From dc8cea6a059a934c45358449ee9dc8f3df3111ba Mon Sep 17 00:00:00 2001
From: Evert Prants <evert@lunasqu.ee>
Date: Sat, 29 Jul 2023 06:56:47 +0000
Subject: [PATCH] Add 'bezier.ts'

---
 bezier.ts | 223 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 223 insertions(+)
 create mode 100644 bezier.ts

diff --git a/bezier.ts b/bezier.ts
new file mode 100644
index 0000000..67fe88a
--- /dev/null
+++ b/bezier.ts
@@ -0,0 +1,223 @@
+import { vec2 } from 'gl-matrix';
+import './index.scss';
+
+const canvas = document.createElement('canvas');
+const ctx = canvas.getContext('2d')!;
+
+interface Bezier {
+  start: vec2;
+  controlS: vec2;
+  controlE: vec2;
+  end: vec2;
+}
+
+interface DrawBezier extends Bezier {
+  width: number;
+  color: string;
+}
+
+const cursor: vec2 = [0, 0];
+let movingPoint: vec2 | undefined;
+let currentCurve: Bezier | undefined;
+let currentPointIndex: number | undefined;
+let handleOffset: vec2 | undefined;
+let pointOffsets: vec2[] = [];
+let shiftDown = false;
+
+const drawCirclei = (x: number, y: number, radius: number) => {
+  ctx.beginPath();
+  ctx.arc(x, y, radius, 0, 2 * Math.PI, false);
+  ctx.fill();
+  ctx.stroke();
+};
+const drawCirclep = (point: vec2, radius: number) =>
+  drawCirclei(point[0], point[1], radius);
+
+const drawBezier = (bezier: DrawBezier) => {
+  ctx.strokeStyle = bezier.color;
+  ctx.lineWidth = bezier.width;
+  ctx.beginPath();
+  ctx.moveTo(bezier.start[0], bezier.start[1]);
+  ctx.bezierCurveTo(
+    bezier.controlS[0],
+    bezier.controlS[1],
+    bezier.controlE[0],
+    bezier.controlE[1],
+    bezier.end[0],
+    bezier.end[1]
+  );
+  ctx.stroke();
+};
+
+const inCircle = (point: vec2, circle: vec2, radius: number) =>
+  vec2.dist(point, circle) < radius;
+
+const drawHandle = (point: vec2, radius: number) => {
+  ctx.fillStyle = inCircle(cursor, point, radius + 1)
+    ? 'rgba(0, 0, 0, 0.15)'
+    : 'transparent';
+  ctx.strokeStyle = '#000';
+  ctx.lineWidth = 1;
+  drawCirclep(point, radius);
+};
+
+const lines: DrawBezier[] = [
+  {
+    start: [100, 100],
+    controlS: [250, 250],
+    controlE: [500, 250],
+    end: [650, 100],
+    width: 15,
+    color: '#ff11aa',
+  },
+];
+
+const getControlledBezier = () => {
+  let bezier: Bezier | undefined;
+  let point: vec2 | undefined;
+  let pindex: number | undefined;
+
+  for (const curve of lines) {
+    if (inCircle(cursor, curve.start, curve.width + 5 + 1)) {
+      bezier = curve;
+      point = curve.start;
+      pindex = 0;
+    }
+
+    if (inCircle(cursor, curve.end, curve.width + 5 + 1)) {
+      bezier = curve;
+      point = curve.end;
+      pindex = 3;
+    }
+
+    if (inCircle(cursor, curve.controlS, 10 + 1)) {
+      bezier = curve;
+      point = curve.controlS;
+      pindex = 1;
+    }
+
+    if (inCircle(cursor, curve.controlE, 10 + 1)) {
+      bezier = curve;
+      point = curve.controlE;
+      pindex = 2;
+    }
+  }
+
+  return { bezier, point, pindex };
+};
+
+const getHandleOffset = () => {
+  if (!currentCurve || !movingPoint) {
+    return;
+  }
+
+  if (currentPointIndex === 1) {
+    handleOffset = vec2.sub(
+      vec2.create(),
+      currentCurve.start,
+      currentCurve.controlS
+    );
+  } else if (currentPointIndex === 2) {
+    handleOffset = vec2.sub(
+      vec2.create(),
+      currentCurve.end,
+      currentCurve.controlE
+    );
+  } else {
+    handleOffset = undefined;
+
+    if (currentPointIndex === 0 || currentPointIndex === 3) {
+      pointOffsets = [
+        vec2.sub(vec2.create(), currentCurve.start, movingPoint),
+        vec2.sub(vec2.create(), currentCurve.controlS, movingPoint),
+        vec2.sub(vec2.create(), currentCurve.controlE, movingPoint),
+        vec2.sub(vec2.create(), currentCurve.end, movingPoint),
+      ];
+    }
+  }
+};
+
+const relativeMove = () => {
+  if (!currentCurve || !movingPoint) {
+    return;
+  }
+
+  if (currentPointIndex === 1) {
+    vec2.add(currentCurve.start, movingPoint, handleOffset!);
+  } else if (currentPointIndex === 2) {
+    vec2.add(currentCurve.end, movingPoint, handleOffset!);
+  } else {
+    vec2.add(currentCurve.start, pointOffsets[0], movingPoint);
+    vec2.add(currentCurve.controlS, pointOffsets[1], movingPoint);
+    vec2.add(currentCurve.controlE, pointOffsets[2], movingPoint);
+    vec2.add(currentCurve.end, pointOffsets[3], movingPoint);
+  }
+};
+
+function resize() {
+  canvas.width = window.innerWidth;
+  canvas.height = window.innerHeight;
+}
+
+function draw() {
+  ctx.clearRect(0, 0, canvas.width, canvas.height);
+  ctx.lineCap = 'round';
+  lines.forEach((item) => {
+    drawBezier(item);
+    drawHandle(item.start, item.width + 5);
+    drawHandle(item.end, item.width + 5);
+    drawHandle(item.controlS, 10);
+    drawHandle(item.controlE, 10);
+  });
+}
+
+function loop() {
+  requestAnimationFrame(loop);
+  draw();
+}
+
+canvas.addEventListener('mousemove', (ev) => {
+  cursor[0] = ev.clientX;
+  cursor[1] = ev.clientY;
+
+  if (movingPoint) {
+    if (shiftDown && currentCurve) {
+      getHandleOffset();
+    }
+
+    vec2.copy(movingPoint, cursor);
+
+    if (shiftDown && currentCurve) {
+      relativeMove();
+    }
+  }
+});
+
+canvas.addEventListener('mousedown', (ev) => {
+  const { point, bezier, pindex } = getControlledBezier();
+  if (point && bezier) {
+    movingPoint = point;
+    currentCurve = bezier;
+    currentPointIndex = pindex;
+  }
+});
+
+canvas.addEventListener('mouseup', () => {
+  movingPoint = undefined;
+});
+
+window.addEventListener('keydown', (ev) => {
+  if (ev.key === 'Shift') {
+    shiftDown = true;
+  }
+});
+
+window.addEventListener('keyup', (ev) => {
+  if (ev.key === 'Shift') {
+    shiftDown = false;
+  }
+});
+resize();
+window.addEventListener('resize', resize);
+document.body.appendChild(canvas);
+loop();