Lasso Selection

This example demonstrates how to implement a lasso selection tool that allows users to select multiple nodes by drawing a freehand selection area. The component features:

Lasso Drawing: Draw freehand selection areas using pointer events
Partial/Full Selection: Toggle between selecting nodes partially or fully enclosed by the lasso
Visual Feedback: Real-time visual feedback while drawing the selection area
Canvas Rendering: Uses HTML5 Canvas for smooth drawing performance


import getStroke from 'perfect-freehand';
 
export const pathOptions = {
  size: 7,
  thinning: 0.5,
  smoothing: 0.5,
  streamline: 0.5,
  easing: (t: number) => t,
  start: {
    taper: 0,
    easing: (t: number) => t,
    cap: true,
  },
  end: {
    taper: 0.1,
    easing: (t: number) => t,
    cap: true,
  },
};
 
export function getSvgPathFromStroke(stroke: number[][]) {
  if (!stroke.length) return '';
 
  const d = stroke.reduce(
    (acc, [x0, y0], i, arr) => {
      const [x1, y1] = arr[(i + 1) % arr.length];
      acc.push(x0, y0, ',', (x0 + x1) / 2, (y0 + y1) / 2);
      return acc;
    },
    ['M', ...stroke[0], 'Q'],
  );
 
  d.push('Z');
  return d.join(' ');
}
 
export function pointsToPath(points: [number, number, number][], zoom = 1) {
  const stroke = getStroke(points, {
    ...pathOptions,
    size: pathOptions.size * zoom,
  });
  return getSvgPathFromStroke(stroke);
}