add point trail to demo

demo/content.ts

@@ -30,7 +30,7 @@ import {BlobOptions} from "../public/blobs";
 import {interpolateBetween, interpolateBetweenSmooth} from "../internal/animate/interpolate";
 import {divide} from "../internal/animate/prepare";
 import {statefulAnimationGenerator} from "../internal/animate/state";
-import {CanvasKeyframe} from "../public/animate";
+import {CanvasCustomKeyframe, CanvasKeyframe, wigglePreset} from "../public/animate";
 
 const makePoly = (pointCount: number, radius: number, center: Coord): Point[] => {
     const angle = (2 * Math.PI) / pointCount;
@@ -830,3 +830,67 @@ addCanvas(1.8, (ctx, width, height) => {
         However if the animation is interrupted during interpolation there is no opportunity to
         clean up the extra points.`;
 });
+
+addCanvas(1.8, (ctx, width, height, animate) => {
+    const size = Math.min(width, height) * 0.8;
+    const center: Coord = {x: width * 0.5, y: height * 0.5};
+    const trailLength = 40;
+
+    const canvasPointGenerator = (keyframe: CanvasKeyframe | CanvasCustomKeyframe): Point[] => {
+        let points: Point[];
+        if ("points" in keyframe) {
+            points = keyframe.points;
+        } else {
+            points = genFromOptions(keyframe.blobOptions);
+        }
+        return mapPoints(points, ({curr}) => {
+            curr.x += center.x - size / 2;
+            curr.y += center.y - size / 2;
+            return curr;
+        });
+    };
+
+    const animation = statefulAnimationGenerator(
+        canvasPointGenerator,
+        (points: Point[]) => points as any ,
+        () => {},
+    )(Date.now);
+
+    wigglePreset(animation, {
+        extraPoints: 2,
+        randomness: 2,
+        seed: Math.random(),
+        size,
+    }, {}, {
+        speed: 2,
+    });
+
+    const pointHistory: Point[][] = [];
+    let renderCount = 0;
+    animate((frameTime) => {
+        renderCount++;
+        const points = animation.renderPoints();
+
+        if (renderCount % 2 === 0) {
+            pointHistory.push(points);
+        }
+        if (pointHistory.length > trailLength) {
+            pointHistory.shift();
+        }
+
+        for (let i = 0; i < pointHistory.length; i++) {
+            tempStyles(ctx, () => {
+                ctx.fillStyle = colors.secondary;
+                ctx.globalAlpha = i / pointHistory.length;
+            }, () => {
+                forPoints(pointHistory[i], ({curr}) => {
+                    drawPoint(ctx, curr, i / pointHistory.length);
+                });
+            })
+        }
+
+        drawClosed(ctx, points, true);
+    });
+
+    return `TODO`;
+});