx.stroke();
ctx.restore();
ctx.font = '11px sans-serif';
ctx.textAlign = 'right';
ctx.fillStyle = rgba(CREAM, 0.85);
ctx.fillText(label, W - 8, y0 + 14);
if (marker) {
const ly = yc - level * amp;
ctx.fillStyle = rgba(BUTTER, 0.85);
ctx.fillRect(0, ly, W, 1);
ctx.beginPath();
ctx.moveTo(0, ly - 5);
ctx.lineTo(9, ly);
ctx.lineTo(0, ly + 5);
ctx.closePath();
ctx.fill();
}
}
fill();
return {
step() {
k += 1;
n += STEP_SAMPLES;
fill();
if (h.auto() && !dragging) {
level = TRIG_LEVEL + 0.4 * Math.sin(k * 0.045);
}
},
draw() {
const ctx = h.ctx;
paintBg(ctx, BG_TOP, BG_BOT);
const at = findTrigger(buf, level, HOLDOFF, SHOW);
panel(TOP_Y, at < 0 ? BUF_LEN - SHOW : at, TXT_TRIG, MINT, true);
panel(BOT_Y, BUF_LEN - SHOW, TXT_FREE, PINK, false);
h.say(TXT_LEVEL + ': ' + level.toFixed(2));
}
};
}
boot(document.getElementById('wfRoot'), makeScopeScene);
})();import { useEffect, useRef } from "react";
import styles from "./WfScrollingScopeRisingEdgeTrigger.module.scss";
const W = 480;
const H = 300;
const PI2 = Math.PI * 2;
const FIXED_DT = 16;
const IDLE_STEPS = 220;
const REDUCE_STEP_MS = 900;
const REDUCE_WARM_STEPS = 40;
const BTN_PAUSE = '멈춤';
const BTN_PLAY = '재생';
const BTN_NEXT = '다음 순간';
type RGB = [number, number, number];
// 파스텔 팔레트와 어두운 바탕 두 끝 색
const PINK: RGB = [255, 170, 196];
const MINT: RGB = [150, 226, 196];
const LILAC: RGB = [196, 176, 255];
const SKY_BLUE: RGB = [150, 214, 255];
const BUTTER: RGB = [255, 230, 150];
const CREAM: RGB = [255, 247, 230];
const INK: RGB = [23, 20, 26];
const BG_TOP: RGB = [24, 21, 40];
const BG_BOT: RGB = [48, 42, 78];
interface Host {
ctx: CanvasRenderingContext2D;
canvas: HTMLCanvasElement;
root: HTMLElement;
reduce: boolean;
touch(): void;
auto(): boolean;
refresh(): void;
say(text: string): void;
local(e: MouseEvent): [number, number];
listen(target: EventTarget, type: string, fn: (e: Event) => void, opts?: AddEventListenerOptions): void;
}
interface Scene {
step(): void;
draw(): void;
}
function clamp(v: number, lo: number, hi: number): number { return v < lo ? lo : (v > hi ? hi : v); }
function lerp(a: number, b: number, k: number): number { return a + (b - a) * k; }
function smooth(x: number): number { const c = clamp(x, 0, 1); return c * c * (3 - 2 * c); }
function mix(a: RGB, b: RGB, k: number): RGB { return [lerp(a[0], b[0], k), lerp(a[1], b[1], k), lerp(a[2], b[2], k)]; }
function rgba(c: RGB, a: number): string { return 'rgba(' + Math.round(c[0]) + ',' + Math.round(c[1]) + ',' + Math.round(c[2]) + ',' + a.toFixed(3) + ')'; }
// 시드 고정 난수 — 같은 시드면 언제나 같은 수열 (선형 합동 방식)
function lcg(seed: number): () => number {
let s = seed >>> 0;
return function (): number {
s = (Math.imul(s, 1664525) + 1013904223) >>> 0;
return s / 4294967296;
};
}
// 정수 하나와 시드로 0 이상 1 미만의 값을 만드는 해시 (같은 입력은 늘 같은 값)
function hash1(i: number, seed: number): number {
let h = (Math.imul(i | 0, 374761393) + Math.imul(seed | 0, 668265263)) | 0;
h = Math.imul(h ^ (h >>> 13), 1274126177);
h ^= h >>> 16;
return (h >>> 0) / 4294967296;
}
// 사인 두 개를 음절마다 갈아 끼우고 엔벨로프를 씌운 합성 신호 (소리는 재생하지 않고 수치만 만든다)
function synth(n: number, seed: number): Float32Array {
const rnd = lcg(seed);
const out = new Float32Array(n);
let i = 0;
let p1 = 0;
let p2 = 0;
let peak = 0.0001;
while (i < n) {
const len = 1800 + Math.floor(rnd() * 4200);
const amp = 0.18 + rnd() * 0.82;
const rest = rnd() < 0.18;
const f1 = 0.02 + rnd() * 0.09;
const f2 = f1 * (1.5 + rnd());
const stop = Math.min(n, i + len);
for (let k = i; k < stop; k += 1) {
const x = (k - i) / len;
const env = Math.min(1, x / 0.06) * Math.pow(1 - x, 0.8);
p1 += PI2 * f1;
p2 += PI2 * f2;
const tone = Math.sin(p1) * 0.7 + Math.sin(p2) * 0.3;
const gain = rest ? 0.03 : amp * env;
const v = gain * tone + (rnd() - 0.5) * 0.08 * (rest ? 0.4 : amp);
out[k] = v;
const a = Math.abs(v);
if (a > peak) { peak = a; }
}
i = stop;
}
const norm = 0.92 / peak;
for (let k = 0; k < n; k += 1) { out[k] *= norm; }
return out;
}
// 표본 구간 [a, b) 의 최솟값과 최댓값 — 결과는 rangeLo, rangeHi 에 둔다
let rangeLo = 0;
let rangeHi = 0;
function scanRange(sig: Float32Array, a: number, b: number): void {
const from = Math.max(0, Math.floor(a));
const to = Math.min(sig.length, Math.max(from + 1, Math.ceil(b)));
let lo = 1e9;
let hi = -1e9;
for (let i = from; i < to; i += 1) {
const v = sig[i];
if (v < lo) { lo = v; }
if (v > hi) { hi = v; }
}
if (lo > hi) { lo = 0; hi = 0; }
rangeLo = lo;
rangeHi = hi;
}
function paintBg(ctx: CanvasRenderingContext2D, top: RGB, bot: RGB): void {
const g = ctx.createLinearGradient(0, 0, 0, H);
g.addColorStop(0, rgba(top, 1));
g.addColorStop(1, rgba(bot, 1));
ctx.fillStyle = g;
ctx.fillRect(0, 0, W, H);
}
// 가짜 포인터 — 시연 동안 손이 움직이는 것처럼 보이게 그린다
function drawCursor(ctx: CanvasRenderingContext2D, x: number, y: number, down: boolean): void {
ctx.save();
ctx.translate(x, y);
ctx.beginPath();
ctx.moveTo(0, 0);
ctx.lineTo(0, 15);
ctx.lineTo(4, 11.5);
ctx.lineTo(7.5, 18);
ctx.lineTo(10, 16.8);
ctx.lineTo(6.6, 10.4);
ctx.lineTo(11.5, 10.2);
ctx.closePath();
ctx.fillStyle = rgba(CREAM, 1);
ctx.strokeStyle = rgba(INK, 1);
ctx.lineWidth = 1.4;
ctx.fill();
ctx.stroke();
if (down) {
ctx.beginPath();
ctx.arc(0, 0, 9, 0, PI2);
ctx.strokeStyle = rgba(PINK, 0.9);
ctx.lineWidth = 2;
ctx.stroke();
}
ctx.restore();
}
function boot(root: HTMLElement, make: (h: Host) => Scene): () => void {
const canvasEl = root.querySelector('[data-role="canvas"]');
const statusEl = root.querySelector('[data-role="status"]');
const btnEl = root.querySelector('[data-role="btn"]');
if (!(canvasEl instanceof HTMLCanvasElement) || !statusEl || !(btnEl instanceof HTMLButtonElement)) {
return function (): void { /* 필요한 요소가 없으면 아무것도 하지 않는다 */ };
}
const ctxOrNull = canvasEl.getContext('2d');
if (!ctxOrNull) {
return function (): void { /* 2d 문맥이 없으면 아무것도 하지 않는다 */ };
}
const canvas: HTMLCanvasElement = canvasEl;
const ctx: CanvasRenderingContext2D = ctxOrNull;
const status: Element = statusEl;
const btn: HTMLButtonElement = btnEl;
const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
const cleaners: Array<() => void> = [];
let paused = false;
let idle = IDLE_STEPS + 1;
let clock = 0;
let lastSayAt = -1e9;
let lastText = status.textContent || '';
let scene: Scene | null = null;
let rafId = 0;
let acc = 0;
let lastTs = -1;
function isAuto(): boolean { return !reduce && !paused && idle > IDLE_STEPS; }
function sync(): void {
const on = isAuto();
if (root.classList.contains('is-demo') !== on) {
root.classList.toggle('is-demo', on);
}
}
function fit(): void {
const r = canvas.getBoundingClientRect();
const dpr = window.devicePixelRatio || 1;
const cw = Math.max(1, Math.round(r.width * dpr));
const ch = Math.max(1, Math.round(r.height * dpr));
canvas.width = cw;
canvas.height = ch;
ctx.setTransform(cw / W, 0, 0, ch / H, 0, 0);
}
const host: Host = {
ctx,
canvas,
root,
reduce,
touch(): void {
idle = 0;
sync();
},
auto: isAuto,
refresh(): void {
if (scene) { scene.draw(); }
},
say(text: string): void {
if (text === lastText) { return; }
if (!reduce && clock - lastSayAt < 250) { return; }
lastText = text;
lastSayAt = clock;
// 시연이 혼자 돌 때는 읽어 주지 않고, 사람이 만졌을 때만 알린다
status.setAttribute('aria-live', isAuto() ? 'off' : 'polite');
status.textContent = text;
},
local(e: MouseEvent): [number, number] {
const r = canvas.getBoundingClientRect();
return [clamp((e.clientX - r.left) * W / Math.max(1, r.width), 0, W), clamp((e.clientY - r.top) * H / Math.max(1, r.height), 0, H)];
},
listen(target: EventTarget, type: string, fn: (e: Event) => void, opts?: AddEventListenerOptions): void {
target.addEventListener(type, fn, opts);
cleaners.push(function (): void { target.removeEventListener(type, fn, opts); });
}
};
function advance(ms: number): void {
if (!scene) { return; }
const n = Math.max(1, Math.round(ms / FIXED_DT));
for (let i = 0; i < n; i += 1) {
idle += 1;
clock += FIXED_DT;
scene.step();
}
}
function frame(ts: number): void {
if (lastTs < 0) { lastTs = ts; }
const dt = Math.min(ts - lastTs, 160);
lastTs = ts;
if (!paused && scene) {
acc += dt;
while (acc >= FIXED_DT) {
idle += 1;
clock += FIXED_DT;
scene.step();
acc -= FIXED_DT;
}
sync();
scene.draw();
}
rafId = requestAnimationFrame(frame);
}
scene = make(host);
btn.textContent = reduce ? BTN_NEXT : BTN_PAUSE;
fit();
if (reduce) {
root.classList.remove('is-demo');
advance(REDUCE_WARM_STEPS * FIXED_DT);
}
scene.draw();
host.listen(btn, 'click', function (): void {
if (reduce) {
advance(REDUCE_STEP_MS);
host.refresh();
return;
}
paused = !paused;
btn.textContent = paused ? BTN_PLAY : BTN_PAUSE;
sync();
});
host.listen(window, 'resize', function (): void {
fit();
host.refresh();
});
if (!reduce) {
rafId = requestAnimationFrame(frame);
}
return function (): void {
cancelAnimationFrame(rafId);
for (let i = 0; i < cleaners.length; i += 1) { cleaners[i](); }
};
}
const TRIG_LEVEL = 0.15;
const HOLDOFF = 40;
const TRACE_GLOW = 6;
const TIME_DIV = 48;
const SHOW = 480;
const BUF_LEN = 2048;
const STEP_SAMPLES = 9;
const BASE_FREQ = 0.011;
const PANEL_H = 88;
const TOP_Y = 40;
const BOT_Y = 146;
const LEVEL_LIMIT = 0.7;
const TXT_TRIG = '트리거';
const TXT_FREE = '프리런';
const TXT_LEVEL = '트리거 레벨';
// 입력 신호 — 주파수가 천천히 떠도는 비대칭 파형에 빠른 잔물결을 얹었다. 표본 번호만으로 값이 정해진다
function scopeSample(n: number): number {
const phase = PI2 * BASE_FREQ * (n + 285.7 * (1 - Math.cos(0.0007 * n)));
return 0.62 * Math.sin(phase) + 0.28 * Math.sin(2 * phase + 0.9) + 0.09 * Math.sin(n * 0.83) + (hash1(n, 7) - 0.5) * 0.05;
}
// 최근 표본에서 레벨을 아래에서 위로 가로지르는 지점을 찾고, HOLDOFF 안쪽의 다음 에지는 버린다
function findTrigger(buf: Float32Array, level: number, holdoff: number, show: number): number {
let kept = -1;
let found = -1;
for (let j = 1; j + show <= buf.length; j += 1) {
if (buf[j - 1] < level && buf[j] >= level) {
if (kept < 0 || j - kept >= holdoff) {
kept = j;
found = j;
}
}
}
return found;
}
function makeScopeScene(h: Host): Scene {
const buf = new Float32Array(BUF_LEN);
let n = BUF_LEN;
let level = TRIG_LEVEL;
let k = 0;
let dragging = false;
function fill(): void {
for (let i = 0; i < BUF_LEN; i += 1) { buf[i] = scopeSample(n - BUF_LEN + i); }
}
function setLevel(v: number): void {
level = clamp(v, -LEVEL_LIMIT, LEVEL_LIMIT);
h.touch();
h.refresh();
}
h.listen(h.canvas, 'pointerdown', function (e: Event): void {
const pe = e as PointerEvent;
dragging = true;
h.canvas.setPointerCapture(pe.pointerId);
setLevel((TOP_Y + PANEL_H / 2 - h.local(pe)[1]) / (PANEL_H / 2 * 0.85));
});
h.listen(h.canvas, 'pointermove', function (e: Event): void {
if (dragging) {
setLevel((TOP_Y + PANEL_H / 2 - h.local(e as PointerEvent)[1]) / (PANEL_H / 2 * 0.85));
}
});
const drop = function (): void { dragging = false; };
h.listen(h.canvas, 'pointerup', drop);
h.listen(h.canvas, 'pointercancel', drop);
h.listen(h.canvas, 'keydown', function (e: Event): void {
const key = (e as KeyboardEvent).key;
if (key === 'ArrowUp') { e.preventDefault(); setLevel(level + 0.05); }
else if (key === 'ArrowDown') { e.preventDefault(); setLevel(level - 0.05); }
});
function panel(y0: number, from: number, label: string, accent: RGB, marker: boolean): void {
const ctx = h.ctx;
const yc = y0 + PANEL_H / 2;
const amp = PANEL_H / 2 * 0.85;
ctx.fillStyle = rgba(INK, 0.45);
ctx.fillRect(0, y0, W, PANEL_H);
for (let x = TIME_DIV; x < W; x += TIME_DIV) {
ctx.fillStyle = rgba(CREAM, 0.1);
ctx.fillRect(x, y0, 1, PANEL_H);
}
ctx.fillStyle = rgba(CREAM, 0.18);
ctx.fillRect(0, yc, W, 1);
ctx.beginPath();
ctx.moveTo(0, yc);
for (let i = 0; i < SHOW; i += 1) {
ctx.lineTo(i, yc - buf[from + i] * amp);
}
ctx.lineTo(SHOW - 1, yc);
ctx.closePath();
ctx.fillStyle = rgba(accent, 0.16);
ctx.fill();
ctx.beginPath();
for (let i = 0; i < SHOW; i += 1) {
const y = yc - buf[from + i] * amp;
if (i === 0) { ctx.moveTo(i, y); } else { ctx.lineTo(i, y); }
}
ctx.save();
ctx.shadowColor = rgba(accent, 0.9);
ctx.shadowBlur = TRACE_GLOW * ctx.getTransform().a;
ctx.strokeStyle = rgba(accent, 1);
ctx.lineWidth = 2;
ctx.stroke();
ctx.restore();
ctx.font = '11px sans-serif';
ctx.textAlign = 'right';
ctx.fillStyle = rgba(CREAM, 0.85);
ctx.fillText(label, W - 8, y0 + 14);
if (marker) {
const ly = yc - level * amp;
ctx.fillStyle = rgba(BUTTER, 0.85);
ctx.fillRect(0, ly, W, 1);
ctx.beginPath();
ctx.moveTo(0, ly - 5);
ctx.lineTo(9, ly);
ctx.lineTo(0, ly + 5);
ctx.closePath();
ctx.fill();
}
}
fill();
return {
step(): void {
k += 1;
n += STEP_SAMPLES;
fill();
if (h.auto() && !dragging) {
level = TRIG_LEVEL + 0.4 * Math.sin(k * 0.045);
}
},
draw(): void {
const ctx = h.ctx;
paintBg(ctx, BG_TOP, BG_BOT);
const at = findTrigger(buf, level, HOLDOFF, SHOW);
panel(TOP_Y, at < 0 ? BUF_LEN - SHOW : at, TXT_TRIG, MINT, true);
panel(BOT_Y, BUF_LEN - SHOW, TXT_FREE, PINK, false);
h.say(TXT_LEVEL + ': ' + level.toFixed(2));
}
};
}
export default function WfScrollingScopeRisingEdgeTrigger() {
const rootRef = useRef<HTMLDivElement | null>(null);
useEffect(() => {
const root = rootRef.current;
if (!root) return;
return boot(root, makeScopeScene);
}, []);
return (
<main className={styles.stage}>
<div className={`${styles.wf} is-demo`} ref={rootRef}>
<canvas className={styles.canvas} data-role="canvas" width={480} height={300} tabIndex={0} aria-label="상승 구간에서 트리거가 걸려 흔들림 없이 멈춰 보이는 흐르는 오실로스코프" />
<p className={styles.status} data-role="status" aria-live="polite">트리거 레벨</p>
<button className={styles.btn} data-role="btn" type="button">멈춤</button>
<p className={styles.caption}>상승 구간에서 트리거가 걸려 흔들림 없이 멈춰 보이는 흐르는 오실로스코프</p>
</div>
</main>
);
}06 A Rolling Oscilloscope Whose Rising-Edge Trigger Makes the Trace Hold Still — Measured area 32.302% · moving frames 23/23Original by GODRICH · SCSS and React ship in the zip · CSS Waveform: 9 Peak Columns and Trim Pickers
The post this demo lives in
CSS Waveform: 9 Peak Columns and Trim PickersA css waveform starts with squeezing thousands of samples into pixel columns — scene 01's min/max buckets and scene 05's See all demos in this post
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