fabric/src/util/misc/projectStroke/index.ts

Object model for HTML5 canvas, and SVG-to-canvas parser. Backed by jsdom and node-canvas.

import { Point, type XY } from '../../../Point';
import { findIndexRight } from '../../internals/findRight';
import { StrokeLineCapProjections } from './StrokeLineCapProjections';
import { StrokeLineJoinProjections } from './StrokeLineJoinProjections';
import type { TProjection, TProjectStrokeOnPointsOptions } from './types';

export * from './types';

/**
 *
 * Used to calculate object's bounding box
 *
 * @see https://github.com/fabricjs/fabric.js/pull/8344
 *
 */
export const projectStrokeOnPoints = (
  points: XY[],
  options: TProjectStrokeOnPointsOptions,
  openPath = false,
): TProjection[] => {
  const projections: TProjection[] = [];

  if (points.length === 0) {
    return projections;
  }

  // first we remove duplicate neighboring points
  const reduced = points.reduce(
    (reduced, point) => {
      if (!reduced[reduced.length - 1].eq(point)) {
        reduced.push(new Point(point));
      }
      return reduced;
    },
    [new Point(points[0])],
  );

  if (reduced.length === 1) {
    openPath = true;
  } else if (!openPath) {
    // remove points from end in case they equal the first point
    // in order to correctly project the first point
    const start = reduced[0];
    const index = findIndexRight(reduced, (point) => !point.eq(start));
    reduced.splice(index + 1);
  }

  reduced.forEach((A, index, points) => {
    let B: XY, C: XY;
    if (index === 0) {
      C = points[1];
      B = openPath ? A : points[points.length - 1];
    } else if (index === points.length - 1) {
      B = points[index - 1];
      C = openPath ? A : points[0];
    } else {
      B = points[index - 1];
      C = points[index + 1];
    }

    if (openPath && points.length === 1) {
      projections.push(
        ...new StrokeLineCapProjections(A, A, options).project(),
      );
    } else if (openPath && (index === 0 || index === points.length - 1)) {
      projections.push(
        ...new StrokeLineCapProjections(
          A,
          index === 0 ? C : B,
          options,
        ).project(),
      );
    } else {
      projections.push(
        ...new StrokeLineJoinProjections(A, B, C, options).project(),
      );
    }
  });

  return projections;
};