Text layout algorithm: Incorrect "anchored chunk" handling

[tkent-google]

Specification: "3. Resolve character positioning" in https://svgwg.org/svg2-draft/text.html#TextLayoutAlgorithm

If an implementation follows the current algorithm, following two <text>s should show different results because "anchored chunk" flags for all characters are cleared in the second one though they are identical in major browsers.

  <text x="100 100 100" y="50 95 140"
	style="font-size: 42px; text-anchor: middle">I❤SVG</text>

  <text x="100 100 100" y="50 95 140"
	style="font-size: 42px; text-anchor: middle"><tspan>I❤SVG</tspan></text>

What's wrong

Let's trace the algorithm with the second example. Assume that result[0] is for 'I', result[1] is for '❤', result[2] is for 'S'.

• Procedure resolve character positioning for <text> sets the "anchored chunk" flags of result[0], result[1], and result[2] to true. ( 3.2.1.6.1.1 if i < new_check_count, then set the "anchored chunk" flag of result[index + j] to true. Else set the flag to false.)
• Then we enter resolve character positioning for <tspan>.
• It sets the "anchored chunk" flags of result[0], result[1], and result[2] to false because new_chunk_count is 0.

The current algorithm also overwrites "anchored chunk" flag set by '2.3. If the character at index i corresponds to a typographic character at the beginning of a line, then set the "anchored chunk" flag of result[i] to true.' and '3.2.2.2. Set the "anchored chunk" flag of result[index] to true.'

I think an easy fix would be

• Do not set false at 3.2.1.6.1.1
• At 3.2.2.2, set result[i] for all of descendant characters of <textPath> to false except for result[index].