textpath-pathlength-zero-startoffset.html

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This test has a WPT meta file that expects 2 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /svg/text/scripted/textpath-pathlength-zero-startoffset.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<title>pathLength of zero and startOffset on a textPath</title>

<link rel="author" title="Karl Dubost" href="mailto:k_dubost@apple.com">

<link rel="help" href="https://w3c.github.io/svgwg/svg2-draft/paths.html#PathLengthAttribute">

<link rel="help" href="https://w3c.github.io/svgwg/svg2-draft/text.html#TextPathElementStartOffsetAttribute">

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<svg width="400" height="300">

  <defs>

    <path id="zero" d="M 10 50 L 390 50" pathLength="0"/>

    <path id="plain" d="M 10 50 L 390 50"/>

    <path id="half" d="M 10 50 L 390 50" pathLength="190"/>

  </defs>

  <text><textPath id="zero-abs" href="#zero" startOffset="0">ABCDEF</textPath></text>

  <text><textPath id="zero-pct" href="#zero" startOffset="50%">ABCDEF</textPath></text>

  <text><textPath id="plain-abs" href="#plain" startOffset="0">ABCDEF</textPath></text>

  <text><textPath id="plain-pct" href="#plain" startOffset="50%">ABCDEF</textPath></text>

  <text><textPath id="half-abs" href="#half" startOffset="95">ABCDEF</textPath></text>

</svg>

<script>

// The path runs from x=10 to x=390, so it measures 380 units: the start is x=10 and

// halfway is x=200. #half declares 190 for that same path, so its scaling factor is 2.

const el = (id) => document.getElementById(id);

const EPSILON = 1e-4;

const x = (id) => el(id).getStartPositionOfChar(0).x;

test(() => {

  assert_equals(el('plain-abs').getNumberOfChars(), 6, 'the string is laid out');

  assert_approx_equals(x('plain-abs'), 10, EPSILON, 'startOffset 0 is the path start');

  assert_approx_equals(x('plain-pct'), 200, EPSILON, '50% is halfway along');

  assert_approx_equals(x('half-abs'), 200, EPSILON, '95 declared units is halfway along');

}, 'control: startOffset and pathLength scaling both work on this path');

// "A value of zero is valid and must be treated as a scaling factor of infinity. A value

// of zero scaled infinitely must remain zero".

test(() => {

  assert_equals(el('zero-abs').getNumberOfChars(), 6, 'the string is laid out');

  assert_approx_equals(x('zero-abs'), 10, EPSILON);

}, 'a startOffset of 0 is unaffected by pathLength="0"');

// "'pathLength' has no effect on percentage distance-along-a-path calculations", and the

// scaling rule above applies to "any non-percentage value greater than zero", so a

// percentage never becomes infinite and stays measured against the real length.

test(() => {

  assert_equals(el('zero-pct').getNumberOfChars(), 6, 'the string is laid out');

  assert_approx_equals(x('zero-pct'), 200, EPSILON);

}, 'a percentage startOffset is unaffected by pathLength="0"');

test(() => {

  assert_approx_equals(x('zero-pct'), x('plain-pct'), EPSILON);

}, 'pathLength="0" places a percentage startOffset where no pathLength would');

</script>