Obtaining length of some Arc can exceed maximum call stack

[mryellow]

M 216.1027854225359 271.1209756706295 A 46.283096266347606 28.725390201836586 2.166914683186652 0 1 287.49723659993464 261.4021001840497

M 164.16806031012334 277.88997477304815 A 112.78408575681235 76.52010425131027 -175.93248043341987 1 1 158.42630883977398 299.49871866124164

RangeError: Maximum call stack size exceeded

I believe the issue may be related to early return of an estimate being delayed too deeply into the recursive length call stack.

Perhaps this 0.00001 constant is the wrong size. Perhaps a count of call stack depth is required. Or perhaps simply a try/catch where the result is returned on RangeError.

svgdom/src/utils/pathUtils.js

Line 351 in 0a2a9c9

if (len1 + len2 - length < 0.00001) {

[mryellow]

Succeeds:

• A 10 10 0 0 0 100 100
• A 10 10 0 0 0 100 200
• A 10 10 0 0 0 100 250

Fails:

• A 10 10 1 0 0 100 100
• A 10 10 1 0 0 100 200
• A 10 10 0 0 0 100 251

[mryellow]

/* global describe, it */

import { createSVGDocument } from '../main-module.js'
import assert from 'assert'

describe('arc length', () => {
  it('obtaining arc length should not result in RangeError', () => {
    const svgDoc = createSVGDocument()

    const el = svgDoc.createElement('path');
    // (rx ry x-axis-rotation large-arc-flag sweep-flag x y)+
    //el.setAttribute('d', 'M 216.1027854225359 271.1209756706295 A 46.283096266347606 28.725390201836586 2.166914683186652 0 1 287.49723659993464 261.4021001840497');
    //el.setAttribute('d', 'M 216 271 A 46 28 2 0 1 287 261');
    //el.setAttribute('d', 'A 46 28 2 0 1 287 261');
    el.setAttribute('d', 'A 10 10 0 0 0 100 251');
    svgDoc.documentElement.appendChild(el);

    const length = svgDoc.querySelectorAll('svg path')[0].getTotalLength();
    assert(length > 0);
  })
})

[mryellow]

Rather than bisecting over and over again svg-path-properties decides ahead of time how many segments to limit itself to.

https://github.com/rveciana/svg-path-properties/blob/40d42d50729b2560dcfda2cf36e5d78b049a4f73/src/arc.ts#L253-L254

[Fuzzyma]

Deciding ahead of time how many segments to use can lead to unprecise approximations for really large arcs. But yes, this is a problem and a bug. Just not sure how to solve it properly

[mryellow]

Could always decouple with setTimeout and return a promise... Though it seems a little out-of-place here.

[Fuzzyma]

That wouldnt work since this function is expected to return directly. Cant break user expectation here. I am not following dom standards to the max but this lib still remains a drop in replacement for a real dom :D

[mryellow]

I'd think return what you have on a RangeError though the way it's dividing and recusing down there isn't really a "what you have".

Haven't gone back and reviewed what scopes are available but could maybe keep a count of recursions somewhere and return before the error.

[Fuzzyma]

or maybe rewrite the recursion as a while loop (which should be possible if it is tail call optimizable).