packed-points.ts

import { TAU } from "@thi.ng/math";
import type { IObjectOf } from "@thi.ng/api";

export const packedPoints = (
    ctx: CanvasRenderingContext2D,
    attribs: IObjectOf<any>,
    opts: IObjectOf<any>,
    pts: ArrayLike<number>
) => {
    let v: any;
    if ((v = attribs.fill) && v !== "none") {
        __drawPoints(ctx, opts, pts, "fill", "fillRect");
    }
    if ((v = attribs.stroke) && v !== "none") {
        __drawPoints(ctx, opts, pts, "stroke", "strokeRect");
    }
};

const __drawPoints = (
    ctx: CanvasRenderingContext2D,
    opts: IObjectOf<any>,
    pts: ArrayLike<number>,
    cmd: "fill" | "stroke",
    cmdR: "fillRect" | "strokeRect"
) => {
    const { start, cstride, estride, size } = {
        start: 0,
        cstride: 1,
        estride: 2,
        size: 1,
        ...opts
    };
    let num =
        opts && opts.num != null
            ? opts.num
            : ((pts.length - start) / estride) | 0;
    if (opts.shape === "circle") {
        for (let i = start; --num >= 0; i += estride) {
            ctx.beginPath();
            ctx.arc(pts[i], pts[i + cstride], size, 0, TAU);
            ctx[cmd]();
        }
    } else {
        const r = size / 2;
        for (let i = start; --num >= 0; i += estride) {
            ctx[cmdR](pts[i] - r, pts[i + cstride] - r, size, size);
        }
    }
};