Intermittent PASS in /css/css-fonts/font-feature-settings-descriptor-01.html #45418

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1. Loirooriol

   added

   I-intermittentProblem reproduces intermittently.Problem reproduces intermittently.

   on Jun 5, 2026
2. simonwuelker commented on Jun 5, 2026

   

   simonwuelker

   on Jun 5, 2026

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   servo/tests/wpt/tests/css/css-fonts/font-feature-settings-descriptor-01.html

   Lines 11 to 19 in 8b72f6c

   	@font-face {
   	font-family: fwf;
   	src: url(support/fonts/FontWithFancyFeatures.otf);
   	}
   	@font-face {
   	font-family: fwf2;
   	src: url(support/fonts/FontWithFancyFeatures.otf);
   	font-feature-settings: "liga" on, "clig" on, "calt" on, "hlig" on, "dlig" on, "onum" on, "smcp" on, "jp90" on;
   	}

   Probably something related to the font cache, where whichever ·@font-face loads first wins. Will investigate later today.
3. simonwuelker commented on Jun 5, 2026

   

   simonwuelker

   on Jun 5, 2026

   Last edited by simonwuelker

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   The problem is that both fonts get the same cache entry here:

   servo/components/fonts/font_context.rs

   Lines 257 to 264 in 8a33aaa

   	let cache_key = FontCacheKey {
   	font_identifier: font_template.identifier(),
   	font_descriptor: font_descriptor.clone(),
   	};
   	if let Some(font) = self.fonts.read().get(&cache_key).cloned() {
   	return font;
   	}

   , so the test always uses either only fwf or only fwf2 (whichever one loads first and is used during the first restyle).
4. mrobinson commented on Jun 5, 2026

   

   mrobinson

   on Jun 5, 2026

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   More investigation is probably necessary to know why this particular template was returned from

   servo/components/fonts/font_store.rs

   Line 217 in c14368c

   pub fn find_for_descriptor(

   .

   I've seen similar flakes. I think there are two solutions to problems like this:

   • Let the font cache / resolution code have the concept of a defined font that isn't loaded yet. That way the font matcher can match the loading font, but not understand that it shouldn't use another, similar one.
   • Wait to make fonts available until all of the ones that would match together are loaded (a workaround, but maybe easier).

   In addition, maybe FontDescriptors need to be extended with more information to avoid a mismatch in this case.
5. simonwuelker commented on Jun 5, 2026

   

   simonwuelker

   on Jun 5, 2026

   Last edited by simonwuelker

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   More investigation is probably necessary to know why this particular template was returned from

   The templates for both fonts are correct (and are correctly selected for their respective text ranges), but when the FontGroupFamilyTemplates try and load their font then the font cache thinks they are the same and gives them the same Font object.
6. goransh-walia commented on Jun 7, 2026

   

   goransh-walia

   on Jun 7, 2026 · Hidden as low-quality

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7. jdm commented on Jun 7, 2026

   

   jdm

   on Jun 7, 2026

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   @goransh-buh Did you mean to comment on another issue? I don't see how your comment is related to this one.