@meta2d/core/src/grid/defaultGrid.js

@meta2d/core: Powerful, Beautiful, Simple, Open - Web-Based 2D At Its Best .

export function defaultGridDrawer(ctx, { area, align, size, color, rotate }, mousePos) {
    ctx.lineWidth = 1;
    ctx.strokeStyle = color;
    if (rotate) {
        const radian1 = (rotate * Math.PI) / 180;
        const radian2 = radian1 + Math.PI / 2;
        const normal1 = { x: Math.sin(radian1), y: -Math.cos(radian1) };
        const normal2 = { x: Math.sin(radian2), y: -Math.cos(radian2) };
        drawPreciseLines(ctx, area, size, normal1, radian1);
        drawPreciseLines(ctx, area, size, normal2, radian2);
    }
    else {
        const m = align.x / size;
        const n = align.y / size;
        const offset = size * 10;
        const newX = align.x - Math.ceil(m) * size;
        const newY = align.y - Math.ceil(n) * size;
        const endX = area.x + area.width + offset;
        const endY = area.y + area.height + offset;
        ctx.beginPath();
        for (let i = newX; i <= endX; i += size) {
            ctx.moveTo(i, newY);
            ctx.lineTo(i, area.y + area.height + offset);
        }
        for (let i = newY; i <= endY; i += size) {
            ctx.moveTo(newX, i);
            ctx.lineTo(area.x + area.width + offset, i);
        }
        ctx.stroke();
    }
    return false;
}
function drawPreciseLines(ctx, area, spacing, normal, angle) {
    const corners = [
        { x: area.x, y: area.y },
        { x: area.x + area.width, y: area.y },
        { x: area.x + area.width, y: area.y + area.height },
        { x: area.x, y: area.y + area.height },
    ];
    let minProjection = Infinity;
    let maxProjection = -Infinity;
    corners.forEach((corner) => {
        const proj = corner.x * normal.x + corner.y * normal.y;
        minProjection = Math.min(minProjection, proj);
        maxProjection = Math.max(maxProjection, proj);
    });
    const lineCount = Math.ceil((maxProjection - minProjection) / spacing);
    ctx.beginPath();
    for (let i = 0; i <= lineCount; i++) {
        const d = minProjection + i * spacing;
        let points = [];
        for (let j = 0; j < corners.length; j++) {
            const p1 = corners[j];
            const p2 = corners[(j + 1) % corners.length];
            const denom = normal.x * (p2.y - p1.y) - normal.y * (p2.x - p1.x);
            if (Math.abs(denom) > 1e-6) {
                const t = (d - p1.x * normal.x - p1.y * normal.y) /
                    (normal.x * (p2.x - p1.x) + normal.y * (p2.y - p1.y));
                if (t >= 0 && t <= 1) {
                    const x = p1.x + t * (p2.x - p1.x);
                    const y = p1.y + t * (p2.y - p1.y);
                    points.push({ x, y });
                }
            }
        }
        if (points.length >= 2) {
            ctx.moveTo(points[0].x, points[0].y);
            ctx.lineTo(points[1].x, points[1].y);
        }
    }
    ctx.stroke();
}
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