Bug 264115 – An incorrect fallback font for Ahem returns where unicode-range is set.

• Component: Text
• Status: NEW

[ChangSeok Oh]

While I was investigating the failure of size-adjust-unicode-range-system-fallback.html [1], I found Mac port behaved unexpectedly to unicode-range. Please try the following HTML snippet.

```
<style>
@font-face {
  font-family: large-font;
  src: local(Ahem), url(/fonts/Ahem.ttf);
  size-adjust: 1000%;
  unicode-range: U+0020;
}

.test {
  font-family: large-font;
}
</style>
<span class="test">X</span>
```

The expected result is a small `X`, but Mac port shows a large square from Ahem.
Aside from the different sizes, unicode-range is set with U+0020 (i.e., space) so Ahem should be limited to only spaces.

When I tracked down this issue, I encountered that CTFontCreateForCharactersWithLanguageAndOption returned Ahem as a fallback for Ahem in lookupFallbackFont() at FontCacheCoreText.cpp. However, further investigation was not possible since I could not see the definition of CTFontCreateForCharactersWithLanguageAndOption.

Maybe, Apple folks want to look into this issue. FYI, GTK/WPE ports work fine.

[1] https://wpt.fyi/results/css/css-fonts/size-adjust-unicode-range-system-fallback.html?label=experimental&label=master&aligned

[Radar WebKit Bug Importer]

<rdar://problem/118199422>

[Alexey Proskuryakov]

Created attachment 469561 [details]
test case

[Alexey Proskuryakov]

Created attachment 469562 [details]
test case

[Alexey Proskuryakov]

The WPT link no longer shows the problem, as the test got changed to work around it. Attaching the original test.