From 59e2416b610c45561ba3ffd8a8c8eaed76e9302b Mon Sep 17 00:00:00 2001
From: Andreas Kling <andreas@ladybird.org>
Date: Fri, 23 May 2025 14:03:40 +0200
Subject: [PATCH] LibWeb: Handle format(woff-variations) etc in @font-face src
 values

"format(woff-variations)" and pals are supposed to expand like so:
"format(woff) tech(variations)".

However, since we don't support tech() yet, this patch just adds a small
hack where we still treat "woff-variations" as "woff" so that fonts
load and get used, even if we don't make use of the variations yet.
---
 Libraries/LibWeb/CSS/Parser/ValueParsing.cpp          |  7 +++++++
 .../css/css-fonts/format-specifiers-variations.txt    | 11 +++++------
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/Libraries/LibWeb/CSS/Parser/ValueParsing.cpp b/Libraries/LibWeb/CSS/Parser/ValueParsing.cpp
index 3ff8e271f83..6d2ae2627b1 100644
--- a/Libraries/LibWeb/CSS/Parser/ValueParsing.cpp
+++ b/Libraries/LibWeb/CSS/Parser/ValueParsing.cpp
@@ -3874,6 +3874,7 @@ RefPtr<StringStyleValue const> Parser::parse_opentype_tag_value(TokenStream<Comp
     return string_value;
 }
 
+// https://drafts.csswg.org/css-fonts/#font-face-src-parsing
 RefPtr<FontSourceStyleValue const> Parser::parse_font_source_value(TokenStream<ComponentValue>& tokens)
 {
     // <font-src> = <url> [ format(<font-format>)]? [ tech( <font-tech>#)]? | local(<family-name>)
@@ -3919,6 +3920,12 @@ RefPtr<FontSourceStyleValue const> Parser::parse_font_source_value(TokenStream<C
             return nullptr;
         }
 
+        // FIXME: Some of the formats support an optional "-variations" suffix that's really supposed to map to tech(variations).
+        //        Once we support tech(*), we should ensure this propagates correctly.
+        if (format_name.is_one_of("woff2-variations"sv, "woff-variations"sv, "truetype-variations"sv, "opentype-variations"sv)) {
+            format_name = MUST(format_name.to_string().substring_from_byte_offset(0, format_name.bytes().size() - strlen("-variations")));
+        }
+
         if (!font_format_is_supported(format_name)) {
             dbgln_if(CSS_PARSER_DEBUG, "CSSParser: font source format({}) not supported; skipping.", format_name);
             return nullptr;
diff --git a/Tests/LibWeb/Text/expected/wpt-import/css/css-fonts/format-specifiers-variations.txt b/Tests/LibWeb/Text/expected/wpt-import/css/css-fonts/format-specifiers-variations.txt
index fb320e64002..c6bf3b94716 100644
--- a/Tests/LibWeb/Text/expected/wpt-import/css/css-fonts/format-specifiers-variations.txt
+++ b/Tests/LibWeb/Text/expected/wpt-import/css/css-fonts/format-specifiers-variations.txt
@@ -2,16 +2,15 @@ Harness status: OK
 
 Found 48 tests
 
-44 Pass
-4 Fail
+48 Pass
 Pass	Load Ahem with format woff
 Pass	Load Ahem with format truetype
 Pass	Load Ahem with format opentype
 Pass	Load Ahem with format woff2
-Fail	Load Ahem with format woff-variations
-Fail	Load Ahem with format truetype-variations
-Fail	Load Ahem with format opentype-variations
-Fail	Load Ahem with format woff2-variations
+Pass	Load Ahem with format woff-variations
+Pass	Load Ahem with format truetype-variations
+Pass	Load Ahem with format opentype-variations
+Pass	Load Ahem with format woff2-variations
 Pass	Do not load Ahem with format xyzwoff
 Pass	Do not load Ahem with format xyztruetype
 Pass	Do not load Ahem with format xyzopentype