[SOLVED] Certain ligatures do not work in chrome

Certain ligatures do not work in chrome

I noticed that google chrome does show only certain characters as ligatures. The following font contains the codepoints 👾,𝓐, and 📄. it also contains ligatures for the following codepoint sequences 📄👾, 📄𝓐, 𝓐📄.

Sequences containing the 𝓐 codepoint are not displayed as a ligature in Google Chrome:

@font-face {
  font-family: 'aliens';
  src: url('data:application/font-woff;base64,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');
}
td {
  font-family: 'aliens';
  letter-spacing: .000001em;
  font-variant-ligatures: contextual; 
  text-rendering: optimizeLegibility;
}

<table>
  <tr>
    <th>Symbol</th>
    <th>Description</th>
    <th>Does it work in Chrome?</th>
  </tr>
  <tr>
    <td>👾</td><td>ALIEN MONSTER</td><td>✔️</td>
  </tr>
  <tr>
    <td>📄</td><td>PAGE FACEING UP</td><td>✔️</td>
  </tr>
  <tr>
    <td>📄👾</td><td>ALIEN MONSTER ON PAGE</td><td>✔️</td>
  </tr>
  <tr>
    <td>𝓐</td><td>MATHEMATICAL BOLD SCRIPT CAPITAL A</td><td>✔️</td>
  </tr>
  <tr>
    <td>📄𝓐</td><td>A ON PAGE</td><td>❌</td>
  </tr>
  <tr>
    <td>𝓐📄</td><td>PAGE WITH A</td><td>❌</td>
  </tr>
</table>

Expected Result (Safari):

Actual Result in Chrome:

Safari & Firefox do not display the sequence 𝓐📄.

Are ligatures containing a 𝓐 codepoint invalid? Can ligatureS contain any sequences of codepoints? Is this a bug in chrome?

Solution

It appears the reason why Chrome doesn't apply the "A ON PAGE" ligature is that it split up the "A" and the "Page" into separate runs due to "A" being 'text' and "Page" being 'emoji'. In addition, even with that out of the way it seems that the "A" and "Page" will be considered different 'words', further breaking them into separate runs because blink believes that it can shape by word. Unfortunately, even adding a zwj doesn't seem to get around this.

Note that I see the "A ON PAGE" and associated ligature but do not see the "PAGE WITH A" glyph or ligature in the font, which may explain why neither Chrome nor Safari show this ligature.

I have opened a issue against Chromium with this information.